confirmation of results for the analytes listed in Tables 1 and 2
using the extract produced by this method, and Method 1699
(Reference 18) provides high resolution GC/MS conditions for
qualitative confirmation of results using the original sample. When
such methods are used to confirm the identifications of the target
analytes, the quantitative results should be derived from the
procedure with the calibration range and sensitivity that are most
appropriate for the intended application.
    1.4 The large number of analytes in Tables 1 and 2 makes testing
difficult if all analytes are determined simultaneously. Therefore,
it is necessary to determine and perform quality control (QC) tests
for the ``analytes of interest'' only. The analytes of interest are
those required to be determined by a regulatory/control authority or
in a permit, or by a client. If a list of analytes is not specified,
the analytes in Table 1 must be determined, at a minimum, and QC
testing must be performed for these analytes. The analytes in Table
1 and some of the analytes in Table 2 have been identified as Toxic
Pollutants (40 CFR 401.15), expanded to a list of Priority
Pollutants (40 CFR part 423, appendix A).
    1.5 In this revision to Method 608, Chlordane has been listed as
the alpha- and gamma- isomers in Table 1. Reporting may be by the
individual isomers, or as the sum of the concentrations of these
isomers, as requested or required by a regulatory/control authority
or in a permit. Technical Chlordane is listed in Table 2 and may be
used in cases where historical reporting has only been the Technical
Chlordane. Toxaphene and the PCBs have been moved from Table 1 to
Table 2 (Additional Analytes) to distinguish these analytes from the
analytes required in quality control tests (Table 1). QC acceptance
criteria for Toxaphene and the PCBs have been retained in Table 4
and may continue to be applied if desired, or if these analytes are
requested or required by a regulatory/control authority or in a
permit. Method 1668C (Reference 17) may be useful for determination
of PCBs as individual chlorinated biphenyl congeners, and Method
1699 (Reference 18) may be useful for determination of the
pesticides listed in this method. However, at the time of writing of
this revision, Methods 1668C and 1699 had not been approved for use
at 40 CFR part 136.
    1.6 Method detection limits (MDLs; Reference 3) for the analytes
in Tables 1 and some of the analytes in Table 2 are listed in those
tables. These MDLs were determined in reagent water (Reference 3).
Advances in analytical technology, particularly the use of capillary
(open-tubular) columns, allowed laboratories to routinely achieve
MDLs for the analytes in this method that are 2-10 times lower than
those in the version promulgated in 1984. The MDL for an analyte in
a specific wastewater may differ from those listed, depending upon
the nature of interferences in the sample matrix.
    1.6.1 EPA has promulgated this method at 40 CFR part 136 for use
in wastewater compliance monitoring under the National Pollutant
Discharge Elimination System (NPDES). The data reporting practices
described in section 15.6 are focused on such monitoring needs and
may not be relevant to other uses of the method.
    1.6.2 This method includes ``reporting limits'' based on EPA's
``minimum level'' (ML) concept (see the glossary in section 23).
Tables 1 and 2 contain MDL values and ML values for many of the
analytes.
    1.7 The separatory funnel and continuous liquid-liquid sample
extraction and concentration steps in this method are essentially
the same as those steps in Methods 606, 609, 611, and 612. Thus, a
single sample may be extracted to measure the analytes included in
the scope of each of these methods. Samples may also be extracted
using a disk-based solid-phase extraction (SPE) procedure developed
by the 3M Corporation and approved by EPA as an Alternate Test
Procedure (ATP) for wastewater analyses in 1995 (Reference 20).
    1.8 This method is performance-based. It may be modified to
improve performance (e.g., to overcome interferences or improve the
accuracy of results) provided all performance requirements are met.
    1.8.1 Examples of allowed method modifications are described at
40 CFR 136.6. Other examples of allowed modifications specific to
this method are described in section 8.1.2.
    1.8.2 Any modification beyond those expressly permitted at 40
CFR 136.6 or in section 8.1.2 of this method shall be considered a
major modification subject to application and approval of an
alternate test procedure under 40 CFR 136.4 and 136.5.
    1.8.3 For regulatory compliance, any modification must be
demonstrated to produce results equivalent or superior to results
produced by this method when applied to relevant wastewaters
(section 8.1.2).
    1.9 This method is restricted to use by or under the supervision
of analysts experienced in the use of GC/HSD. The laboratory must
demonstrate the ability to generate acceptable results with this
method using the procedure in section 8.2.
    1.10 Terms and units of measure used in this method are given in
the glossary at the end of the method.

2. Summary of Method

    2.1 A measured volume of sample, the amount required to meet an
MDL or reporting limit (nominally 1-L), is extracted with methylene
chloride using a separatory funnel, a continuous liquid/liquid
extractor, or disk-based solid-phase extraction equipment. The
extract is dried and concentrated for cleanup, if required. After
cleanup, or if cleanup is not required, the extract is exchanged
into an appropriate solvent and concentrated to the volume necessary
to meet the required compliance or detection limit, and analyzed by
GC/HSD.
    2.2 Qualitative identification of an analyte in the extract is
performed using the retention times on dissimilar GC columns.
Quantitative analysis is performed using the peak areas or peak
heights for the analyte on the dissimilar columns with either the
external or internal standard technique.
    2.3 Florisil[supreg], alumina, a C18 solid-phase cleanup, and an
elemental sulfur cleanup procedure are provided to aid in
elimination of interferences that may be encountered. Other cleanup
procedures may be used if demonstrated to be effective for the
analytes in a wastewater matrix.

3. Contamination and Interferences

    3.1 Solvents, reagents, glassware, and other sample processing
lab ware may yield artifacts, elevated baselines, or matrix
interferences causing misinterpretation of chromatograms. All
materials used in the analysis must be demonstrated free from
contamination and interferences by running blanks initially and with
each extraction batch (samples started through the extraction
process in a given 24-hour period, to a maximum of 20 samples--see
Glossary for detailed definition), as described in section 8.5.
Specific selection of reagents and purification of solvents by
distillation in all-glass systems may be required. Where possible,
labware is cleaned by extraction or solvent rinse, or baking in a
kiln or oven.
    3.2 Glassware must be scrupulously cleaned (Reference 4). Clean
all glassware as soon as possible after use by rinsing with the last
solvent used in it. Solvent rinsing should be followed by detergent
washing with hot water, and rinses with tap water and reagent water.
The glassware should then be drained dry, and heated at 400 [deg]C
for 15-30 minutes. Some thermally stable materials, such as PCBs,
may require higher temperatures and longer baking times for removal.
Solvent rinses with pesticide quality acetone, hexane, or other
solvents may be substituted for heating. Do not heat volumetric
labware above 90 [deg]C. After drying and cooling, store inverted or
capped with solvent-rinsed or baked aluminum foil in a clean
environment to prevent accumulation of dust or other contaminants.
    3.3 Interferences by phthalate esters can pose a major problem
in pesticide analysis when using the electron capture detector. The
phthalate esters generally appear in the chromatogram as large late
eluting peaks, especially in the 15 and 50% fractions from
Florisil[supreg]. Common flexible plastics contain varying amounts
of phthalates that may be extracted or leached from such materials
during laboratory operations. Cross contamination of clean glassware
routinely occurs when plastics are handled during extraction steps,
especially when solvent-wetted surfaces are handled. Interferences
from phthalates can best be minimized by avoiding use of non-
fluoropolymer plastics in the laboratory. Exhaustive cleanup of
reagents and glassware may be required to eliminate background
phthalate contamination (References 5 and 6). Interferences from
phthalate esters can be avoided by using a microcoulometric or
electrolytic conductivity detector.
    3.4 Matrix interferences may be caused by contaminants co-
extracted from the sample. The extent of matrix interferences will
vary considerably from source to source, depending upon the nature
and diversity of the industrial complex or municipality being
sampled. Interferences extracted from

samples high in total organic carbon (TOC) may result in elevated
baselines, or by enhancing or suppressing a signal at or near the
retention time of an analyte of interest. Analyses of the matrix
spike and matrix spike duplicate (Section 8.3) may be useful in
identifying matrix interferences, and the cleanup procedures in
Section 11 may aid in eliminating these interferences. EPA has
provided guidance that may aid in overcoming matrix interferences
(Reference 7); however, unique samples may require additional
cleanup approaches to achieve the MDLs listed in Tables 1 and 2.

4. Safety

    4.1 Hazards associated with each reagent used in this method
have not been precisely defined; however, each chemical compound
should be treated as a potential health hazard. From this viewpoint,
exposure to these chemicals must be reduced to the lowest possible
level by whatever means available. The laboratory is responsible for
maintaining a current awareness file of OSHA regulations regarding
the safe handling of the chemicals specified in this method. A
reference file of safety data sheets (SDSs, OSHA, 29 CFR
1910.12009(g)) should also be made available to all personnel
involved in sample handling and chemical analysis. Additional
references to laboratory safety are available and have been
identified (References 8 and 9) for the information of the analyst.
    4.2 The following analytes covered by this method have been
tentatively classified as known or suspected human or mammalian
carcinogens: 4,4'-DDT, 4,4'-DDD, the BHCs, and the PCBs. Primary
standards of these toxic analytes should be prepared in a chemical
fume hood, and a NIOSH/MESA approved toxic gas respirator should be
worn when high concentrations are handled.
    4.3 This method allows the use of hydrogen as a carrier gas in
place of helium (section 5.8.2). The laboratory should take the
necessary precautions in dealing with hydrogen, and should limit
hydrogen flow at the source to prevent buildup of an explosive
mixture of hydrogen in air.

5. Apparatus and Materials

    Note:  Brand names and suppliers are for illustration purposes
only. No endorsement is implied. Equivalent performance may be
achieved using equipment and materials other than those specified
here. Demonstrating that the equipment and supplies used in the
laboratory achieve the required performance is the responsibility of
the laboratory. Suppliers for equipment and materials in this method
may be found through an on-line search. Please do not contact EPA
for supplier information.

    5.1 Sampling equipment, for discrete or composite sampling.
    5.1.1 Grab sample bottle--Amber glass bottle large enough to
contain the necessary sample volume (nominally 1 L), fitted with a
fluoropolymer-lined screw cap. Foil may be substituted for
fluoropolymer if the sample is not corrosive. If amber bottles are
not available, protect samples from light. Unless pre-cleaned, the
bottle and cap liner must be washed, rinsed with acetone or
methylene chloride, and dried before use to minimize contamination.
    5.1.2 Automatic sampler (optional)--The sampler must use a glass
or fluoropolymer container and tubing for sample collection. If the
sampler uses a peristaltic pump, a minimum length of compressible
silicone rubber tubing may be used. Before use, rinse the
compressible tubing thoroughly with methanol, followed by repeated
rinsing with reagent water to minimize the potential for sample
contamination. An integrating flow meter is required to collect flow
proportional composites. The sample container must be kept
refrigerated at <=6 [deg]C and protected from light during
compositing.
    5.2. Lab ware.
    5.2.1 Extraction.
    <IP_ADDRESS> pH measurement.
    <IP_ADDRESS>.1 pH meter, with combination glass electrode.
    <IP_ADDRESS>.2 pH paper, wide range (Hydrion Papers, or equivalent).
    <IP_ADDRESS> Separatory funnel--Size appropriate to hold the sample
and extraction solvent volumes, equipped with fluoropolymer
stopcock.
    <IP_ADDRESS> Continuous liquid-liquid extractor--Equipped with
fluoropolymer or glass connecting joints and stopcocks requiring no
lubrication. (Hershberg-Wolf Extractor, Ace Glass Company, Vineland,
NJ, or equivalent.)
    <IP_ADDRESS>.1 Round-bottom flask, 500-mL, with heating mantle.
    <IP_ADDRESS>.2 Condenser, Graham, to fit extractor.
    <IP_ADDRESS> Solid-phase extractor--90-mm filter apparatus (Figure 2)
or multi-position manifold.

    Note:  The approved ATP for solid-phase extraction is limited to
disk-based extraction media and associated peripheral equipment.

    <IP_ADDRESS>.1 Vacuum system--Capable of achieving 0.1 bar (25 inch)
Hg (house vacuum, vacuum pump, or water aspirator), equipped with
shutoff valve and vacuum gauge.
    <IP_ADDRESS>.2 Vacuum trap--Made from 500-mL sidearm flask fitted
with single-hole rubber stopper and glass tubing.
    5.2.2 Filtration.
    <IP_ADDRESS> Glass powder funnel, 125- to 250-mL.
    <IP_ADDRESS> Filter paper for above, Whatman 41, or equivalent.
    <IP_ADDRESS> Prefiltering aids--90-mm 1-[mu]m glass fiber filter or
Empore[supreg] Filter Aid 400.
    5.2.3 Drying column.
    <IP_ADDRESS> Chromatographic column--Approximately 400 mm long x 15
mm ID, with fluoropolymer stopcock and coarse frit filter disc
(Kontes or equivalent).
    <IP_ADDRESS> Glass wool--Pyrex, extracted with methylene chloride or
baked at 450 [deg]C for 1 hour minimum.
    5.2.4 Column for Florisil[supreg] or alumina cleanup--
Approximately 300 mm long x 10 mm ID, with fluoropolymer stopcock.
(This column is not required if cartridges containing
Florisil[supreg] are used.)
    5.2.5 Concentration/evaporation.

    Note:  Use of a solvent recovery system with the K-D or other
solvent evaporation apparatus is strongly recommended.

    <IP_ADDRESS> Kuderna-Danish concentrator.
    <IP_ADDRESS>.1 Concentrator tube, Kuderna-Danish--10-mL, graduated
(Kontes or equivalent). Calibration must be checked at the volumes
employed for extract volume measurement. A ground-glass stopper is
used to prevent evaporation of extracts.
    <IP_ADDRESS>.2 Evaporative flask, Kuderna-Danish--500-mL (Kontes or
equivalent). Attach to concentrator tube with connectors.
    <IP_ADDRESS>.3 Snyder column, Kuderna/Danish--Three-ball macro
(Kontes or equivalent).
    <IP_ADDRESS>.4 Snyder column--Two-ball micro (Kontes or equivalent).
    <IP_ADDRESS>.5 Water bath--Heated, with concentric ring cover,
capable of temperature control (2 [deg]C), installed in
a hood using appropriate engineering controls to limit exposure to
solvent vapors.
    <IP_ADDRESS> Nitrogen evaporation device--Equipped with heated bath
that can be maintained at an appropriate temperature for the solvent
and analytes. (N-Evap, Organomation Associates, Inc., or
equivalent).
    <IP_ADDRESS> Rotary evaporator--Buchi/Brinkman-American Scientific or
equivalent, equipped with a variable temperature water bath, vacuum
source with shutoff valve at the evaporator, and vacuum gauge.
    <IP_ADDRESS>.1 A recirculating water pump and chiller are
recommended, as use of tap water for cooling the evaporator wastes
large volumes of water and can lead to inconsistent performance as
water temperatures and pressures vary.
    <IP_ADDRESS>.2 Round-bottom flask--100-mL and 500-mL or larger, with
ground-glass fitting compatible with the rotary evaporator

    Note:  This equipment is used to prepare copper foil or copper
powder for removing sulfur from sample extracts (see Section 6.7.4).

    <IP_ADDRESS> Automated concentrator--Equipped with glassware
sufficient to concentrate 3-400 mL extract to a final volume of 1-10
mL under controlled conditions of temperature and nitrogen flow
(Turbovap, or equivalent). Follow manufacturer's directions and
requirements.
    <IP_ADDRESS> Boiling chips--Glass, silicon carbide, or equivalent,
approximately 10/40 mesh. Heat at 400 [deg]C for 30 minutes, or
solvent rinse or Soxhlet extract with methylene chloride.
    5.2.6 Solid-phase extraction disks--90-mm extraction disks
containing 2 g of 8-[mu]m octadecyl (C18) bonded silica uniformly
enmeshed in a matrix of inert PTFE fibrils (3M Empore[supreg] or
equivalent). The disks should not contain any organic compounds,
either from the PTFE or the bonded silica, which will leach into the
methylene chloride eluant. One liter of reagent water should pass
through the disks in 2-5 minutes, using a vacuum of at least 25
inches of mercury.

    Note:  Extraction disks from other manufacturers may be used in
this procedure, provided that they use the same solid-phase
materials (i.e., octadecyl bonded silica). Disks of other diameters
also may be used, but may adversely affect the flow rate of the
sample through the disk.

    5.3 Vials.

    5.3.1 Extract storage--10- to 15-mL, amber glass, with
fluoropolymer-lined screw cap.
    5.3.2 GC autosampler--1- to 5-mL, amber glass, with
fluoropolymer-lined screw- or crimp-cap, to fit GC autosampler.
    5.4 Balances.
    5.4.1 Analytical--Capable of accurately weighing 0.1 mg.
    5.4.2 Top loading--Capable of weighing 10 mg.
    5.5 Sample cleanup.
    5.5.1 Oven--For baking and storage of adsorbents, capable of
maintaining a constant temperature (5 [deg]C) in the
range of 105-250 [deg]C.
    5.5.2 Muffle furnace--Capable of cleaning glassware or baking
sodium sulfate in the range of 400-450 [deg]C.
    5.5.3 Vacuum system and cartridges for solid-phase cleanup (see
Section 11.2).
    <IP_ADDRESS> Vacuum system--Capable of achieving 0.1 bar (25 in.) Hg
(house vacuum, vacuum pump, or water aspirator), equipped with
shutoff valve and vacuum gauge.
    <IP_ADDRESS> VacElute Manifold (Analytichem International, or
equivalent).
    <IP_ADDRESS> Vacuum trap--Made from 500-mL sidearm flask fitted with
single-hole rubber stopper and glass tubing.
    <IP_ADDRESS> Rack for holding 50-mL volumetric flasks in the
manifold.
    <IP_ADDRESS> Cartridge--Mega Bond Elute, Non-polar, C18 Octadecyl, 10
g/60 mL (Analytichem International or equivalent), used for solid-
phase cleanup of sample extracts (see Section 11.2).
    5.5.4 Sulfur removal tube--40- to 50-mL bottle, test tube, or
Erlenmeyer flask with fluoropolymer-lined screw cap.
    5.6 Centrifuge apparatus.
    5.6.1 Centrifuge--Capable of rotating 500-mL centrifuge bottles
or 15-mL centrifuge tubes at 5,000 rpm minimum.
    5.6.2 Centrifuge bottle--500-mL, with screw cap, to fit
centrifuge.
    5.6.3 Centrifuge tube--15-mL, with screw cap, to fit centrifuge.
    5.7 Miscellaneous lab ware--Graduated cylinders, pipettes,
beakers, volumetric flasks, vials, syringes, and other lab ware
necessary to support the operations in this method.
    5.8 Gas chromatograph--Dual-column with simultaneous split/
splitless, temperature programmable split/splitless (PTV), or on-
column injection; temperature program with isothermal holds, and all
required accessories including syringes, analytical columns, gases,
and detectors. An autosampler is highly recommended because it
injects volumes more reproducibly than manual injection techniques.
Alternatively, two separate single-column gas chromatographic
systems may be employed.
    5.8.1 Example columns and operating conditions.
    <IP_ADDRESS> DB-608 (or equivalent), 30-m long x 0.53-mm ID fused-
silica capillary, 0.83-[mu]m film thickness.
    <IP_ADDRESS> DB-1701 (or equivalent), 30-m long x 0.53-mm ID fused-
silica capillary, 1.0-[mu]m film thickness.
    <IP_ADDRESS> Suggested operating conditions used to meet the
retention times shown in Table 3 are:
    (a) Carrier gas flow rate: Approximately 7 mL/min,
    (b) Initial temperature: 150 [deg]C for 0.5 minute,
    (c) Temperature program: 150-270 [deg]C at 5 [deg]C/min, and
    (d) Final temperature: 270 [deg]C, until trans-Permethrin
elutes.

    Note:  Other columns, internal diameters, film thicknesses, and
operating conditions may be used, provided that the performance
requirements in this method are met. However, the column pair chosen
must have dissimilar phases/chemical properties in order to separate
the compounds of interest in different retention time order. Columns
that only differ in the length, ID, or film thickness, but use the
same stationary phase do not qualify as ``dissimilar.''

    5.8.2 Carrier gas--Helium or hydrogen. Data in the tables in
this method were obtained using helium carrier gas. If hydrogen is
used, analytical conditions may need to be adjusted for optimum
performance, and calibration and all QC tests must be performed with
hydrogen carrier gas. See Section 4.3 for precautions regarding the
use of hydrogen as a carrier gas.
    5.8.3 Detector--Halogen-specific detector (electron capture
detector [ECD], electrolytic conductivity detector [ELCD], or
equivalent). The ECD has proven effective in the analysis of
wastewaters for the analytes listed in Tables 1 and 2, and was used
to develop the method performance data in Section 17 and Tables 4
and 5.
    5.8.4 Data system--A computer system must be interfaced to the
GC that allows continuous acquisition and storage of data from the
detectors throughout the chromatographic program. The computer must
have software that allows searching GC data for specific analytes,
and for plotting responses versus time. Software must also be
available that allows integrating peak areas or peak heights in
selected retention time windows and calculating concentrations of
the analytes.

6. Reagents and Standards

    6.1 pH adjustment.
    6.1.1 Sodium hydroxide solutions.
    <IP_ADDRESS> Concentrated (10 M)--Dissolve 40 g of NaOH (ACS) in
reagent water and dilute to 100 mL.
    <IP_ADDRESS> Dilute (1 M)--Dissolve 40 g NaOH in 1 L of reagent
water.
    6.1.2 Sulfuric acid (1+1)--Slowly add 50 mL of
H2SO4 (ACS, sp. gr. 1.84) to 50 mL of reagent
water.
    6.1.3 Hydrochloric acid--Reagent grade, 6 N.
    6.2 Sodium thiosulfate--(ACS) granular.
    6.3 Sodium sulfate--Sodium sulfate, reagent grade, granular
anhydrous (Baker or equivalent), rinsed with methylene chloride,
baked in a shallow tray at 450 [deg]C for 1 hour minimum, cooled in
a desiccator, and stored in a pre-cleaned glass bottle with screw
cap which prevents moisture from entering. If, after heating, the
sodium sulfate develops a noticeable grayish cast (due to the
presence of carbon in the crystal matrix), that batch of reagent is
not suitable for use and should be discarded. Extraction with
methylene chloride (as opposed to simple rinsing) and baking at a
lower temperature may produce sodium sulfate suitable for use.
    6.4 Reagent water--Reagent water is defined as water in which
the analytes of interest and interfering compounds are not observed
at the MDLs of the analytes in this method.
    6.5 Solvents--Methylene chloride, acetone, methanol, hexane,
acetonitrile, and isooctane, high purity pesticide quality, or
equivalent, demonstrated to be free of the analytes and
interferences (section 3). Purification of solvents by distillation
in all-glass systems may be required.

    Note:  The standards and final sample extracts must be prepared
in the same final solvent.

    6.6 Ethyl ether--Nanograde, redistilled in glass if necessary.
Ethyl ether must be shown to be free of peroxides before use, as
indicated by EM Laboratories Quant test strips (available from
Scientific Products Co. and other suppliers). Procedures recommended
for removal of peroxides are provided with the test strips. After
removal of peroxides, add 20 mL of ethyl alcohol preservative to
each liter of ether.
    6.7 Materials for sample cleanup.
    6.7.1 Florisil[supreg]--PR grade (60/100 mesh), activated at
650-700 [deg]C, stored in the dark in a glass container with
fluoropolymer-lined screw cap. Activate each batch immediately prior
to use for 16 hours minimum at 130 [deg]C in a foil-covered glass
container and allow to cool. Alternatively, 500 mg cartridges (J.T.
Baker, or equivalent) may be used.
    <IP_ADDRESS> Cartridge certification--Each cartridge lot must be
certified to ensure recovery of the analytes of interest and removal
of 2,4,6-trichlorophenol. To make the test mixture, add the
trichlorophenol solution (section <IP_ADDRESS>) to the same standard used
to prepare the Quality Control Check Sample (section 6.8.3).
Transfer the mixture to the column and dry the column. Pre-elute
with three 10-mL portions of elution solvent, drying the column
between elutions. Elute the cartridge with 10 mL each of methanol
and water, as in section <IP_ADDRESS>.
    <IP_ADDRESS> Concentrate the eluant to per section 10.3.3, exchange
to isooctane or hexane per section 10.3.3, and inject 1.0 [mu]L of
the concentrated eluant into the GC using the procedure in section
12. The recovery of all analytes (including the unresolved GC peaks)
shall be within the ranges for calibration verification (section
13.6 and Table 4), the recovery of trichlorophenol shall be less
than 5%, and no peaks interfering with the target analytes shall be
detected. Otherwise the Florisil cartridge is not performing
properly and the cartridge lot shall be rejected.
    <IP_ADDRESS> Florisil cartridge calibration solution--2,4,6-
Trichlorophenol, 0.1 [mu]g/mL in acetone.
    6.7.2 SPE elution solvent--Methylene
chloride:acetonitrile:hexane (50:3:47).
    6.7.3 Alumina, neutral, Brockman Activity I, 80-200 mesh (Fisher
Scientific certified, or equivalent). Heat in a glass bottle for 16
hours at 400 to 450 [deg]C. Seal and cool to room temperature. Add
7% (w/w) reagent water and mix for 10 to 12 hours. Keep bottle
tightly sealed.

    6.7.4 Sulfur removal.
    <IP_ADDRESS> Copper foil or powder--Fisher, Alfa Aesar, or
equivalent. Cut copper foil into approximately 1-cm squares. Copper
must be activated before it may be used, as described below.
    <IP_ADDRESS>.1 Place the quantity of copper needed for sulfur removal
(section <IP_ADDRESS>) in a ground-glass-stoppered Erlenmeyer flask or
bottle. Cover the foil or powder with methanol.
    <IP_ADDRESS>.2 Add HCl dropwise (0.5-1.0 mL) while swirling, until
the copper brightens.
    <IP_ADDRESS>.3 Pour off the methanol/HCl and rinse 3 times with
reagent water to remove all traces of acid, then 3 times with
acetone, then 3 times with hexane.
    <IP_ADDRESS>.4 For copper foil, cover with hexane after the final
rinse. Store in a stoppered flask under nitrogen until used. For the
powder, dry on a rotary evaporator. Store in a stoppered flask under
nitrogen until used. Inspect the copper foil or powder before each
use. It must have a bright, non-oxidized appearance to be effective.
Copper foil or powder that has oxidized may be reactivated using the
procedure described above.
    <IP_ADDRESS> Tetrabutylammonium sulfite (TBA sulfite)--Prepare as
described below.
    <IP_ADDRESS>.1 Tetrabutylammonium hydrogen sulfate,
[CH3(CH2)3]4NHSO4.

    <IP_ADDRESS>.2 Sodium sulfite, Na2SO3.
    <IP_ADDRESS>.3 Dissolve approximately 3 g tetrabutylammonium hydrogen
sulfate in 100 mL of reagent water in an amber bottle with
fluoropolymer-lined screw cap. Extract with three 20-mL portions of
hexane and discard the hexane extracts.
    <IP_ADDRESS>.4 Add 25 g sodium sulfite to produce a saturated
solution. Store at room temperature. Replace after 1 month.
    6.7.5 Sodium chloride--Reagent grade, prepare at 5% (w/v)
solution in reagent water.
    6.8 Stock standard solutions--Stock standard solutions may be
prepared from pure materials, or purchased as certified solutions.
Traceability must be to the National Institute of Standards and
Technology (NIST) or other national or international standard, when
available. Stock solution concentrations alternative to those below
may be used. Because of the toxicity of some of the compounds,
primary dilutions should be prepared in a hood, and a NIOSH/MESA
approved toxic gas respirator should be worn when high
concentrations of neat materials are handled. The following
procedure may be used to prepare standards from neat materials.
    6.8.1 Accurately weigh about 0.0100 g of pure material in a 10-
mL volumetric flask. Dilute to volume in pesticide quality hexane,
isooctane, or other suitable solvent. Larger volumes may be used at
the convenience of the laboratory. When compound purity is assayed
to be 96% or greater, the weight may be used without correction to
calculate the concentration of the stock standard. Commercially
prepared stock standards may be used at any concentration if they
are certified by the manufacturer or by an independent source.
    <IP_ADDRESS> Unless stated otherwise in this method, store non-
aqueous standards in fluoropolymer-lined screw-cap, or heat-sealed,
glass containers, in the dark at -20 to -10 [deg]C. Store aqueous
standards; e.g., the aqueous LCS (section 8.4), in the dark at <=6
[deg]C, but do not freeze.
    <IP_ADDRESS> Standards prepared by the laboratory may be stored for
up to one year, except when comparison with QC check standards
indicates that a standard has degraded or become more concentrated
due to evaporation, or unless the laboratory has data on file to
prove stability for a longer period. Commercially prepared standards
may be stored until the expiration date provided by the vendor,
except when comparison with QC check standards indicates that a
standard has degraded or become more concentrated due to
evaporation, or unless the laboratory has data from the vendor on
file to prove stability for a longer period.
    6.8.2 Calibration solutions--It is necessary to prepare
calibration solutions for the analytes of interest (section 1.4)
only using an appropriate solvent (isooctane or hexane may be used).
Whatever solvent is used, both the calibration standards and the
final sample extracts must use the same solvent. Other analytes may
be included as desired.
    <IP_ADDRESS> Prepare calibration standards for the single-component
analytes of interest and surrogates at a minimum of three
concentration levels (five are suggested) by adding appropriate
volumes of one or more stock standards to volumetric flasks. One of
the calibration standards should be at a concentration at or below
the ML specified in Table 1, or 2, or as specified by a regulatory/
control authority or in a permit. The ML value may be rounded to a
whole number that is more convenient for preparing the standard, but
must not exceed the ML value listed in Tables 1 or 2 for those
analytes which list ML values. Alternatively, the laboratory may
establish an ML for each analyte based on the concentration of the
lowest calibration standard in a series of standards produced by the
laboratory or obtained from a commercial vendor, again, provided
that the ML does not exceed the ML in Table 1 and 2, and provided
that the resulting calibration meets the acceptance criteria in
section 7.5.2 based on the RSD, RSE, or R\2\.
    (a) The other concentrations should correspond to the expected
range of concentrations found in real samples or should define the
working range of the GC system. A minimum of six concentration
levels is required for a second order, non-linear (e.g., quadratic;
ax\2\ + bx + c = 0) calibration (section 7.5.2 or 7.6.2).
Calibrations higher than second order are not allowed. A separate
standard near the MDL may be analyzed as a check on sensitivity, but
should not be included in the linearity assessment. The solvent for
the standards must match the final solvent for the sample extracts
(e.g., isooctane or hexane).

    Note: The option for non-linear calibration may be necessary to
address specific instrumental techniques. However, it is not EPA's
intent to allow non-linear calibration to be used to compensate for
detector saturation or to avoid proper instrument maintenance.

    (b) Given the number of analytes included in this method, it is
highly likely that some will coelute on one or both of the GC
columns used for the analysis. Divide the analytes into two or more
groups and prepare separate calibration standards for each group, at
multiple concentrations (e.g., a five-point calibration will require
ten solutions to cover two groups of analytes). Table 7 provides
information on dividing the target analytes into separate
calibration mixtures that should minimize or eliminate co-elutions.
This table is provided solely as guidance, based on the GC columns
suggested in this method. If an analyte listed in Table 7 is not an
analyte of interest in a given laboratory setting, then it need not
be included in a calibration mixture.

    Note:  Many commercially available standards are divided into
separate mixtures to address this issue.

    (c) If co-elutions occur in analysis of a sample, a co-elution
on one column is acceptable so long as effective separation of the
co-eluting compounds can be achieved on the second column.
    <IP_ADDRESS> Multi-component analytes (e.g., PCBs as Aroclors, and
Toxaphene).
    <IP_ADDRESS>.1 A standard containing a mixture of Aroclor 1016 and
Aroclor 1260 will include many of the peaks represented in the other
Aroclor mixtures. As a result, a multi-point initial calibration
employing a mixture of Aroclors 1016 and 1260 at three to five
concentrations should be sufficient to demonstrate the linearity of
the detector response without the necessity of performing multi-
point initial calibrations for each of the seven Aroclors. In
addition, such a mixture can be used as a standard to demonstrate
that a sample does not contain peaks that represent any one of the
Aroclors. This standard can also be used to determine the
concentrations of either Aroclor 1016 or Aroclor 1260, should they
be present in a sample. Therefore, prepare a minimum of three
calibration standards containing equal concentrations of both
Aroclor 1016 and Aroclor 1260 by dilution of the stock standard with
isooctane or hexane. The concentrations should correspond to the
expected range of concentrations found in real samples and should
bracket the linear range of the detector.
    <IP_ADDRESS>.2 Single standards of each of the other five Aroclors
are required to aid the analyst in pattern recognition. Assuming
that the Aroclor 1016/1260 standards described in Section <IP_ADDRESS>.1
have been used to demonstrate the linearity of the detector, these
single standards of the remaining five Aroclors also may be used to
determine the calibration factor for each Aroclor. Prepare a
standard for each of the other Aroclors. The concentrations should
generally correspond to the mid-point of the linear range of the
detector, but lower concentrations may be employed at the discretion
of the analyst based on project requirements.
    <IP_ADDRESS>.3 For Toxaphene, prepare a minimum of three calibration
standards containing Toxaphene by dilution of the stock standard
with isooctane or hexane. The concentrations should correspond to
the expected range of concentrations found in

real samples and should bracket the linear range of the detector.
    6.8.3 Quality Control (QC) Check Sample Concentrate--Prepare one
or more mid-level standard mixtures (concentrates) in acetone (or
other water miscible solvent). The concentrate is used as the
spiking solution with which to prepare the Demonstration of
Capabilities (DOC) samples, the Laboratory Control Sample (LCS), and
Matrix Spike (MS) and Matrix Spike Duplicate (MSD) samples described
in section 8. If prepared by the laboratory (as opposed the
purchasing it from a commercial supplier), the concentrate must be
prepared independently from the standards used for calibration, but
may be prepared from the same source as the second-source standard
used for calibration verification (section 7.7). Regardless of the
source, the concentrate must be in a water-miscible solvent, as
noted above. The concentrate is used to prepare the DOC and LCS
(sections 8.2.1 and 8.4) and MS/MSD samples (section 8.3). Depending
on the analytes of interest for a given sample (see Section 1.4),
multiple solutions and multiple LCS or MS/MSD samples may be
required to account for co-eluting analytes. However, a co-elution
on one column is acceptable so long as effective separation of the
co-eluting compounds can be achieved on the second column. In
addition, the concentrations of the MS/MSD samples should reflect
any relevant compliance limits for the analytes of interest, as
described in section 8.3.1. If a custom spiking solution is required
for a specific discharge (section 8.3.1), prepare it separately from
the DOC and LCS solution.

    Note:  Some commercially available standards are divided into
separate mixtures to address the co-elution issue.

    6.8.4 Calibration Verification Standards--In order to verify the
results of the initial calibration standards, prepare one or more
mid-level standard mixtures in isooctane or hexane, using standards
obtained from a second source (different manufacturer or different
certified lot from the calibration standards). These standards will
be analyzed to verify the accuracy of the calibration (sections 7.7
and 13.6.2). As with the QC sample concentrate in section 6.8.3,
multiple solutions may be required to address co-elutions among all
of the analytes.
    6.8.5 Internal standard solution--If the internal standard
calibration technique is to be used, prepare pentachloronitrobenzene
(PCNB) at a concentration of 10 [mu]g/mL in ethyl acetate.
Alternative and multiple internal standards; e.g., tetrachloro-m-
xylene, 4,4'-dibromobiphenyl, and/or decachlorobiphenyl may be used
provided that the laboratory performs all QC tests and meets all QC
acceptance criteria with the alternative or additional internal
standard(s) as an integral part of this method.
    6.8.6 Surrogate solution--Prepare a solution containing one or
more surrogates at a concentration of 2 [mu]g/mL in acetone.
Potential surrogates include: dibutyl chlorendate (DBC),
tetrachloro-m-xylene (TCMX), 4,4'-dibromobiphenyl, or
decachlorobiphenyl. Alternative surrogates and concentrations may be
used, provided the laboratory performs all QC tests and meets all QC
acceptance criteria with the alternative surrogate(s) as an integral
part of this method. If the internal standard calibration technique
is used, do not use the internal standard as a surrogate.
    6.8.7 DDT and endrin decomposition (breakdown) solution--Prepare
a solution containing endrin at a concentration of 50 ng/mL and
4,4'-DDT at a concentration of 100 ng/mL, in isooctane or hexane. A
1-[micro]L injection of this standard will contain 50 picograms (pg)
of endrin and 100 pg of DDT. The concentration of the solution may
be adjusted by the laboratory to accommodate other injection volumes
such that the same masses of the two analytes are introduced into
the instrument.

7. Calibration

    7.1 Establish gas chromatographic operating conditions
equivalent to those in Section 5.8.1 and Footnote 2 to Table 3.
Alternative temperature program and flow rate conditions may be
used. The system may be calibrated using the external standard
technique (section 7.5) or the internal standard technique (section
7.6). It is necessary to calibrate the system for the analytes of
interest (section 1.4) only.
    7.2 Separately inject the mid-level calibration standard for
each calibration mixture. Store the retention time on each GC
column.
    7.3 Injection of calibration solutions--Inject a constant volume
in the range of 0.5 to 2.0 [mu]L of each calibration solution into
the GC column/detector pairs. An alternative volume (see Section
12.3) may be used provided all requirements in this method are met.
Beginning with the lowest level mixture and proceeding to the
highest level mixture may limit the risk of carryover from one
standard to the next, but other sequences may be used. An instrument
blank should be analyzed after the highest standard to demonstrate
that there is no carry-over within the system for this calibration
range.
    7.4 For each analyte, compute, record, and store, as a function
of the concentration injected, the retention time and peak area on
each column/detector system. If multi-component analytes are to be
analyzed, store the retention time and peak area for the three to
five exclusive (unique large) peaks for each PCB or technical
chlordane. Use four to six peaks for toxaphene.
    7.5 External standard calibration.
    7.5.1 From the calibration data (Section 7.4), calculate the
calibration factor (CF) for each analyte at each concentration
according to the following equation:
[GRAPHIC] [TIFF OMITTED] TR28AU17.000

Where:

Cs = Concentration of the analyte in the standard (ng/mL)
As = Peak height or area

    For multi-component analytes, choose a series of characteristic
peaks for each analyte (3 to 5 for each Aroclor, 4 to 6 for
toxaphene) and calculate individual calibration factors for each
peak. Alternatively, for toxaphene, sum the areas of all of the
peaks in the standard chromatogram and use the summed area to
determine the calibration factor. (If this alternative is used, the
same approach must be used to quantitate the analyte in the
samples.)
    7.5.2 Calculate the mean (average) and relative standard
deviation (RSD) of the calibration factors. If the RSD is less than
20%, linearity through the origin can be assumed and the average CF
can be used for calculations. Alternatively, the results can be used
to fit a linear or quadratic regression of response, As,
vs. concentration Cs. If used, the regression must be
weighted inversely proportional to concentration. The coefficient of
determination (R\2\) of the weighted regression must be greater than
0.920. Alternatively, the relative standard error (Reference 10) may
be used as an acceptance criterion. As with the RSD, the RSE must be
less than 20%. If an RSE less than 20% cannot be achieved for a
quadratic regression, system performance is unacceptable and the
system must be adjusted and re-calibrated.

    Note: Regression calculations are not included in this method
because the calculations are cumbersome and because many GC/ECD data
systems allow selection of weighted regression for calibration and
calculation of analyte concentrations.

    7.6 Internal standard calibration.
    7.6.1 From the calibration data (Section 7.4), calculate the
response factor (RF) for each analyte at each concentration
according to the following equation:
[GRAPHIC] [TIFF OMITTED] TR28AU17.001

Where:

As = Response for the analyte to be measured.
Ais = Response for the internal standard.
Cis = Concentration of the internal standard (ng/mL)
Cs = Concentration of the analyte to be measured (ng/mL).

    7.6.2 Calculate the mean (average) and relative standard
deviation (RSD) of the response factors. If the RSD is less than
15%, linearity through the origin can be assumed and the average RF
can be used for calculations. Alternatively, the results can be used
to prepare a calibration curve of response ratios, As/
Ais, vs. concentration ratios, Cs/
Cis, for the analyte. A minimum of six concentration
levels is required for a non-linear (e.g., quadratic) regression. If
used, the regression must be weighted inversely proportional to
concentration, and the coefficient of determination of the weighted
regression must be greater than 0.920. Alternatively, the relative
standard error (Reference 10) may be used as an acceptance
criterion. As with the RSD, the RSE must be less than 15%. If an RSE
less than 15% cannot be achieved for a quadratic regression, system
performance is unacceptable and the system must be adjusted and re-
calibrated.
    7.7 The working calibration curve, CF, or RF must be verified
immediately after calibration and at the beginning and end of each
24-hour shift by the analysis of a mid-level calibration standard.
The calibration verification standard(s) must be obtained from a
second manufacturer or a manufacturer's batch prepared

independently from the batch used for calibration (Section 6.8.4).
Requirements for calibration verification are given in Section 13.6
and Table 4. Alternatively, calibration verification may be
performed after a set number of injections (e.g., every 20
injections), to include injection of extracts of field samples, QC
samples, instrument blanks, etc. (i.e., it is based on the number of
injections performed, not sample extracts). The time for the
injections may not exceed 24 hours.

    Note: The 24-hour shift begins after analysis of the combined QC
standard (calibration verification) and ends 24 hours later. The
ending calibration verification standard is run immediately after
the last sample run during the 24-hour shift, so the beginning and
ending calibration verifications are outside of the 24-hour shift.
If calibration verification is based on the number of injections
instead of time, then the ending verification standard for one group
of injections may be used as the beginning verification for the next
group of injections.

    7.8 Florisil[supreg] calibration--The column cleanup procedure
in Section 11.3 utilizes Florisil column chromatography.
Florisil[supreg] from different batches or sources may vary in
adsorptive capacity. To standardize the amount of Florisil[supreg]
which is used, use of the lauric acid value (Reference 11) is
suggested. The referenced procedure determines the adsorption from a
hexane solution of lauric acid (mg) per g of Florisil[supreg]. The
amount of Florisil[supreg] to be used for each column is calculated
by dividing 110 by this ratio and multiplying by 20 g. If cartridges
containing Florisil[supreg] are used, then this step is not
necessary.

8. Quality Control

    8.1 Each laboratory that uses this method is required to operate
a formal quality assurance program. The minimum requirements of this
program consist of an initial demonstration of laboratory capability
and ongoing analysis of spiked samples and blanks to evaluate and
document data quality. The laboratory must maintain records to
document the quality of data generated. Ongoing data quality checks
are compared with established performance criteria to determine if
the results of analyses meet performance requirements of this
method. A quality control check standard (LCS, section 8.4) must be
prepared and analyzed with each batch of samples to confirm that the
measurements were performed in an in-control mode of operation. A
laboratory may develop its own performance criteria (as QC
acceptance criteria), provided such criteria are as or more
restrictive than the criteria in this method.
    8.1.1 The laboratory must make an initial demonstration of the
capability (IDC) to generate acceptable precision and recovery with
this method. This demonstration is detailed in Section 8.2. On a
continuing basis, the laboratory must repeat demonstration of
capability (DOC) at least annually.
    8.1.2 In recognition of advances that are occurring in
analytical technology, and to overcome matrix interferences, the
laboratory is permitted certain options (section 1.8 and 40 CFR
136.6(b) [Reference 12]) to improve separations or lower the costs
of measurements. These options may include alternative extraction
(e.g., other solid-phase extraction materials and formats),
concentration, and cleanup procedures, and changes in GC columns
(Reference 12). Alternative determinative techniques, such as the
substitution of spectroscopic or immunoassay techniques, and changes
that degrade method performance, are not allowed. If an analytical
technique other than the techniques specified in this method is
used, that technique must have a specificity equal to or greater
than the specificity of the techniques in this method for the
analytes of interest. The laboratory is also encouraged to
participate in performance evaluation studies (see section 8.8).
    <IP_ADDRESS> Each time a modification listed above is made to this
method, the laboratory is required to repeat the procedure in
section 8.2. If the detection limit of the method will be affected
by the change, the laboratory is required to demonstrate that the
MDLs (40 CFR part 136, appendix B) are lower than one-third the
regulatory compliance limit or as low as the MDLs in this method,
whichever are greater. If calibration will be affected by the
change, the instrument must be recalibrated per section 7. Once the
modification is demonstrated to produce results equivalent or
superior to results produced by this method as written, that
modification may be used routinely thereafter, so long as the other
requirements in this method are met (e.g., matrix spike/matrix spike
duplicate recovery and relative percent difference).
    <IP_ADDRESS>.1 If an allowed method modification, is to be applied to
a specific discharge, the laboratory must prepare and analyze matrix
spike/matrix spike duplicate (MS/MSD) samples (section 8.3) and LCS
samples (section 8.4). The laboratory must include surrogates
(Section 8.7) in each of the samples. The MS/MSD and LCS samples
must be fortified with the analytes of interest (section 1.4). If
the modification is for nationwide use, MS/MSD samples must be
prepared from a minimum of nine different discharges (See section
<IP_ADDRESS>.2), and all QC acceptance criteria in this method must be
met. This evaluation only needs to be performed once other than for
the routine QC required by this method (for example it could be
performed by the vendor of an alternative material) but any
laboratory using that specific material must have the results of the
study available. This includes a full data package with the raw data
that will allow an independent reviewer to verify each determination
and calculation performed by the laboratory (see section <IP_ADDRESS>.5,
items (a)-(q)).
    <IP_ADDRESS>.2 Sample matrices on which MS/MSD tests must be
performed for nationwide use of an allowed modification:
    (a) Effluent from a publicly owned treatment works (POTW).
    (b) ASTM D5905 Standard Specification for Substitute Wastewater.
    (c) Sewage sludge, if sewage sludge will be in the permit.
    (d) ASTM D1141 Standard Specification for Substitute Ocean
Water, if ocean water will be in the permit.
    (e) Untreated and treated wastewaters up to a total of nine
matrix types (see https://www.epa.gov/eg/industrial-effluent-guidelines for a list of industrial categories with existing
effluent guidelines).
    (i) At least one of the above wastewater matrix types must have
at least one of the following characteristics:
    (A) Total suspended solids greater than 40 mg/L.
    (B) Total dissolved solids greater than 100 mg/L.
    (C) Oil and grease greater than 20 mg/L.
    (D) NaCl greater than 120 mg/L.
    (E) CaCO3 greater than 140 mg/L.
    (ii) The interim acceptance criteria for MS, MSD recoveries that
do not have recovery limits in Table 4 or developed in section
8.3.3, and for surrogates that do not have recovery limits developed
in section 8.6, must be no wider than 60-140%, and the relative
percent difference (RPD) of the concentrations in the MS and MSD
that do not have RPD limits in Table 4 or developed in section
8.3.3, must be less than 30%. Alternatively, the laboratory may use
the laboratory's in-house limits if they are tighter.
    (f) A proficiency testing (PT) sample from a recognized
provider, in addition to tests of the nine matrices (section
<IP_ADDRESS>.1).
    <IP_ADDRESS> The laboratory must maintain records of modifications
made to this method. These records include the following, at a
minimum:
    <IP_ADDRESS>.1 The names, titles, and business street addresses,
telephone numbers, and email addresses, of the analyst(s) that
performed the analyses and modification, and of the quality control
officer that witnessed and will verify the analyses and
modifications.
    <IP_ADDRESS>.2 A list of analytes, by name and CAS Registry number.
    <IP_ADDRESS>.3 A narrative stating reason(s) for the modifications.
    <IP_ADDRESS>.4 Results from all quality control (QC) tests comparing
the modified method to this method, including:
    (a) Calibration (section 7).
    (b) Calibration verification (section 13.6).
    (c) Initial demonstration of capability (section 8.2).
    (d) Analysis of blanks (section 8.5).
    (e) Matrix spike/matrix spike duplicate analysis (section 8.3).
    (f) Laboratory control sample analysis (section 8.4).
    <IP_ADDRESS>.5 Data that will allow an independent reviewer to
validate each determination by tracing the instrument output (peak
height, area, or other signal) to the final result. These data are
to include:
    (a) Sample numbers and other identifiers.
    (b) Extraction dates.
    (c) Analysis dates and times.
    (d) Analysis sequence/run chronology.
    (e) Sample weight or volume (section 10).
    (f) Extract volume prior to each cleanup step (sections 10 and
11).
    (g) Extract volume after each cleanup step (section 11).
    (h) Final extract volume prior to injection (sections 10 and
12).

    (i) Injection volume (sections 12.3 and 13.2).
    (j) Sample or extract dilution (section 15.4).
    (k) Instrument and operating conditions.
    (l) Column (dimensions, material, etc.).
    (m) Operating conditions (temperatures, flow rates, etc.).
    (n) Detector (type, operating conditions, etc.).
    (o) Chromatograms and other recordings of raw data.
    (p) Quantitation reports, data system outputs, and other data to
link the raw data to the results reported.
    (q) A written Standard Operating Procedure (SOP).
    <IP_ADDRESS>.6 Each individual laboratory wishing to use a given
modification must perform the start-up tests in section 8.1.2 (e.g.,
DOC, MDL), with the modification as an integral part of this method
prior to applying the modification to specific discharges. Results
of the DOC must meet the QC acceptance criteria in Table 5 for the
analytes of interest (section 1.4), and the MDLs must be equal to or
lower than the MDLs in Tables 1 and 2 for the analytes of interest.
    8.1.3 Before analyzing samples, the laboratory must analyze a
blank to demonstrate that interferences from the analytical system,
lab ware, and reagents, are under control. Each time a batch of
samples is extracted or reagents are changed, a blank must be
extracted and analyzed as a safeguard against laboratory
contamination. Requirements for the blank are given in section 8.5.
    8.1.4 The laboratory must, on an ongoing basis, spike and
analyze samples to monitor and evaluate method and laboratory
performance on the sample matrix. The procedure for spiking and
analysis is given in section 8.3.
    8.1.5 The laboratory must, on an ongoing basis, demonstrate
through analysis of a quality control check sample (laboratory
control sample, LCS; on-going precision and recovery sample, OPR)
that the measurement system is in control. This procedure is
described in Section 8.4.
    8.1.6 The laboratory should maintain performance records to
document the quality of data that is generated. This procedure is
given in section 8.7.
    8.1.7 The large number of analytes tested in performance tests
in this method present a substantial probability that one or more
will fail acceptance criteria when all analytes are tested
simultaneously, and a re-test (reanalysis) is allowed if this
situation should occur. If, however, continued re-testing results in
further repeated failures, the laboratory should document the
failures and either avoid reporting results for the analytes that
failed or report the problem and failures with the data. A QC
failure does not relieve a discharger or permittee of reporting
timely results.
    8.2 Demonstration of capability (DOC)--To establish the ability
to generate acceptable recovery and precision, the laboratory must
perform the DOC in sections 8.2.1 through 8.2.6 for the analytes of
interest initially and in an on-going manner at least annually. The
laboratory must also establish MDLs for the analytes of interest
using the MDL procedure at 40 CFR part 136, appendix B. The
laboratory's MDLs must be equal to or lower than those listed in
Tables 1 or 2, or lower than one-third the regulatory compliance
limit, whichever is greater. For MDLs not listed in Tables 1 or 2,
the laboratory must determine the MDLs using the MDL procedure at 40
CFR part 136, appendix B under the same conditions used to determine
the MDLs for the analytes listed in Tables 1 and 2. When analyzing
the PCBs as Aroclors, it is only necessary to establish an MDL for
one of the multi-component analytes (e.g., PCB 1254), or the mixture
of Aroclors 1016 and 1260 may be used to establish MDLs for all of
the Aroclors. Similarly, MDLs for other multi-component analytes
(e.g., Chlordanes) may be determined using only one of the major
components. All procedures used in the analysis, including cleanup
procedures, must be included in the DOC.
    8.2.1 For the DOC, a QC check sample concentrate containing each
analyte of interest (section 1.4) is prepared in a water-miscible
solvent using the solution in section 6.8.3.

    Note: QC check sample concentrates are no longer available from
EPA.

    8.2.2 Using a pipet or syringe, prepare four QC check samples by
adding an appropriate volume of the concentrate and of the
surrogate(s) to each of four 1-L aliquots of reagent water. Swirl or
stir to mix.
    8.2.3 Extract and analyze the well-mixed QC check samples
according to the method beginning in section 10.
    8.2.4 Calculate the average percent recovery (X) and the
standard deviation (s) of the percent recovery for each analyte
using the four results.
    8.2.5 For each analyte, compare s and X with the corresponding
acceptance criteria for precision and recovery in Table 4. For
analytes in Table 2 that are not listed in Table 4, QC acceptance
criteria must be developed by the laboratory. EPA has provided
guidance for development of QC acceptance criteria (References 12
and 13). If s and X for all analytes of interest meet the acceptance
criteria, system performance is acceptable and analysis of blanks
and samples can begin. If any individual s exceeds the precision
limit or any individual X falls outside the range for recovery,
system performance is unacceptable for that analyte.

    Note:  The large number of analytes in Tables 1 and 2 present a
substantial probability that one or more will fail at least one of
the acceptance criteria when many or all analytes are determined
simultaneously.

    8.2.6 When one or more of the analytes tested fail at least one
of the acceptance criteria, repeat the test for only the analytes
that failed. If results for these analytes pass, system performance
is acceptable and analysis of samples and blanks may proceed. If one
or more of the analytes again fail, system performance is
unacceptable for the analytes that failed the acceptance criteria.
Correct the problem and repeat the test (section 8.2). See section
8.1.7 for disposition of repeated failures.

    Note: To maintain the validity of the test and re-test, system
maintenance and/or adjustment is not permitted between this pair of
tests.

    8.3 Matrix spike and matrix spike duplicate (MS/MSD)--The
purpose of the MS/MSD requirement is to provide data that
demonstrate the effectiveness of the method as applied to the
samples in question by a given laboratory, and both the data user
(discharger, permittee, regulated entity, regulatory/control
authority, customer, other) and the laboratory share responsibility
for provision of such data. The data user should identify the sample
and the analytes of interest (section 1.4) to be spiked and provide
sufficient sample volume to perform MS/MSD analyses. The laboratory
must, on an ongoing basis, spike at least 5% of the samples in
duplicate from each discharge being monitored to assess accuracy
(recovery and precision). If direction cannot be obtained from the
data user, the laboratory must spike at least one sample in
duplicate per extraction batch of up to 20 samples with the analytes
in Table 1. Spiked sample results should be reported only to the
data user whose sample was spiked, or as requested or required by a
regulatory/control authority, or in a permit.
    8.3.1. If, as in compliance monitoring, the concentration of a
specific analyte will be checked against a regulatory concentration
limit, the concentration of the spike should be at that limit;
otherwise, the concentration of the spike should be one to five
times higher than the background concentration determined in section
8.3.2, at or near the midpoint of the calibration range, or at the
concentration in the LCS (section 8.4) whichever concentration would
be larger. When no information is available, the mid-point of the
calibration may be used.
    8.3.2 Analyze one sample aliquot to determine the background
concentration (B) of the each analyte of interest. If necessary to
meet the requirement in section 8.3.1, prepare a new check sample
concentrate (section 8.2.1) appropriate for the background
concentration. Spike and analyze two additional sample aliquots of
the same volume as the original sample, and determine the
concentrations after spiking (A1 and A2) of
each analyte. Calculate the percent recoveries (P1 and
P2) as:
[GRAPHIC] [TIFF OMITTED] TR28AU17.002

where T is the known true value of the spike.

    Also calculate the relative percent difference (RPD) between the
concentrations (A1 and A2):
[GRAPHIC] [TIFF OMITTED] TR28AU17.003

    8.3.3 Compare the percent recoveries (P1 and
P2) and the RPD for each analyte in the MS/MSD aliquots
with the corresponding QC acceptance criteria for recovery (P) and
RPD in Table 4.
    (a) If any individual P falls outside the designated range for
recovery in either aliquot, or the RPD limit is exceeded, the result
for the analyte in the unspiked sample is suspect and may not be
reported or used

for permitting or regulatory compliance. See section 8.1.7 for
disposition of failures.
    (b) For analytes in Table 2 not listed in Table 4, QC acceptance
criteria must be developed by the laboratory. EPA has provided
guidance for development of QC acceptance criteria (References 12
and 13).
    8.3.4 After analysis of a minimum of 20 MS/MSD samples for each
target analyte and surrogate, and if the laboratory chooses to
develop and apply optional in-house QC limits, the laboratory should
calculate and apply the optional in-house QC limits for recovery and
RPD of future MS/MSD samples (Section 8.3). The optional in-house QC
limits for recovery are calculated as the mean observed recovery
3 standard deviations, and the upper QC limit for RPD is
calculated as the mean RPD plus 3 standard deviations of the RPDs.
The in-house QC limits must be updated at least every two years and
re-established after any major change in the analytical
instrumentation or process. At least 80% of the analytes tested in
the MS/MSD must have in-house QC acceptance criteria that are
tighter than those in Table 4 and the remaining analytes (those not
included in the 80%) must meet the acceptance criteria in Table 4.
If an in-house QC limit for the RPD is greater than the limit in
Table 4, then the limit in Table 4 must be used. Similarly, if an
in-house lower limit for recovery is below the lower limit in Table
4, then the lower limit in Table 4 must be used, and if an in-house
upper limit for recovery is above the upper limit in Table 4, then
the upper limit in Table 4 must be used. The laboratory must
evaluate surrogate recovery data in each sample against its in-house
surrogate recovery limits. The laboratory may use 60 -140% as
interim acceptance criteria for surrogate recoveries until in-house
limits are developed. Alternatively, surrogate recovery limits may
be developed from laboratory control charts. In-house QC acceptance
criteria must be updated at least every two years.
    8.4 Laboratory control sample (LCS)--A QC check sample
(laboratory control sample, LCS; on-going precision and recovery
sample, OPR) containing each single-component analyte of interest
(section 1.4) must be extracted, concentrated, and analyzed with
each extraction batch of up to 20 samples (section 3.1) to
demonstrate acceptable recovery of the analytes of interest from a
clean sample matrix. If multi-peak analytes are required, extract
and prepare at least one as an LCS for each batch. Alternatively,
the laboratory may set up a program where multi-peak LCS is rotated
with a single-peak LCS.
    8.4.1 Prepare the LCS by adding QC check sample concentrate
(sections 6.8.3 and 8.2.1) to reagent water. Include all analytes of
interest (section 1.4) in the LCS. The volume of reagent water must
be the same as the nominal volume used for the sample, the DOC
(Section 8.2), the blank (section 8.5), and the MS/MSD (section
8.3). Also add a volume of the surrogate solution (section 6.8.6).
    8.4.2 Analyze the LCS prior to analysis of samples in the
extraction batch (Section 3.1). Determine the concentration (A) of
each analyte. Calculate the percent recovery as:
[GRAPHIC] [TIFF OMITTED] TR28AU17.004

where T is the true value of the concentration in the LCS.

    8.4.3 For each analyte, compare the percent recovery (P) with
its corresponding QC acceptance criterion in Table 4. For analytes
of interest in Table 2 not listed in Table 4, use the QC acceptance
criteria developed for the MS/MSD (section <IP_ADDRESS>), or limits based
on laboratory control charts. If the recoveries for all analytes of
interest fall within the designated ranges, analysis of blanks and
field samples may proceed. If any individual recovery falls outside
the range, proceed according to section 8.4.4.

    Note:  The large number of analytes in Tables 1 and 2 present a
substantial probability that one or more will fail the acceptance
criteria when all analytes are tested simultaneously. Because a re-
test is allowed in event of failure (sections 8.1.7 and 8.4.4), it
may be prudent to extract and analyze two LCSs together and evaluate
results of the second analysis against the QC acceptance criteria
only if an analyte fails the first test.

    8.4.4 Repeat the test only for those analytes that failed to
meet the acceptance criteria (P). If these analytes now pass, system
performance is acceptable and analysis of blanks and samples may
proceed. Repeated failure, however, will confirm a general problem
with the measurement system. If this occurs, repeat the test using a
fresh LCS (section 8.2.1) or an LCS prepared with a fresh QC check
sample concentrate (section 8.2.1), or perform and document system
repair. Subsequent to analysis of the LCS prepared with a fresh
sample concentrate, or to system repair, repeat the LCS test
(Section 8.4). If failure of the LCS indicates a systemic problem
with samples in the batch, re-extract and re-analyze the samples in
the batch. See Section 8.1.7 for disposition of repeated failures.
    8.4.5 After analysis of 20 LCS samples, and if the laboratory
chooses to develop and apply optional in-house QC limits, the
laboratory should calculate and apply the optional in-house QC
limits for recovery of future LCS samples (section 8.4). Limits for
recovery in the LCS should be calculated as the mean recovery 3 standard deviations. A minimum of 80% of the analytes tested
for in the LCS must have QC acceptance criteria tighter than those
in Table 4, and the remaining analytes (those not included in the
80%) must meet the acceptance criteria in Table 4. If an in-house
lower limit for recovery is lower than the lower limit in Table 4,
the lower limit in Table 4 must be used, and if an in-house upper
limit for recovery is higher than the upper limit in Table 4, the
upper limit in Table 4 must be used. Many of the analytes and
surrogates do not contain acceptance criteria. The laboratory should
use 60-140% as interim acceptance criteria for recoveries of spiked
analytes and surrogates that do not have recovery limits specified
in Table 4, and at least 80% of the surrogates must meet the 60-140%
interim criteria until in-house LCS and surrogate limits are
developed. Alternatively, acceptance criteria for analytes that do
not have recovery limits in Table 4 may be based on laboratory
control charts. In-house QC acceptance criteria must be updated at
least every two years.
    8.5 Blank--Extract and analyze a blank with each extraction
batch (section 3.1) to demonstrate that the reagents and equipment
used for preparation and analysis are free from contamination.
    8.5.1 Prepare the blank from reagent water and spike it with the
surrogates. The volume of reagent water must be the same as the
volume used for samples, the DOC (section 8.2), the LCS (section
8.4), and the MS/MSD (section 8.3). Extract, concentrate, and
analyze the blank using the same procedures and reagents used for
the samples, LCS, and MS/MSD in the batch. Analyze the blank
immediately after analysis of the LCS (section 8.4) and prior to
analysis of the MS/MSD and samples to demonstrate freedom from
contamination.
    8.5.2 If any analyte of interest is found in the blank at a
concentration greater than the MDL for the analyte, at a
concentration greater than one-third the regulatory compliance
limit, or at a concentration greater than one-tenth the
concentration in a sample in the batch (section 3.1), whichever is
greatest, analysis of samples must be halted and samples in the
batch must be re-extracted and the extracts reanalyzed. Samples in a
batch must be associated with an uncontaminated blank before the
results for those samples may be reported or used for permitting or
regulatory compliance purposes. If re-testing of blanks results in
repeated failures, the laboratory should document the failures and
report the problem and failures with the data.
    8.6 Surrogate recovery--The laboratory must spike all samples
with the surrogate standard spiking solution (section 6.8.6) per
section 10.2.2 or 10.4.2, analyze the samples, and calculate the
percent recovery of each surrogate. QC acceptance criteria for
surrogates must be developed by the laboratory (section 8.4). If any
recovery fails its criterion, attempt to find and correct the cause
of the failure, and if sufficient volume is available, re-extract
another aliquot of the affected sample; otherwise, see section 8.1.7
for disposition of repeated failures.
    8.7 As part of the QC program for the laboratory, it is
suggested but not required that method accuracy for wastewater
samples be assessed and records maintained. After analysis of five
or more spiked wastewater samples as in Section 8.3, calculate the
average percent recovery (X) and the standard deviation of the
percent recovery (sp). Express the accuracy assessment as a percent
interval from X-2sp to X+2sp. For example, if X = 90% and sp = 10%,
the accuracy interval is expressed as 70-110%. Update the accuracy
assessment for each analyte on a regular basis to ensure process
control (e.g., after each 5-10 new accuracy measurements). If
desired, statements of accuracy for laboratory performance,
independent of performance on samples, may be developed using LCSs.
    8.8 It is recommended that the laboratory adopt additional
quality assurance practices for use with this method. The specific
practices that are most productive depend

upon the needs of the laboratory and the nature of the samples.
Field duplicates may be analyzed to assess the precision of
environmental measurements. When doubt exists over the
identification of a peak on the chromatogram, confirmatory
techniques such as gas chromatography with another dissimilar
column, specific element detector, or mass spectrometer must be
used. Whenever possible, the laboratory should analyze standard
reference materials and participate in relevant performance
evaluation studies.

9. Sample Collection, Preservation, and Handling

    9.1 Collect samples as grab samples in glass bottles, or in
refrigerated bottles using automatic sampling equipment. Collect 1-L
of ambient waters, effluents, and other aqueous samples. If high
concentrations of the analytes of interest are expected (e.g., for
untreated effluents or in-process waters), collect a smaller volume
(e.g., 250 mL), but not less than 100 mL, in addition to the 1-L
sample. Follow conventional sampling practices, except do not pre-
rinse the bottle with sample before collection. Automatic sampling
equipment must be as free as possible of polyvinyl chloride or other
tubing or other potential sources of contamination. If needed,
collect additional sample(s) for the MS/MSD (section 8.3).
    9.2 Ice or refrigerate the sample at <=6 [deg]C from the time of
collection until extraction, but do not freeze. If aldrin is to be
determined and residual chlorine is present, add 80 mg/L of sodium
thiosulfate but do not add excess. Any method suitable for field use
may be employed to test for residual chlorine (Reference 14). If
sodium thiosulfate interferes in the determination of the analytes,
an alternative preservative (e.g., ascorbic acid or sodium sulfite)
may be used.
    9.3 Extract all samples within seven days of collection and
completely analyze within 40 days of extraction (Reference 1). If
the sample will not be extracted within 72 hours of collection,
adjust the sample pH to a range of 5.0-9.0 with sodium hydroxide
solution or sulfuric acid. Record the volume of acid or base used.

10. Sample Extraction

    10.1 This section contains procedures for separatory funnel
liquid-liquid extraction (SFLLE, section 10.2), continuous liquid-
liquid extraction (CLLE, section 10.4), and disk-based solid-phase
extraction (SPE, section 10.5). SFLLE is faster, but may not be as
effective as CLLE for extracting polar analytes. SFLLE is labor
intensive and may result in formation of emulsions that are
difficult to break. CLLE is less labor intensive, avoids emulsion
formation, but requires more time (18-24 hours), more hood space,
and may require more solvent. SPE can be faster, unless the
particulate load in an aqueous sample is so high that it slows the
filtration process. If an alternative extraction scheme to those
detailed in this method is used, all QC tests must be performed and
all QC acceptance criteria must be met with that extraction scheme
as an integral part of this method.
    10.2 Separatory funnel liquid-liquid extraction (SFLLE).
    10.2.1 The SFLLE procedure below assumes a sample volume of 1 L.
When a different sample volume is extracted, adjust the volume of
methylene chloride accordingly.
    10.2.2 Mark the water meniscus on the side of the sample bottle
for later determination of sample volume. Pour the entire sample
into the separatory funnel. Pipet the surrogate standard spiking
solution (section 6.8.6) into the separatory funnel. If the sample
will be used for the LCS or MS or MSD, pipet the appropriate QC
check sample concentrate (section 8.3 or 8.4) into the separatory
funnel. Mix well. If the sample arrives in a larger sample bottle, 1
L may be measured in a graduated cylinder, then added to the
separatory funnel.

    Note:  Instances in which the sample is collected in an
oversized bottle should be reported by the laboratory to the data
user. Of particular concern is that fact that this practice
precludes rinsing the empty bottle with solvent as described below,
which could leave hydrophobic pesticides on the wall of the bottle,
and underestimate the actual sample concentrations.

    10.2.3 Add 60 mL of methylene chloride to the sample bottle,
seal, and shake for 30 seconds to rinse the inner surface. Transfer
the solvent to the separatory funnel and extract the sample by
shaking the funnel for two minutes with periodic venting to release
excess pressure. Allow the organic layer to separate from the water
phase for a minimum of 10 minutes. If an emulsion forms and the
emulsion interface between the layers is more than one-third the
volume of the solvent layer, employ mechanical techniques to
complete the phase separation. The optimum technique depends upon
the sample, but may include stirring, filtration of the emulsion
through glass wool, use of phase-separation paper, centrifugation,
salting, freezing, or other physical methods. Collect the methylene
chloride extract in a flask. If the emulsion cannot be broken
(recovery of less than 80% of the methylene chloride, corrected for
the water solubility of methylene chloride), transfer the sample,
solvent, and emulsion into the extraction chamber of a continuous
extractor and proceed as described in section 10.4.
    10.2.4 Add a second 60-mL volume of methylene chloride to the
sample bottle and repeat the extraction procedure a second time,
combining the extracts in the flask. Perform a third extraction in
the same manner. Proceed to macro-concentration (section 10.3.1).
    10.2.5 Determine the original sample volume by refilling the
sample bottle to the mark and transferring the liquid to an
appropriately sized graduated cylinder. Record the sample volume to
the nearest 5 mL. Sample volumes may also be determined by weighing
the container before and after extraction or filling to the mark
with water.
    10.3 Concentration.
    10.3.1 Macro concentration.
    <IP_ADDRESS> Assemble a Kuderna-Danish (K-D) concentrator by
attaching a 10-mL concentrator tube to a 500-mL evaporative flask.
Other concentration devices or techniques may be used in place of
the K-D concentrator so long as the requirements of section 8.2 are
met.
    <IP_ADDRESS> Pour the extract through a solvent-rinsed drying column
containing about 10 cm of anhydrous sodium sulfate, and collect the
extract in the K-D concentrator. Rinse the flask and column with 20-
30 mL of methylene chloride to complete the quantitative transfer.
    <IP_ADDRESS> If no cleanup is to be performed on the sample, add 500
[mu]L (0.5 mL) of isooctane to the extract to act as a keeper during
concentration.
    <IP_ADDRESS> Add one or two clean boiling chips and attach a three-
ball Snyder column to the K-D evaporative flask. Pre-wet the Snyder
column by adding about 1 mL of methylene chloride to the top. Place
the K-D apparatus on a hot water bath (60-65 [deg]C) so that the
concentrator tube is partially immersed in the hot water, and the
entire lower rounded surface of the flask is bathed with hot vapor.
Adjust the vertical position of the apparatus and the water
temperature as required to complete the concentration in 15-20
minutes. At the proper rate of evaporation the balls of the column
will actively chatter but the chambers will not flood with condensed
solvent. When the apparent volume of liquid reaches 1 mL or other
determined amount, remove the K-D apparatus from the water bath and
allow it to drain and cool for at least 10 minutes.
    <IP_ADDRESS> If the extract is to be cleaned up by sulfur removal or
acid back extraction, remove the Snyder column and rinse the flask
and its lower joint into the concentrator tube with 1 to 2 mL of
methylene chloride. A 5-mL syringe is recommended for this
operation. Adjust the final volume to 10 mL in methylene chloride
and proceed to sulfur removal (section 11.5) or acid back extraction
(section 11.6). If the extract is to cleaned up using one of the
other cleanup procedures or is to be injected into the GC, proceed
to Kuderna-Danish micro-concentration (section 10.3.2) or nitrogen
evaporation and solvent exchange (section 10.3.3).
    10.3.2 Kuderna-Danish micro concentration--Add another one or
two clean boiling chips to the concentrator tube and attach a two-
ball micro-Snyder column. Pre-wet the Snyder column by adding about
0.5 mL of methylene chloride to the top. Place the K-D apparatus on
a hot water bath (60-65 [deg]C) so that the concentrator tube is
partially immersed in hot water. Adjust the vertical position of the
apparatus and the water temperature as required to complete the
concentration in 5-10 minutes. At the proper rate of distillation
the balls of the column will actively chatter but the chambers will
not flood with condensed solvent. When the apparent volume of liquid
reaches approximately 1 mL or other required amount, remove the K-D
apparatus from the water bath and allow it to drain and cool for at
least 10 minutes. Remove the Snyder column and rinse the flask and
its lower joint into the concentrator tube with approximately 0.2 mL
of methylene chloride, and proceed to section 10.3.3 for nitrogen
evaporation and solvent exchange.
    10.3.3 Nitrogen evaporation and solvent exchange--Extracts to be
subjected to solid-phase cleanup (SPE) are exchanged into 1.0 mL of
the SPE elution solvent (section <IP_ADDRESS>). Extracts to be subjected
to Florisil[supreg]

or alumina cleanups are exchanged into hexane. Extracts that have
been cleaned up and are ready for analysis are exchanged into
isooctane or hexane, to match the solvent used for the calibration
standards.
    <IP_ADDRESS> Transfer the vial containing the sample extract to the
nitrogen evaporation (blowdown) device (section <IP_ADDRESS>). Lower the
vial into a 50-55 [deg]C water bath and begin concentrating. During
the solvent evaporation process, do not allow the extract to become
dry. Adjust the flow of nitrogen so that the surface of the solvent
is just visibly disturbed. A large vortex in the solvent may cause
analyte loss.
    <IP_ADDRESS> Solvent exchange.
    <IP_ADDRESS>.1 When the volume of the liquid is approximately 500
[mu]L, add 2 to 3 mL of the desired solvent (SPE elution solvent for
SPE cleanup, hexane for Florisil or alumina, or isooctane for final
injection into the GC) and continue concentrating to approximately
500 [mu]L. Repeat the addition of solvent and concentrate once more.
    <IP_ADDRESS>.2 Adjust the volume of an extract to be cleaned up by
SPE, Florisil[supreg], or alumina to 1.0 mL. Proceed to extract
cleanup (section 11).
    <IP_ADDRESS> Extracts that have been cleaned up and are ready for
analysis--Adjust the final extract volume to be consistent with the
volume extracted and the sensitivity desired. The goal is for a
full-volume sample (e.g., 1-L) to have a final extract volume of 10
mL, but other volumes may be used.
    10.3.4 Transfer the concentrated extract to a vial with
fluoropolymer-lined cap. Seal the vial and label with the sample
number. Store in the dark at room temperature until ready for GC
analysis. If GC analysis will not be performed on the same day,
store the vial in the dark at <=6 [deg]C. Analyze the extract by GC
per the procedure in section 12.
    10.4 Continuous liquid/liquid extraction (CLLE).
    10.4.1 Use CLLE when experience with a sample from a given
source indicates an emulsion problem, or when an emulsion is
encountered using SFLLE. CLLE may be used for all samples, if
desired.
    10.4.2 Mark the water meniscus on the side of the sample bottle
for later determination of sample volume. Transfer the sample to the
continuous extractor and, using a pipet, add surrogate standard
spiking solution. If the sample will be used for the LCS, MS, or
MSD, pipet the appropriate check sample concentrate (section 8.2.1
or 8.3.2) into the separatory funnel. Mix well. Add 60 mL of
methylene chloride to the sample bottle, seal, and shake for 30
seconds to rinse the inner surface. Transfer the solvent to the
extractor.
    10.4.3 Repeat the sample bottle rinse with two additional 50-100
mL portions of methylene chloride and add the rinses to the
extractor.
    10.4.4 Add a suitable volume of methylene chloride to the
distilling flask (generally 200-500 mL) and sufficient reagent water
to ensure proper operation of the extractor, and extract the sample
for 18-24 hours. A shorter or longer extraction time may be used if
all QC acceptance criteria are met. Test and, if necessary, adjust
the pH of the water to a range of 5.0-9.0 during the second or third
hour of the extraction. After extraction, allow the apparatus to
cool, then detach the distilling flask. Dry, concentrate, solvent
exchange, and transfer the extract to a vial with fluoropolymer-
lined cap, per Section 10.3.
    10.4.5 Determine the original sample volume by refilling the
sample bottle to the mark and transferring the liquid to an
appropriately sized graduated cylinder. Record the sample volume to
the nearest 5 mL. Sample volumes may also be determined by weighing
the container before and after extraction or filling to the mark
with water.
    10.5 Solid-phase extraction of aqueous samples. The steps in
this section address the extraction of aqueous field samples using
disk-based solid-phase extraction (SPE) media, based on an ATP
approved by EPA in 1995 (Reference 20). This application of SPE is
distinct from that used in this method for the cleanup of sample
extracts in section 11.2. Analysts must be careful not to confuse
the equipment, supplies, or the procedural steps from these two
different uses of SPE.

    Note:  Changes to the extraction conditions described below may
be made by the laboratory under the allowance for method flexibility
described in section 8.1, provided that the performance requirements
in section 8.2 are met. However, changes in SPE materials, formats,
and solvents must meet the requirements in section 8.1.2 and its
subsections.

    10.5.1 Mark the water meniscus on the side of the sample bottle
for later determination of sample volume. If the sample contains
particulates, let stand to settle out the particulates before
extraction.
    10.5.2 Extract the sample as follows:
    <IP_ADDRESS> Place a 90-mm standard filter apparatus on a vacuum
filtration flask or manifold and attach to a vacuum source. The
vacuum gauge must read at least 25 in. of mercury when all valves
are closed. Position a 90-mm C18 extraction disk onto the filter
screen. Wet the entire disk with methanol. To aid in filtering
samples with particulates, a 1-[mu]m glass fiber filter or
Empore[supreg] Filter Aid 400 can be placed on the top of the disk
and wetted with methanol. Install the reservoir and clamp. Resume
vacuum to dry the disk. Interrupt the vacuum. Wash the disk and
reservoir with 20 mL of methylene chloride. Resume the vacuum
briefly to pull methylene chloride through the disk. Interrupt the
vacuum and allow the disk to soak for about a minute. Resume vacuum
and completely dry the disk.
    <IP_ADDRESS> Condition the disk with 20 mL of methanol. Apply vacuum
until nearly all the solvent has passed through the disk,
interrupting it while solvent remains on the disk. Allow the disk to
soak for about a minute. Resume vacuum to pull most of the methanol
through, but interrupting it to leave a layer of methanol on the
surface of the disk. Do not allow disk to dry. For uniform flow and
good recovery, it is critical the disk not be allowed to dry from
now until the end of the extraction. Discard waste solvent. Rinse
the disk with 20 mL of deionized water. Resume vacuum to pull most
of the water through, but interrupt it to leave a layer of water on
the surface of the disk. Do not allow the disk to dry. If disk does
dry, recondition with methanol as above.
    <IP_ADDRESS> Add the water sample to the reservoir and immediately
apply the vacuum. If particulates have settled in the sample, gently
decant the clear layer into the apparatus until most of the sample
has been processed. Then pour the remainder including the
particulates into the reservoir. Empty the sample bottle completely.
When the filtration is complete, dry the disk for three minutes.
Turn off the vacuum.
    10.5.3 Discard sample filtrate. Insert tube to collect the
eluant. The tube should fit around the drip tip of the base.
Reassemble the apparatus. Add 5.0 mL of acetone to the center of the
disk, allowing it to spread evenly over the disk. Turn the vacuum on
and quickly off when the filter surface nears dryness but still
remains wet. Allow to soak for 15 seconds. Add 20 mL of methylene
chloride to the sample bottle, seal and shake to rinse the inside of
the bottle. Transfer the methylene chloride from the bottle to the
filter. Resume the vacuum slowly so as to avoid splashing.
    Interrupt the vacuum when the filter surface nears dryness but
still remains wet. Allow disk to soak in solvent for 20 seconds.
Rinse the reservoir glass and disk with 10 mL of methylene chloride.
Resume vacuum slowly. Interrupt vacuum when disk is covered with
solvent. Allow to soak for 20 seconds. Resume vacuum to dry the
disk. Remove the sample tube.
    10.5.4 Dry, concentrate, solvent exchange, and transfer the
extract to a vial with fluoropolymer-lined cap, per section 10.3.
    10.5.5 Determine the original sample volume by refilling the
sample bottle to the mark and transferring the liquid to an
appropriately sized graduated cylinder. Record the sample volume to
the nearest 5 mL. Sample volumes may also be determined by weighing
the container before and after extraction or filling to the mark
with water.

11. Extract Cleanup

    11.1 Cleanup may not be necessary for relatively clean samples
(e.g., treated effluents, groundwater, drinking water). If
particular circumstances require the use of a cleanup procedure, the
laboratory may use any or all of the procedures below or any other
appropriate procedure (e.g., gel permeation chromatography).
However, the laboratory must first repeat the tests in sections 8.2,
8.3, and 8.4 to demonstrate that the requirements of those sections
can be met using the cleanup procedure(s) as an integral part of
this method. This is particularly important when the target analytes
for the analysis include any of the single component pesticides in
Table 2, because some cleanups have not been optimized for all of
those analytes.
    11.1.1 The solid-phase cartridge (section 11.2) removes polar
organic compounds such as phenols.
    11.1.2 The Florisil[supreg] column (section 11.3) allows for
selected fractionation of the organochlorine analytes and will also
eliminate polar interferences.
    11.1.3 Alumina column cleanup (section 11.4) also removes polar
materials.
    11.1.4 Elemental sulfur, which interferes with the electron
capture gas chromatography of some of the pesticides,

may be removed using activated copper, or TBA sulfite. Sulfur
removal (section 11.5) is required when sulfur is known or suspected
to be present. Some chlorinated pesticides which also contain sulfur
may be removed by this cleanup.
    11.1.5 Acid back extraction (section 11.6) may be useful for
cleanup of PCBs and other compounds not adversely affected by
sulfuric acid.
    11.2 Solid-phase extraction (SPE) as a cleanup. In order to use
the C18 SPE cartridge in section <IP_ADDRESS> as a cleanup procedure, the
sample extract must be exchanged from methylene chloride to
methylene chloride:acetonitrile:hexane (50:3:47). Follow the solvent
exchange steps in section <IP_ADDRESS> prior to attempting solid-phase
cleanup.

    Note: This application of SPE is distinct from that used in this
method for the extraction of aqueous samples in section 10.5.
Analysts must be careful not to confuse the equipment, supplies, or
procedural steps from these two different uses of SPE.

    11.2.1 Setup.
    <IP_ADDRESS> Attach the VacElute Manifold (section <IP_ADDRESS>) to a
water aspirator or vacuum pump with the trap and gauge installed
between the manifold and vacuum source.
    <IP_ADDRESS> Place the SPE cartridges in the manifold, turn on the
vacuum source, and adjust the vacuum to 5 to 10 psi.
    11.2.2 Cartridge washing--Pre-elute each cartridge prior to use
sequentially with 10-mL portions each of hexane, methanol, and water
using vacuum for 30 seconds after each eluting solvent. Follow this
pre-elution with 1 mL methylene chloride and three 10-mL portions of
the elution solvent (section <IP_ADDRESS>) using vacuum for 5 minutes
after each eluting solvent. Tap the cartridge lightly while under
vacuum to dry between solvent rinses. The three portions of elution
solvent may be collected and used as a cartridge blank, if desired.
Finally, elute the cartridge with 10 mL each of methanol and water,
using the vacuum for 30 seconds after each eluant.
    11.2.3 Extract cleanup.
    <IP_ADDRESS> After cartridge washing (section 11.2.2), release the
vacuum and place the rack containing the 50-mL volumetric flasks
(section <IP_ADDRESS>) in the vacuum manifold. Re-establish the vacuum at
5 to 10 psi.
    <IP_ADDRESS> Using a pipette or a 1-mL syringe, transfer 1.0 mL of
extract to the SPE cartridge. Apply vacuum for five minutes to dry
the cartridge. Tap gently to aid in drying.
    <IP_ADDRESS> Elute each cartridge into its volumetric flask
sequentially with three 10-mL portions of the methylene
chloride:acetonitrile:hexane (50:3:47) elution solvent (section
<IP_ADDRESS>), using vacuum for five minutes after each portion. Collect
the eluants in the 50-mL volumetric flasks.
    <IP_ADDRESS> Release the vacuum and remove the 50-mL volumetric
flasks.
    <IP_ADDRESS> Concentrate the eluted extracts per Section 10.3.
    11.3 Florisil[supreg]. In order to use Florisil cleanup, the
sample extract must be exchanged from methylene chloride to hexane.
Follow the solvent exchange steps in section <IP_ADDRESS> prior to
attempting Florisil[supreg] cleanup.

    Note: Alternative formats for this cleanup may be used by the
laboratory, including cartridges containing Florisil[supreg]. If an
alternative format is used, consult the manufacturer's instructions
and develop a formal documented procedure to replace the steps in
section 11.3 of this method and demonstrate that the alternative
meets the relevant quality control requirements of this method.

    11.3.1 If the chromatographic column does not contain a frit at
the bottom, place a small plug of pre-cleaned glass wool in the
column (section 5.2.4) to retain the Florisil[supreg]. Place the
mass of Florisil[supreg] (nominally 20 g) predetermined by
calibration (section 7.8 and Table 6) in a chromatographic column.
Tap the column to settle the Florisil[supreg] and add 1 to 2 cm of
granular anhydrous sodium sulfate to the top.
    11.3.2 Add 60 mL of hexane to wet and rinse the sodium sulfate
and Florisil[supreg]. Just prior to exposure of the sodium sulfate
layer to the air, stop the elution of the hexane by closing the
stopcock on the chromatographic column. Discard the eluant.
    11.3.3 Transfer the concentrated extract (section 10.3.3) onto
the column. Complete the transfer with two 1-mL hexane rinses,
drawing the extract and rinses down to the level of the sodium
sulfate.
    11.3.4 Place a clean 500-mL K-D flask and concentrator tube
under the column. Elute Fraction 1 with 200 mL of 6% (v/v) ethyl
ether in hexane at a rate of approximately 5 mL/min. Remove the K-D
flask and set it aside for later concentration. Elute Fraction 2
with 200 mL of 15% (v/v) ethyl ether in hexane into a second K-D
flask. Elute Fraction 3 with 200 mL of 50% (v/v) ethyl ether in
hexane into a third K-D flask. The elution patterns for the
pesticides and PCBs are shown in Table 6.
    11.3.5 Concentrate the fractions as in Section 10.3, except use
hexane to prewet the column and set the water bath at about 85
[deg]C. When the apparatus is cool, remove the Snyder column and
rinse the flask and its lower joint into the concentrator tube with
hexane. Adjust the volume of Fraction 1 to approximately 10 mL for
sulfur removal (Section 11.5), if required; otherwise, adjust the
volume of the fractions to 10 mL, 1.0 mL, or other volume needed for
the sensitivity desired. Analyze the concentrated extract by gas
chromatography (Section 12).
    11.4 Alumina. The sample extract must be exchanged from
methylene chloride to hexane. Follow the solvent exchange steps in
section <IP_ADDRESS> prior to attempting alumina cleanup.
    11.4.1 If the chromatographic column does not contain a frit at
the bottom, place a small plug of pre-cleaned glass wool in the
chromatographic column (section 5.2.4) to retain the alumina. Add 10
g of alumina (section 6.7.3) on top of the plug. Tap the column to
settle the alumina. Place 1-2 g of anhydrous sodium sulfate on top
of the alumina.
    11.4.2 Close the stopcock and fill the column to just above the
sodium sulfate with hexane. Add 25 mL of hexane. Open the stopcock
and adjust the flow rate of hexane to approximately 2 mL/min. Do not
allow the column to go dry throughout the elutions.
    11.4.3 When the level of the hexane is at the top of the column,
quantitatively transfer the extract to the column. When the level of
the extract is at the top of the column, slowly add 25 mL of hexane
and elute the column to the level of the sodium sulfate. Discard the
hexane.
    11.4.4 Place a K-D flask (section <IP_ADDRESS>.2) under the column
and elute the pesticides with approximately 150 mL of hexane:ethyl
ether (80:20 v/v). It may be necessary to adjust the volume of
elution solvent for slightly different alumina activities.
    11.4.5 Concentrate the extract per section 10.3.
    11.5 Sulfur removal--Elemental sulfur will usually elute in
Fraction 1 of the Florisil[supreg] column cleanup. If
Florisil[supreg] cleanup is not used, or to remove sulfur from any
of the Florisil[supreg] fractions, use one of the sulfur removal
procedures below. These procedures may be applied to extracts in
hexane, ethyl ether, or methylene chloride.

    Note: Separate procedures using copper or TBA sulfite are
provided in this section for sulfur removal. They may be used
separately or in combination, if desired.

    11.5.1 Removal with copper (Reference 15).

    Note: Some of the analytes in Table 2 are not amenable to sulfur
removal with copper (e.g., atrazine and diazinon). Therefore, before
using copper to remove sulfur from an extract that will be analyzed
for any of the non-PCB analytes in Table 2, the laboratory must
demonstrate that the analytes can be extracted from an aqueous
sample matrix that contains sulfur and recovered from an extract
treated with copper. Acceptable performance can be demonstrated
through the preparation and analysis of a matrix spike sample that
meets the QC requirements for recovery.

    <IP_ADDRESS> Quantitatively transfer the extract to a 40- to 50-mL
flask or bottle. If there is evidence of water in the K-D or round-
bottom flask after the transfer, rinse the flask with small portions
of hexane:acetone (40:60) and add to the flask or bottle. Mark and
set aside the concentration flask for future use.
    <IP_ADDRESS> Add 10-20 g of granular anhydrous sodium sulfate to the
flask. Swirl to dry the extract.
    <IP_ADDRESS> Add activated copper (section <IP_ADDRESS>.4) and allow to
stand for 30-60 minutes, swirling occasionally. If the copper does
not remain bright, add more and swirl occasionally for another 30-60
minutes.
    <IP_ADDRESS> After drying and sulfur removal, quantitatively
transfer the extract to a nitrogen-evaporation vial or tube and
proceed to section 10.3.3 for nitrogen evaporation and solvent
exchange, taking care to leave the sodium sulfate and copper foil in
the flask.
    11.5.2 Removal with TBA sulfite.
    <IP_ADDRESS> Using small volumes of hexane, quantitatively transfer
the extract to a 40- to 50-mL centrifuge tube with fluoropolymer-
lined screw cap.
    <IP_ADDRESS> Add 1-2 mL of TBA sulfite reagent (section <IP_ADDRESS>.4),
2-3 mL of 2-propanol, and approximately 0.7 g of sodium sulfite
(section <IP_ADDRESS>.2) crystals to

the tube. Cap and shake for 1-2 minutes. If the sample is colorless
or if the initial color is unchanged, and if clear crystals
(precipitated sodium sulfite) are observed, sufficient sodium
sulfite is present. If the precipitated sodium sulfite disappears,
add more crystalline sodium sulfite in approximately 0.5-g portions
until a solid residue remains after repeated shaking.
    <IP_ADDRESS> Add 5-10 mL of reagent water and shake for 1-2 minutes.
Centrifuge to settle the solids.
    <IP_ADDRESS> Quantitatively transfer the hexane (top) layer through
a small funnel containing a few grams of granular anhydrous sodium
sulfate to a nitrogen-evaporation vial or tube and proceed to
section 10.3.3 for micro-concentration and solvent exchange.
    11.6 Acid back extraction (section 6.1.2).
    11.6.1 Quantitatively transfer the extract (section <IP_ADDRESS>) to
a 250-mL separatory funnel.
    11.6.2 Partition the extract against 50 mL of sulfuric acid
solution (section 6.1.2). Discard the aqueous layer. Repeat the acid
washing until no color is visible in the aqueous layer, to a maximum
of four washings.
    11.6.3 Partition the extract against 50 mL of sodium chloride
solution (section 6.7.5). Discard the aqueous layer.
    11.6.4 Proceed to section 10.3.3 for micro-concentration and
solvent exchange.

12. Gas Chromatography

    12.1 Establish the same operating conditions used in section 7.1
for instrument calibration.
    12.2 If the internal standard calibration procedure is used, add
the internal standard solution (section 6.9.3) to the extract as
close as possible to the time of injection to minimize the
possibility of loss by evaporation, adsorption, or reaction. For
example, add 1 [mu]L of 10 [mu]g/mL internal standard solution into
the extract, assuming no dilutions. Mix thoroughly.
    12.3 Simultaneously inject an appropriate volume of the sample
extract or standard solution onto both columns, using split,
splitless, solvent purge, large-volume, or on-column injection.
Alternatively, if using a single-column GC configuration, inject an
appropriate volume of the sample extract or standard solution onto
each GC column independently. If the sample is injected manually,
the solvent-flush technique should be used. The injection volume
depends upon the technique used and the sensitivity needed to meet
MDLs or reporting limits for regulatory compliance. Injection
volumes must be the same for all extracts. Record the volume
injected to the nearest 0.05 [mu]L.
    12.4 Set the data system or GC control to start the temperature
program upon sample injection, and begin data collection after the
solvent peak elutes. Set the data system to stop data collection
after the last analyte is expected to elute and to return the column
to the initial temperature.
    12.5 Perform all qualitative and quantitative measurements as
described in Sections 14 and 15. When standards and extracts are not
being used for analyses, store them refrigerated at <6 [deg]C,
protected from light, in screw-cap vials equipped with un-pierced
fluoropolymer-lined septa.

13. System and Laboratory Performance

    13.1 At the beginning of each shift during which standards or
extracts are analyzed, GC system performance and calibration must be
verified for all analytes and surrogates on both column/detector
systems. Adjustment and/or recalibration (per section 7) are
performed until all performance criteria are met. Only after all
performance criteria are met may samples, blanks and other QC
samples, and standards be analyzed.
    13.2 Inject an aliquot of the calibration verification standard
(section 6.8.4) on both columns. Inject an aliquot of each of the
multi-component standards.
    13.3 Retention times--The absolute retention times of the peak
maxima shall be within 2 seconds of the retention times
in the calibration verification (section 7.8).
    13.4 GC resolution--Resolution is acceptable if the valley
height between two peaks (as measured from the baseline) is less
than 40% of the shorter of the two peaks.
    13.4.1 DB-608 column--DDT and endrin aldehyde
    13.4.2 DB-1701 column--alpha and gamma chlordane

    Note: If using other GC columns or stationary phases, these
resolution criteria apply to these four target analytes and any
other closely eluting analytes on those other GC columns.

    13.5 Decomposition of DDT and endrin--If DDT, endrin, or their
breakdown products are to be determined, this test must be performed
prior to calibration verification (section 13.6). DDT decomposes to
DDE and DDD. Endrin decomposes to endrin aldehyde and endrin ketone.
    13.5.1 Inject 1 [mu]L of the DDT and endrin decomposition
solution (section 6.8.7). As noted in section 6.8.7, other injection
volumes may be used as long as the concentrations of DDT and endrin
in the solution are adjusted to introduce the masses of the two
analytes into the instrument that are listed in section 6.8.7.
    13.5.2 Measure the areas of the peaks for DDT, DDE, DDD, endrin,
endrin aldehyde, and endrin ketone in the chromatogram and calculate
the percent breakdown as shown in the equations below:
[GRAPHIC] [TIFF OMITTED] TR28AU17.005

    13.5.3 Both the % breakdown of DDT and of endrin must be less
than 20%, otherwise the system is not performing acceptably for DDT
and endrin. In this case, repair the GC column system that failed
and repeat the performance tests (sections 13.2 to 13.6) until the
specification is met.

    Note: DDT and endrin decomposition are usually caused by
accumulations of particulates in the injector and in the front end
of the column. Cleaning and silanizing the injection port liner, and
breaking off a short section of the front end of the column will
usually eliminate the decomposition problem. Either of these
corrective actions may affect retention times, GC resolution, and
calibration linearity.

    13.6 Calibration verification.
    13.6.1 Compute the percent recovery of each analyte and of the
coeluting analytes, based on the initial calibration data (section
7.5 or 7.6).
    13.6.2 For each analyte or for coeluting analytes, compare the
concentration with the limits for calibration verification in Table
4. For coeluting analytes, use the coeluting analyte with the least
restrictive specification (the widest range). For analytes in Table
2 not listed in Table 4, QC acceptance criteria must be developed by
the laboratory. EPA has provided guidance for development of QC
acceptance criteria (References 13 and 14). If the recoveries for
all analytes meet the acceptance criteria, system performance is
acceptable and analysis of blanks and samples may continue. If,
however, any recovery falls outside the calibration verification
range, system performance is unacceptable for that analyte. If this
occurs, repair the system and repeat the test (section 13.6), or
prepare a fresh calibration standard and repeat the test, or
recalibrate (section 7). See Section 8.1.7 for information on
repeated test failures.
    13.7 Laboratory control sample.
    13.7.1 Analyze the extract of the LCS (section 6.8.3) extracted
with each sample batch (Section 8.4). See Section 8.4 for criteria
acceptance of the LCS.
    13.7.2 It is suggested, but not required, that the laboratory
update statements of data

quality. Add results that pass the specifications in section 13.7.3
to initial (section 8.7) and previous ongoing data. Update QC charts
to form a graphic representation of continued laboratory
performance. Develop a statement of laboratory data quality for each
analyte by calculating the average percent recovery (R) and the
standard deviation of percent recovery, sr. Express the accuracy as
a recovery interval from R - 2sr to R + 2sr. For example, if R = 95%
and sr = 5%, the accuracy is 85 to 105%.
    13.8 Internal standard response--If internal standard
calibration is used, verify that detector sensitivity has not
changed by comparing the response (area or height) of each internal
standard in the sample, blank, LCS, MS, and MSD to the response in
calibration verification (section 6.8.3). The peak area or height of
the internal standard should be within 50% to 200% (\1/2\ to 2x) of
its respective peak area or height in the verification standard. If
the area or height is not within this range, compute the
concentration of the analytes using the external standard method
(section 7.5). If the analytes are affected, re-prepare and
reanalyze the sample, blank, LCS, MS, or MSD, and repeat the
pertinent test.

14. Qualitative Identification

    14.1 Identification is accomplished by comparison of data from
analysis of a sample, blank, or other QC sample with data from
calibration verification (section 7.7.1 or 13.5), and with data
stored in the retention-time and calibration libraries (section
7.7). The retention time window is determined as described in
section 14.2. Identification is confirmed when retention time agrees
on both GC columns, as described below. Alternatively, GC/MS
identification may be used to provide another means of
identification.
    14.2 Establishing retention time windows.
    14.2.1 Using the data from the multi-point initial calibration
(section 7.4), determine the retention time in decimal minutes (not
minutes:seconds) of each peak representing a single-component target
analyte on each column/detector system. For the multi-component
analytes, use the retention times of the five largest peaks in the
chromatograms on each column/detector system.
    14.2.2 Calculate the standard deviation of the retention times
for each single-component analyte on each column/detector system and
for the three to five exclusive (unique large) peaks for each multi-
component analyte.
    14.2.3 Define the width of the retention time window as three
times that standard deviation. Establish the center of the retention
time window for each analyte by using the absolute retention time
for each analyte from the calibration verification standard at the
beginning of the analytical shift. For samples run during the same
shift as an initial calibration, use the retention time of the mid-
point standard of the initial calibration. If the calculated RT
window is less than 0.02 minutes, then use 0.02 minutes as the
window.

    Note: Procedures for establishing retention time windows from
other sources may be employed provided that they are clearly
documented and provide acceptable performance. Such performance may
be evaluated using the results for the spiked QC samples described
in this method, such as laboratory control samples and matrix spike
samples.

    14.2.4 The retention time windows must be recentered when a new
GC column is installed or if a GC column has been shortened during
maintenance to a degree that the retention times of analytes in the
calibration verification standard have shifted close to the lower
limits of the established retention time windows.
    14.2.5 RT windows should be checked periodically by examining
the peaks in spiked samples such as the LCS or MS/MSD to confirm
that peaks for known analytes are properly identified.
    14.2.6 If the retention time of an analyte in the calibration
(Section 7.4) varies by more than 5 seconds across the calibration
range as a function of the concentration of the standard, using the
standard deviation of the retention times (section 14.2.3) to set
the width of the retention time window may not adequately serve to
identify the analyte in question under routine conditions. In such
cases, data from additional analyses of standards may be required to
adequately model the chromatographic behavior of the analyte.
    14.3 Identifying the analyte in a sample.
    14.3.1 In order to identify a single-component analyte from
analysis of a sample, blank, or other QC sample, the peak
representing the analyte must fall within its respective retention
time windows on both column/detector systems (as defined in section
14.2). That identification is further supported by the comparison of
the numerical results on both columns, as described in section 15.7.
    14.3.2 In order to identify a multi-component analyte, pattern
matching (fingerprinting) may be used, or the three to five
exclusive (unique and largest) peaks for that analyte must fall
within their respective retention time windows on both column/
detector systems (as defined in section 14.2). That identification
is further supported by the comparison of the numerical results on
both columns, as described in section 15.7. Alternatively, GC/MS
identification may be used. Differentiation among some of the
Aroclors may require evaluation of more than five peaks to ensure
correct identification.
    14.4 GC/MS confirmation. When the concentration of an analyte is
sufficient and the presence or identity is suspect, its presence
should be confirmed by GC/MS. In order to match the sensitivity of
the GC/ECD, confirmation would need to be by GC/MS-SIM, or the
estimated concentration would need to be 100 times higher than the
GC/ECD calibration range. The extract may be concentrated by an
additional amount to allow a further attempt at GC/MS confirmation.
    14.5 Additional information that may aid the laboratory in the
identification of an analyte. The occurrence of peaks eluting near
the retention time of an analyte of interest increases the
probability of a false positive for the analyte. If the
concentration is insufficient for confirmation by GC/MS, the
laboratory may use the cleanup procedures in this method (section
11) on a new sample aliquot to attempt to remove the interferent.
After attempts at cleanup are exhausted, the following steps may be
helpful to assure that the substance that appears in the RT windows
on both columns is the analyte of interest.
    14.5.1 Determine the consistency of the RT data for the analyte
on each column. For example, if the RT is very stable (i.e., varies
by no more than a few seconds) for the calibration, calibration
verification, blank, LCS, and MS/MSD, the RT for the analyte of
interest in the sample should be within this variation regardless of
the window established in Section 14.2. If the analyte is not within
this variation on both columns, it is likely not present.
    14.5.2 The possibility exists that the RT for the analyte in a
sample could shift if extraneous materials are present. This
possibility may be able to be confirmed or refuted by the behavior
of the surrogates in the sample. If multiple surrogates are used
that span the length of the chromatographic run, the RTs for the
surrogates on both columns are consistent with their RTs in
calibration, calibration verification, blank, LCS, and MS/MSD, it is
unlikely that the RT for the analyte of interest has shifted.
    14.5.3 If the RT for the analyte is shifted slightly later on
one column and earlier on the other, and the surrogates have not
shifted, it is highly unlikely that the analyte is present, because
shifts nearly always occur in the same direction on both columns.

15. Quantitative Determination

    15.1 External standard quantitation--Calculate the concentration
of the analyte in the extract using the calibration curve or average
calibration factor determined in calibration (section 7.5.2) and the
following equation:
[GRAPHIC] [TIFF OMITTED] TR28AU17.006

where:

Cex = Concentration of the analyte in the extract (ng/mL)
As = Peak height or area for the analyte in the standard
or sample
CF = Calibration factor, as defined in Section 7.5.1

    15.2 Internal standard quantitation--Calculate the concentration
of the analyte in the extract using the calibration curve or average
response factor determined in calibration (section 7.6.2) and the
following equation:
[GRAPHIC] [TIFF OMITTED] TR28AU17.007

where:

Cex = Concentration of the analyte in the extract (ng/mL)
As = Peak height or area for the analyte in the standard
or sample
Cis = Concentration of the internal standard (ng/mL)

Ais = Area of the internal standard
RF = Response factor, as defined in section 7.6.1

    15.3 Calculate the concentration of the analyte in the sample
using the concentration in the extract, the extract volume, the
sample volume, and the dilution factor, per the following equation:
[GRAPHIC] [TIFF OMITTED] TR28AU17.008

where:

Cs = Concentration of the analyte in the sample
([micro]g/L)
Vex = Final extract volume (mL)
Cex = Concentration in the extract (ng/mL)
Vs = Volume of sample (L)
DF = Dilution factor

and the factor of 1,000 in the denominator converts the final units
from ng/L to [micro]g/L
    15.4 If the concentration of any target analyte exceeds the
calibration range, either extract and analyze a smaller sample
volume, or dilute and analyze the diluted extract.
    15.5 Quantitation of multi-component analytes.
    15.5.1 PCBs as Aroclors. Quantify an Aroclor by comparing the
sample chromatogram to that of the most similar Aroclor standard as
indicated in section 14.3.2. Compare the responses of 3 to 5 major
peaks in the calibration standard for that Aroclor with the peaks
observed in the sample extract. The amount of Aroclor is calculated
using the individual calibration factor for each of the 3 to 5
characteristic peaks chosen in section 7.5.1. Determine the
concentration of each of the characteristic peaks, using the average
calibration factor calculated for that peak in section 7.5.2, and
then those 3 to 5 concentrations are averaged to determine the
concentration of that Aroclor.
    15.5.2 Other multi-component analytes. Quantify any other multi-
component analytes (technical chlordane or toxaphene) using the same
peaks used to develop the average calibration factors in section
7.5.2. Determine the concentration of each of the characteristic
peaks, and then the concentrations represented by those
characteristic peaks are averaged to determine the concentration of
the analyte. Alternatively, for toxaphene, the analyst may determine
the calibration factor in section 7.5.2 by summing the areas of all
of the peaks for the analyte and using the summed of the peak areas
in the sample chromatogram to determine the concentration. However,
the approach used for toxaphene must be the same for the calibration
and the sample analyses.
    15.6 Reporting of results. As noted in section 1.6.1, EPA has
promulgated this method at 40 CFR part 136 for use in wastewater
compliance monitoring under the National Pollutant Discharge
Elimination System (NPDES). The data reporting practices described
here are focused on such monitoring needs and may not be relevant to
other uses of the method.
    15.6.1 Report results for wastewater samples in [micro]g/L
without correction for recovery. (Other units may be used if
required by in a permit.) Report all QC data with the sample
results.
    15.6.2 Reporting level. Unless specified otherwise by a
regulatory authority or in a discharge permit, results for analytes
that meet the identification criteria are reported down to the
concentration of the ML established by the laboratory through
calibration of the instrument (see section 7.5 or 7.6 and the
glossary for the derivation of the ML). EPA considers the terms
``reporting limit,'' ``quantitation limit,'' and ``minimum level''
to be synonymous.
    <IP_ADDRESS> Report the lower result from the two columns (see
section 15.7 below) for each analyte in each sample or QC standard
at or above the ML to 3 significant figures. Report a result for
each analyte in each sample or QC standard below the ML as ``12, are hazardous and must be
handled and disposed of as hazardous waste, or neutralized and
disposed of in accordance with all federal, state, and local
regulations. It is the laboratory's responsibility to comply with
all federal, state, and local regulations governing waste
management, particularly the hazardous waste identification rules
and land disposal restrictions. The laboratory using this method has
the responsibility to protect the air, water, and land by minimizing
and controlling all releases from fume hoods and bench operations.
Compliance is also required with any sewage discharge permits and
regulations. For further information on waste management, see ``The
Waste Management Manual for Laboratory Personnel,'' also available
from the American Chemical Society at the address in section 18.3.
    19.3 Many analytes in this method decompose above 500 [deg]C.
Low-level waste such as absorbent paper, tissues, animal remains,
and plastic gloves may be burned in an appropriate incinerator.
Gross quantities of neat or highly concentrated solutions of toxic
or hazardous chemicals should be packaged securely and disposed of
through commercial or governmental channels that are capable of
handling toxic wastes.
    19.4 For further information on waste management, consult The
Waste Management Manual for Laboratory Personnel and Less is Better-
Laboratory Chemical Management for Waste Reduction, available from
the American Chemical Society's Department of Government Relations
and Science Policy, 1155 16th Street NW., Washington, DC 20036, 202-
872-4477.

20. References

1. ``Determination of Pesticides and PCBs in Industrial and
Municipal Wastewaters,'' EPA 600/4-82-023, National Technical
Information Service, PB82-214222, Springfield, Virginia 22161, April
1982.
2. ``EPA Method Study 18 Method 608-Organochlorine Pesticides and
PCBs,'' EPA 600/4-84-061, National Technical Information Service,
PB84-211358, Springfield, Virginia 22161, June 1984.
3. ``Method Detection Limit and Analytical Curve Studies, EPA
Methods 606, 607, and 608,'' Special letter report for EPA Contract
68-03-2606, U.S. Environmental Protection Agency, Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio 45268, June
1980.
4. ASTM Annual Book of Standards, Part 31, D3694-78. ``Standard
Practice for Preparation of Sample Containers and for Preservation
of Organic Constituents,'' American Society for Testing and
Materials, Philadelphia.
5. Giam, C.S., Chan, H.S., and Nef, G.S. ``Sensitive Method for
Determination of Phthalate Ester Plasticizers in Open-Ocean Biota
Samples,'' Analytical Chemistry, 47:2225 (1975).
6. Giam, C.S. and Chan, H.S. ``Control of Blanks in the Analysis of
Phthalates in Air and Ocean Biota Samples,'' U.S. National Bureau of
Standards, Special Publication 442, pp. 701-708, 1976.
7. Solutions to Analytical Chemistry Problems with Clean Water Act
Methods, EPA 821-R-07-002, March 2007.
8. ``Carcinogens-Working With Carcinogens,'' Department of Health,
Education, and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health,
Publication No. 77-206, August 1977.
9. ``Occupational Exposure to Hazardous Chemicals in Laboratories,''
(29 CFR 1910.1450), Occupational Safety and Health Administration,
OSHA.
10. 40 CFR 136.6(b)(4)(j).
11. Mills, P.A. ``Variation of Florisil Activity: Simple Method for
Measuring Absorbent Capacity and Its Use in Standardizing

Florisil Columns,'' Journal of the Association of Official
Analytical Chemists, 51:29, (1968).
12. 40 CFR 136.6(b)(2)(i).
13. Protocol for EPA Approval of New Methods for Organic and
Inorganic Analytes in Wastewater and Drinking Water (EPA-821-B-98-
003) March 1999.
14. Methods 4500 Cl F and 4500 Cl G, Standard Methods for the
Examination of Water and Wastewater, published jointly by the
American Public Health Association, American Water Works
Association, and Water Environment Federation, 1015 Fifteenth St.,
Washington, DC 20005, 20th Edition, 2000.
15. ``Manual of Analytical Methods for the Analysis of Pesticides in
Human and Environmental Samples,'' EPA-600/8-80-038, U.S.
Environmental Protection Agency, Health Effects Research Laboratory,
Research Triangle Park, North Carolina.
16. USEPA, 2000, Method 1656 Organo-Halide Pesticides In Wastewater,
Soil, Sludge, Sediment, and Tissue by GC/HSD, EPA-821-R-00-017,
September 2000.
17. USEPA, 2010, Method 1668C Chlorinated Biphenyl Congeners in
Water, Soil, Sediment, Biosolids, and Tissue by HRGC/HRMS, EPA-820-
R-10-005, April 2010.
18. USEPA, 2007, Method 1699: Pesticides in Water, Soil, Sediment,
Biosolids, and Tissue by HRGC/HRMS, EPA-821-R-08-001, December 2007.
19. ``Less is Better,'' American Chemical Society on-line
publication, http://www.acs.org/content/dam/acsorg/about/governance/committees/chemicalsafety/publications/less-is-better.pdf.
20. EPA Method 608 ATP 3M0222, An alternative test procedure for the
measurement of organochlorine pesticides and polychlorinated
biphenyls in waste water. Federal Register, Vol. 60, No. 148 August
2, 1995.

21. Tables

                                             Table 1--Pesticides \1\
----------------------------------------------------------------------------------------------------------------
                             Analyte                                  CAS No.     MDL \2\ (ng/L)   ML \3\ (ng/L)
----------------------------------------------------------------------------------------------------------------
Aldrin..........................................................        309-00-2               4              12
alpha-BHC.......................................................        319-84-6               3               9
beta-BHC........................................................        319-85-7               6              18
delta-BHC.......................................................        319-86-8               9              27
gamma-BHC (Lindane).............................................         58-89-9               4              12
alpha-Chlordane \ 4\............................................       5103-71-9              14              42
gamma-Chlordane \ 4\............................................       5103-74-2              14              42
4,4'-DDD........................................................         72-54-8              11              33