SECTION 2: OBJECTIVES The primary objective of the collaborative study is to determine the performance capabilities of the seven 1600 series trace metals methods. A secondary objective is to evaluate, and if appropriate, revise the QC acceptance criteria for data generated by each method. To accomplish these objectives, this study will be conducted in three phases. Phase 1 will focus on pre qualification of laboratories; Phase 2 will focus on collection of natural matrix samples for use in the collaborative study; and Phase 3 will focus on analysis of standard reference materials, reagent water, and natural matrix samples to validate each method of interest in applicable sample matrices. Specific objectives for each phase are described below in Sections 2.1 through 2.3. Data quality objectives are described in Section 2.4.

2.1 Phase 1 Objectives  Laboratory Qualification and Selection The objective of Phase 1 is to ensure that laboratories participating in the collaborative study are familiar with the methods being validated and capable of demonstrating acceptable performance prior to actual implementation of the collaborative study design. Ideally, a full collaborative study on each of the seven Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A 1 Guidelines for Selection and Validation of US EPA's Measurement Methods, U. S. EPA Office of Acid Deposition, Environmental Monitoring and Quality Assurance ( OADEMQA), Office of Research and Development, U. S. Environmental Protection Agency, August 1987 DRAFT.

2 " Report of the Committee on Collaborative Interlaboratory Studies," J. Assoc. Offic. Anal. Chem., 67, ( 2), 1984 3 ASTM Standard D2777 94, " Standard Practice for Determination of Precision and Bias of Methods of Committee D 19 on Water," 11.01, Water ( 1) Annual Book of ASTM Standards, American Society of Testing and Materials, Philadelphia, PA 19103.

A 6 Draft  December 2000 methods should yield a minimum of six complete and useable datasets. 1,2,3 To ensure a useable number of data sets, an objective of Phase 1 is to identify at least nine qualified laboratories that are interested in, and capable of, validating each method in each of the five matrices of interest. Due to a variety of factors, such as instrument limitations, and scheduling constraints, it is unlikely that nine laboratories will be capable of validating all seven methods in each matrix of interest. Therefore, individual laboratories will be allowed to select specific methods that they wish to validate, and allowed to perform analyses on either the ambient and effluent matrices or the marine matrices, or both. The following steps will be taken to ensure that the laboratories selected to take part in the study are qualified to perform trace metals analyses by the methods they select to validate.

2.1.1 Method Blank Analysis Results Each laboratory must submit results from a method blank analysis for each method they are interested in performing. The blanks must be performed according to the method procedures and must be performed specifically for this study. Blank analysis results will be submitted with the laboratory's bid and will be used to identify contamination levels at the laboratory.

2.1.2 Method Detection Limit Studies Each laboratory will be required to submit MDL study results for each method they are interested in performing. The MDL study results will be used to demonstrate the laboratory's ability to perform the method effectively. The MDL study ideally will be conducted in response to this study. However, results from MDL studies for the relevant methods conducted within the past year also will be acceptable. EAD will evaluate MDL study results as part of its identification of qualified laboratories.

MDL studies on reagent water, ambient water, or effluent will be required for laboratories interested in validating method performance in ambient water and effluent matrices. MDL studies on marine water will be required for laboratories interested in validating method performance in marine matrices. Results of the Interlaboratory Study of EPA Method 1638 Appendix A Draft  December 2000 A 7 2.1.3 Provision of Time for Gaining Familiarity with the Methods Because the primary purpose of the collaborative study is to determine the performance capabilities of each method, it is important that laboratories participating in the study be familiar with method requirements and procedures. It is not necessary, however, for each laboratory to have extensive experience with each method. Rather, laboratories participating in the study should have experience that is representative of the federal, state, local, and private laboratories that subsequently will use the method. To achieve this objective, laboratories will be provided with a period of 21  30 days, depending on scheduling constraints, to perform the required MDL studies and blank analyses. This period provides laboratories that have little to no experience with the method with sufficient time to review their methods of choice and perform any preliminary analyses necessary to become familiar with the requirements and procedures.

2.2 Phase 2 Objectives  Sample Collection The objective of Phase 2 is to collect appropriate, uncontaminated natural matrix samples for use in the round robin study. In order to ensure that the samples collected are appropriate for use in a collaborative study, the following secondary objectives will be pursued in this phase:

2.2.1 Collect Samples that Represent Multiple Matrices All seven 1600 series methods are believed to be applicable to ambient water and effluent samples. Four of the methods   Methods 1631, 1632, 1637, and 1640   also are believed to be applicable to marine samples. In addition, reagent water will be analyzed for all methods to establish a baseline characterization of the precision and bias of the methods. Therefore, an objective of Phase 2 is to collect or prepare ambient water, effluent, marine water, and reagent water samples.

2.2.2 Minimize Contamination To control variability among results and to ensure that trace metals detected in the study are not the result of contamination during sampling, it is critical that contamination be strictly controlled during implementation of Phase 2. Therefore, Phase 2 sampling activities and preparation of sampling equipment and bottles will be conducted in accordance with the procedures described in EPA Method 1669: Sampling Ambient Water for Trace Metals at EPA Water Quality Criteria Levels ( EPA 821 R 96 008, July 1996) and in accordance with Sections 4.2.1  4.2.3 of this study plan. In addition, field blanks will be collected with each group of samples and will be analyzed by a referee laboratory to verify that the samples are free from contamination.

2.2.3 Ensure Homogeneity and Characterize Stability Samples used in the collaborative study should be homogeneous in the form and amount/ volume to be tested. All participant laboratories will receive the same sample volumes. The referee laboratory( ies) will agitate the field carboys when creating test samples in an attempt to ensure homogeneity among the samples. The referee laboratory( ies) also will analyze all sample types by all methods over a time period Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A 4 Youden, W. J. and E. H. Steiner, 1975. Statistical Manual of the Association of Official Analytical Chemists, AOAC, 1111 North 19th Street, Suite 210, Arlington, VA 22209 A 8 Draft  December 2000 equivalent to that covering the study, or at the conclusion of the study, to assure stability of the test samples.

2.2.4 Collect Filtered and Unfiltered Samples To verify that each method is applicable to analysis of total recoverable metals and to dissolved metals, an unfiltered aliquot of effluent, marine, and reagent water sample matrices will be collected for subsequent total recoverable metals determinations, and a filtered aliquot of ambient water, effluent, and marine matrices will be collected for dissolved metals determinations.

2.2.5 Collect Samples that Represent Multiple Concentration Ranges To the extent feasible, an objective of Phase 2 is to collect samples that represent the concentration ranges of interest. Specifically, the samples collected should represent levels that are typical of the matrices to which the methods will be applied and of the anticipated regulatory action levels. Regulatory action levels will typically be equal to the WQC levels, the minimum levels ( MLs) specified in the method, or the technology based permitting levels. In general, WQC levels are above both the MDL and the ML, concentrations found in most ambient waters are near the MDL or ML, and concentrations found in effluents are near the ML or the technology based permitting level.

Therefore, EAD believes that a combination of ambient samples and effluent samples will adequately represent the concentration ranges of interest. Collection and subsequent analysis of marine samples by some of the methods may provide additional concentration ranges for those methods applicable to marine water matrices. Finally, the reagent water samples prepared for this study will be spiked at three concentrations across the working range of the methods to characterize method performance and confirm the linear response of the methods. To ensure that natural matrix samples collected are within appropriate concentration ranges, EAD also will spike all of the natural matrix samples as necessary to achieve the desired range( s).

2.2.6 Collect Samples to Allow Evaluation of Intralaboratory Precision To enable EPA to evaluate intralaboratory precision, but preclude laboratories from anticipating results of true replicate samples, a pair of samples will be generated for each of the six matrices in the study according to guidelines developed by Youden. 4 Results from analysis of these samples will be used to generate within laboratory precision estimates. In this study, two batches of spiked samples will be generated for each of the natural matrices. Each laboratory in the study will receive one sample from each batch ( a sample pair) for each method they will be performing and each matrix they will be analyzing. EAD will prepare six batches of samples for the reagent water matrix   two batches for each of the three concentrations across the working range of the Results of the Interlaboratory Study of EPA Method 1638 Appendix A Draft  December 2000 A 9 methods. Each laboratory in the study will receive three pairs of reagent water samples for each method they will be performing.

2.3 Phase 3 Objectives  Method Performance Evaluation The objective of Phase 3 is to evaluate the performance of the seven 1600 series trace metals in multiple laboratories. In previous, single laboratory studies, MDLs, MLs, and QC acceptance criteria were established for each method. Further method optimization is not the goal of this study. The objective of the round robin study is to provide a realistic estimate of the attributes of each method, particularly the systematic and random deviations, to be expected when the method is used in actual practice. A secondary objective is to evaluate the QC acceptance criteria established in the draft methods. If appropriate, results from Phase 3 will be used to modify these acceptance criteria.

Because this study will be used to evaluate method performance under routine laboratory conditions, laboratories will be prohibited from performing multiple analyses to improve recoveries. Laboratories will, however, be allowed to implement corrective action and reanalysis for QC failures that are attributable to analyst error, such as incorrect spiking levels, or to instrument failure. In addition, many methods for trace metals require replicate injections into the instrument. Such replicate injections will be allowed, but in such cases, laboratories participating in the study will be required to identify the instrument on which replicate injections were made, and to report the calculation procedures employed by the instrument to report sample concentrations. For example, some instruments may be programmed to average results of multiple background determinations and subtract that average from the results of replicate sample analyses. Other instruments may be programmed to subtract a single background determination from the average of replicate sample analyses.

To meet the objectives of Phase 3, laboratories in the study will analyze pairs of real world samples, representing up to five different matrices, pairs of reagent water samples, representing three concentrations across the working range of the methods, and up to two standard reference materials ( SRMs). The five real world matrices include filtered ambient water, unfiltered and filtered effluent, and unfiltered and filtered marine water. Laboratories will analyze the following:

C A pair of effluent water samples and three pairs of reagent water samples for total recoverable metals using Methods 1631, 1632, 1636, 1637, 1638, 1639, and 1640 C A pair of ambient water samples and a pair of effluent water samples for dissolved metals using Methods 1631, 1632, 1636, 1637, 1638, 1639, and 1640 C A pair of marine water samples for dissolved and total recoverable metals using Methods 1631, 1632, 1637, and 1640 Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A A 10 Draft  December 2000 2.4 Data Quality Objectives for Phases 1 through 3 In addition to the overall objectives described above, EAD has three principle data quality objectives ( DQOs) for this study:

1. All samples and data produced under this study must be generated according to the analytical and QA/ QC procedures defined in the relevant method. Alternatively, the data must be the result of preapproved and documented changes to these procedures. This will allow EAD to use the results of the round robin study to identify the need for further revision of the method.

2. All data produced under this phase of the study must be capable of being verified by an independent person reviewing the analytical data package.

3. The MDLs determined in Phase 1 of this study must be within a factor of five of the level spiked to ensure that MDLs determined in the study are neither overstated nor understated.

To meet study DQOs, the laboratories will be required to have a comprehensive QA program in place and operating throughout the study. This will ensure that the data produced are of appropriate and documented quality.

During Phase 1 of the study, the laboratories will be required to follow all QC procedures defined in the methods they are interested in validating, with the following exceptions:

C Demonstration of initial and ongoing precision and recovery will not be required during Phase 1.

C Performance of matrix spike ( MS) and matrix spike duplicate ( MSD) analyses will not be required during Phase 1.

C Analysis of field blanks and equipment blanks will not be required during Phase 1.

C Instrument calibration must be performed at a range that will encompass the minimum level ( ML) specified in the method during Phase 1.

During Phases 2 and 3 of the study, laboratories will be required to follow all QC procedures defined in the methods. No exceptions will be allowed. All analyses performed in each phase of the study must be performed on a calibrated instrument, and calibration verification must be performed at the frequency specified in each method.

SECTION 3: STUDY MANAGEMENT The study described in this document will be managed by AMS. Day to day management and coordination of study activities will be performed by the contractor operated Sample Control Center ( SCC) under AMS guidance. Collection of samples under Phase 2 of the study will be performed by either SCC or a referee laboratory not participating in Phase 3 of the study. This referee laboratory will have extensive experience Results of the Interlaboratory Study of EPA Method 1638 Appendix A Draft  December 2000 A 11 with the procedures used in the methods and may be funded through one of EAD's existing contracts. If a single laboratory with extensive experience using all seven methods is not available to support this study, more than one referee laboratory will be sought, such that one referee laboratory is available for each method.

The total number of laboratories participating in Phase 3 of this study will depend upon laboratory capability ( as determined in Phase 1) and availability, cost, and scheduling constraints. Laboratories participating in Phase 3 of this study may include commercial laboratories, academic laboratories, state laboratories, EPA laboratories, and/ or municipal laboratories. To ensure that study schedules are maintained, EPA will issue a small purchase order or will issue a delivery order to one or more of its current contract laboratories following a competitive bidding process. The awarded laboratory( ies) and their subcontractors must fulfill the Phase 1 prequalification requirements as part of their bidding process. This approach will be used to ensure that appropriate controls on study schedule and data quality can be imposed. These controls include the required Phase 1 method familiarization and pre qualification requirements, explicit schedule and performance requirements, and the imposition of liquidated damages for failing to follow study requirements and/ or meet study schedules. Additional laboratory support will be sought from EPA Regional laboratories, state laboratories, and/ or municipal laboratories on a voluntary basis. If necessary, and if feasible, these government laboratories may be reimbursed for their costs of participating in the study.

SCC will coordinate sample collection and laboratory analysis, and will receive and validate all analytical data and perform statistical analyses. AMS will draw conclusions from the results and produce a report providing the results of the study. If appropriate, AMS will revise one or more methods evaluated in the study as necessary to reflect study findings. AMS also will share data and results with all interested parties upon request.

SECTION 4: TECHNICAL APPROACH 4.1 Phase 1 Technical Approach Phase 1 entails the evaluation of laboratory capability based on blank analysis results and MDL studies.

4.1.1 Method Blank Analysis Each laboratory will be required to submit results from the analysis of a laboratory ( method) blank for each method they are interested in performing. These blank determinations will be used to determine if each laboratory is capable of maintaining contamination within acceptable levels for this study. EPA will evaluate each laboratory's blank results against historical values produced with the method and with other laboratories' results. Laboratories submitting blanks with unacceptable levels may have the opportunity to analyze additional blanks to reduce the uncertainty regarding their capacity to produce acceptable data at low concentrations. Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A A 12 Draft  December 2000 4.1.2 Method Detection Limit Study Each laboratory must submit results of an MDL study for each method they are interested in performing. The MDL study must be performed in accordance with the procedure described in Federal Register Vol. 49 No. 209, Friday, October 26, 1984, Appendix B to Part 136  Definition and Procedure for the Determination of the Method Detection Limit  Revision 1.11. This procedure involves the analysis of at least seven replicate samples that are known to contain the target analyte( s) at a concentration of one to five times the estimated MDL.

Acceptance of Method Detection Limit Studies Performed Within the Past Year. Laboratories that have performed MDL studies within the past year for one or more of the seven targeted methods are permitted to submit those results instead of performing new MDL studies. However, if changes that could affect method performance have occurred at the laboratory since an MDL study was performed, those MDL study results cannot be used. Acceptable MDL study matrices for laboratories interested in performing analyses on ambient and effluent matrices include reagent water, ambient water, and effluent. Acceptable MDL study matrices for laboratories interested in performing analyses on marine matrices are limited to marine water.

Procedure for Method Detection Limit Studies Performed for this Study. For each method, laboratories interested in performing analyses on ambient and effluent matrices will spike reagent water, ambient water, or effluent with the analyte( s) listed in the method to produce a synthetic sample that can be divided into at least seven replicates. Laboratories interested in performing analyses on marine samples will spike marine samples with the analyte( s) listed in the method to produce a synthetic sample that can be divided into at least seven replicates.

To ensure that the laboratory is spiking at the appropriate level, it is recommended that the laboratory follow the two aliquot test described in Section 4b of the MDL procedure. If these measurements indicate that a sample concentration is in the desired range for determination of the MDL, a laboratory may proceed with five additional aliquots for a total of seven aliquots. All seven measurements will be used for calculation of the MDL. If the first two measurements indicate that the sample concentration is not in the correct range, the laboratory will be required to repeat Section 4b ( analysis of two spiked aliquots) until the desired spike level is achieved. Application of the two aliquot test is recommended to minimize the possibility of repeating the MDL study in order to obtain an MDL that is within a factor of five of the level spiked.

If a laboratory's MDL resulting from its study is not within a factor of five of the level spiked, then the spiking, measurement, and calculation processes will be repeated until the measured MDL is within a factor of five, as given in the MDL procedure. If the laboratory obtains non detect results during their MDL study, that laboratory must increase the spike level and repeat the test. The objective of these requirements is to ensure that MDLs resulting from the study are not artificially high or low due to inappropriate spiking levels. Results of the Interlaboratory Study of EPA Method 1638 Appendix A Draft  December 2000 A 13 The analytical portion of each MDL study will be performed in accordance with the procedures described in the applicable 1600 series method. Each laboratory will submit MDL study results in an MDL summary table that groups data under the following categories:

C Spiked concentration in each of the seven replicates C Measured concentration in each of the seven replicates C The mean of the seven measured concentrations C The standard deviation of these measurements C The Student's t value used C The calculated MDL for the technique Other reporting requirements are detailed in Section 5 of this study plan.

4.2 Phase 2 Technical Approach Samples will be collected with bottles and equipment that have been pre cleaned by a laboratory experienced in the analysis of trace metals at ambient water quality criteria levels. Samples will be collected by EAD and SCC staff or by the selected referee laboratory( ies) using procedures detailed in Method 1669 for ambient and marine samples or procedures based on the principles outlined in Method 1669 as adapted to effluent sampling.

The sampling team will collect sufficient volume of each real world matrix to allow for distribution of filtered and unfiltered sample pairs to each laboratory, to allow for analysis of MS and MSD samples, and to provide extra volume in case of sample breakage, lost shipments, or other unforeseen problems. The referee laboratory( ies) will prepare sufficient unfiltered reagent water volume to allow for distribution of three sample pairs per method to each laboratory and provide extra volume in case of sample breakage, lost shipments, or other unforeseen problems.

In addition, the sampling team will collect separate aliquots for analysis of trivalent and hexavalent chromium. The field team will follow the procedures outlined in Method 1669 for preservation of trivalent and hexavalent chromium to preserve these parameters immediately upon collection. To minimize sample handling in the field, aliquots for all other parameters will be preserved immediately upon receipt by the referee laboratory.

All samples will be homogenized and divided into batches under controlled clean room conditions by the referee laboratory( ies). The referee laboratory( ies) will analyze random samples to ensure that concentration levels found in the natural matrices are appropriate for this study. The referee laboratory( ies) will report results of these analyses to SCC for review. If problems are identified, SCC will notify EAD to Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A A 14 Draft  December 2000 discuss and implement appropriate corrective actions, including resampling, additional homogenization, sample spiking, sample dilution, and/ or other procedures. In addition, the referee laboratory( ies) will reanalyze samples during the study period or at the conclusion of the study to verify the stability of test samples. These results will be reported to SCC for review. Specific activities associated with the sample collection and preparation tasks are described below.

4.2.1 Equipment Cleaning and Preparation Prior to commencement of field sampling activities, sample bottles and necessary sampling equipment will be obtained from an experienced cleaning facility. The cleaning facility will utilize the guidance stated in Method 1669 and the associated trace metals analysis methods to thoroughly clean, store, and ship all required equipment to organization responsible for sample collection and will implement QC protocols necessary to verify and certify that the bottles and sampling equipment are free of any target metals at the levels of interest in this study.

4.2.2 Field Sampling A total of five real world sample matrices will be collected in the field: filtered ambient water samples; unfiltered effluent samples, filtered effluent samples; unfiltered marine samples, and filtered marine samples. All sampling activities to be performed under this study will be performed by SCC or referee laboratory staff who have observed and been trained in the collection of samples using the " clean hands/ dirty hands" techniques described in Method 1669, as adapted for effluent sampling where necessary. These techniques entail using two sampling team members ( designated " clean hands" and " dirty hands") for different aspects of the sample collection and filtering tasks to minimize contamination. If feasible, a third individual will be responsible for performing all sample documentation activities. The sampling team will process trivalent and hexavalent chromium samples in a clean, contaminant free area.

To simplify documentation, specific sample numbers will be pre assigned to each sampling point and bottle prior to collection. The number of each sample bottle will be documented and associated with the preassigned sample number in a field log prior to commencement of sampling activities. The pre assigned sample number will be pre recorded on the outside storage bag used to store the sample bottle. Once in the field, the " dirty hands" team member will read the sample number printed on the outside bag to the documentation team member. After " clean hands" has removed the sample bottle from the inside storage bag, " clean hands" will read the bottle number to the documentation team member. In this way, the documentation team member can minimize actual field transcription yet verify that the appropriate bottle is being utilized. The team member will record the time that the sample is collected, field conditions, and any problems or other issues noted by the " clean hands/ dirty hands" team during collection.

4.2.3 Sample Filtration, Sample Preservation, and Sample Shipment Filtration: Trace metals samples, including mercury samples, will be filtered in the field according to the filtration procedure described in Section 8.3 of Method 1669. In brief, samples will be collected using a peristaltic pump and new, cleaned tubing that terminates in a 0.45 µ m capsule filter. The sampling team will assemble the filtration system inside a contaminant free glove bag, and flush the system with Results of the Interlaboratory Study of EPA Method 1638 Appendix A Draft  December 2000 A 15 approximately 200 mL of reagent water. After the system is flushed, the team will collect a blank sample, and then collect in carboys the volume needed for the filtered trace metals samples. The capsule filter will be replaced after each carboy is filled, and the sampling team will flush the system and take a blank sample before samples are collected using a new filter.

Preservation: The techniques described in Sections 8.4.4 and 8.4.5 of Method 1669 will be used to preserve aliquots for trivalent and hexavalent chromium. Briefly, the sampling team will preserve trivalent chromium by pipetting 1 mL of chromium ( III) extraction solution to a 100 mL sample aliquot and shaking the sample. The team will vacuum filter the resulting precipitate through a 0.4 µ m pretreated polycarbonate filter membrane and rinse the filter holder. The filter will be folded and transferred to a fluoropolymer vial with ultrapure nitric acid. The sampling team will preserve hexavalent chromium by pipetting 1 mL of NaOH to a 125 mL sample aliquot.

Shipping: All samples will be shipped to the referee laboratory( ies) via overnight courier. Immediately after sample shipment ( i. e., as soon as samples are in the custody of the carrier), the sampling team will call SCC and provide information on the shipment, including sample numbers, numbers of coolers, and courier and airbill number. SCC will notify the referee laboratory when samples will arrive.

4.2.4 Determination of Field Sample Concentrations SCC will ship carboys of field samples to the referee laboratory for homogenization and generation of individual samples for analysis by the participant laboratories. SCC will ship multiple carboys for the following five sample matrix types to the referee laboratory: filtered ambient water, unfiltered effluent, filtered effluent, unfiltered marine water, and filtered marine water. The referee laboratory will analyze volume from a representative carboy for each of the five matrix types to ensure that concentration levels found in the natural matrices are appropriate for this study. To ensure homogeneity in each carboy sampled, the referee laboratory will collect samples from the field carboys while continually agitating the carboys.

The referee laboratory shall analyze one filtered ambient water sample, one unfiltered effluent sample, and one filtered effluent sample per method using Methods 1631, 1632, 1636, 1637, 1638, 1639, and 1640. The referee laboratory also will analyze one unfiltered marine water sample and one filtered marine water sample per method for Methods 1631, 1632, 1637, and 1640.

The referee laboratory shall report the results of these analyses to SCC for review. If problems are identified, SCC will notify EAD to discuss and implement appropriate corrective actions, including resampling, sample spiking, sample dilution, and/ or other procedures. EAD and/ or SCC will inform the referee laboratory of any actions needed before volume in the field carboys is aliquoted into sample pairs.

4.2.5 Generation of Sample Pairs and Homogenization of Samples Sample pairs prepared according to Youden's guidance will be generated for each real world matrix by splitting the volume collected for each matrix and spiking ( as necessary) each of the two split sample Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A A 16 Draft  December 2000 volumes with target analytes. Prior to aliquoting test samples from the field carboys, the reference laboratory( ies) will split the carboys for each matrix into two batches. The referee laboratory( ies) will spike each batch with target analytes in the desired concentration range. All samples within a batch will therefore contain identical levels of target analytes. For each real world matrix, one sample from each batch will be sent to each laboratory as a pair.

In addition to generating two batches of samples for each real world matrix, the referee laboratory( ies) also will prepare six batches of reagent water samples, which will be used to create pairs of reagent water samples in three concentrations. The referee laboratory will split the six reagent water batches into three sets of two. Reagent water in the sets will be spiked with the analytes of interest at three different concentrations across the working range of the methods to yield one set ( two batches) of reagent water for each of the three concentrations. For each set, the referee laboratory( ies) will spike each batch with target analytes in the desired concentration range. All samples within a batch will therefore contain identical levels of target analytes. For each set ( concentration) of reagent water, one sample from each batch will be sent to each laboratory as a pair, yielding three pairs of reagent water samples.

To ensure homogeneity of the samples in each batch of real world matrices and reagent water, the referee laboratory( ies) will aliquot samples from the carboys while continually agitating the carboys in an attempt to ensure homogeneity. After the referee laboratory( ies) aliquot all of the test samples from the field carboys, the laboratory( ies) will analyze randomly selected samples across each of the sample series prepared for the study to assure among sample homogeneity.

The referee laboratory( ies) will test samples for homogeneity in a clean room, using equipment that has been cleaned according to Method 1669 and demonstrated to be free from contamination. The referee laboratory( ies) will generate acceptable equipment blanks and laboratory blanks to demonstrate that the facility was free of contamination during the homogeneity testing.

The referee laboratory( ies) will report the results of their subsampling analyses to SCC. SCC will review the data, consult with EPA, and issue further directions to the referee laboratory regarding distribution of samples to the study participants. If the data indicate that samples are not homogenous, SCC will issue corrective action instructions to the referee laboratory( ies).

4.2.6 Stability Analysis The referee laboratory( ies) also will analyze all sample types by all methods to assure stability of the test samples.

To assess stability of the test samples, the referee laboratory( ies) will analyze samples from each matrix and concentration using each analytical method over a time period equivalent to that covering the study. Specifically, the referee laboratory( ies) will analyze at least one filtered ambient water sample, at least one unfiltered effluent sample, at least one filtered effluent sample, and at least one reagent water sample at each concentration using Methods 1631, 1632, 1636, 1637, 1638, 1639, and 1640. The referee laboratory( ies) will analyze at least one unfiltered marine water sample and at least one filtered marine Results of the Interlaboratory Study of EPA Method 1638 Appendix A Draft  December 2000 A 17 water sample per method for Methods 1631, 1632, 1637, and 1640. The referee laboratory will submit the results of these analyses to SCC for evaluation and comparison with the pre study results.

4.3 Phase 3 Technical Approach Phase 3 entails the use of 1600 series methods at multiple laboratories to analyze real world samples, reagent water samples, and standard reference materials for trace metals. AMS will use the results of these analyses to assess the performance of each method under routine conditions. As noted in Phase 1, each laboratory may be approved to perform one, several, or all of the 1600 series methods. Laboratories may elect to analyze a combination of ambient water, effluent, and reagent water samples and/ or marine water samples for each of the methods they are approved to perform. Laboratories will not be allowed to analyze ambient water, effluent, or reagent water samples alone; these matrices must be analyzed as a set.

The general approach to the round robin study entails the following analyses at each laboratory:

C Qualified round robin laboratories will analyze a pair of filtered ambient water samples for dissolved metals using Methods 1631, 1632, 1636, 1637, 1638, 1639, and/ or 1640.

C Qualified round robin laboratories will analyze a pair of filtered effluent water samples for dissolved metals and a pair of unfiltered effluent water samples for total recoverable metals using Methods 1631, 1632, 1636, 1637, 1638, 1639, and/ or 1640.

C Qualified round robin laboratories will analyze three pairs of reagent water samples for total recoverable metals using Methods 1631, 1632, 1636, 1637, 1638, 1639, and/ or 1640.

C Qualified round robin laboratories will analyze a pair of filtered marine water samples for dissolved metals and a pair of unfiltered marine water samples for total recoverable metals using Methods 1631, 1632, 1637 and/ or 1640. Note: To prevent loss of sensitivity, laboratories analyzing marine water samples using Method 1631 will be required to modify the procedure at Section 11.1.1. Laboratories will add 0.2 mL of bromine monochloride ( BrCl) to 100 mL of sample instead of the 0.5 to 5 mL of BrCl required by the method.

C Qualified laboratories performing analyses on ambient and effluent samples will periodically analyze an SRM for ambient water. Qualified laboratories performing analyses on marine water samples will periodically analyze an SRM for marine water. If EAD funding permits, EPA will purchase the SRMs for the study and distribute them to the participant laboratories with the test samples. If this plan is cost prohibitive, EAD will require the participant laboratories to purchase specific SRMs identified by EAD.

The following specific requirements apply to analyses by each method: Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A A 18 Draft  December 2000 C With the exception of the modification to Method 1631 for marine water samples noted above, all laboratories must follow the methods exactly. Any deviation, such as the necessity to substitute reagents, apparatus, or instruments, must be recorded at the time and reported.

C All laboratories must follow all QC procedures and the analytical sequence defined in the methods they are performing.

C Each portion of the sample pair will be analyzed once, as replication defeats the purpose of the design, except where the method requires replicate injections ( see next bullet).

C If analytical results appear unreasonable, laboratories should investigate possible causes immediately, first by checking for transcription and calculation mistakes, and then by reanalysis. Although laboratories will be prohibited from performing multiple analyses to improve recoveries, they will be allowed to implement corrective action and reanalysis for QC failures that are attributable to analyst error, such as incorrect spiking levels, or to instrument failure. In addition, many methods for trace metals require replicate injections into the instrument. Such replicate injections will be allowed, but in such cases, laboratories participating in the study will be required to identify the instrument on which such replicate injections were made, and to report the calculation procedures employed by the instrument to report sample concentrations. For example, some instruments may be programmed to average results of multiple background determinations and subtract that average from the results of replicate sample analyses. Other instruments may be programmed to subtract a single background determination from the average of replicate sample analyses.

C All laboratories analyzing the set of ambient water, effluent, and reagent water samples must prepare and analyze MS and MSD samples for one member of each of the effluent pairs ( one MS/ MSD for filtered effluent and one MS/ MSD for unfiltered effluent). All laboratories analyzing marine water samples must prepare and analyze MS and MSD samples for one member of each of the marine water pairs ( one MS/ MSD for filtered marine water and one MS/ MSD for unfiltered marine water). To control variability in the study, SCC will designate which samples should be used for MS/ MSD analysis and the concentrations that should be spiked into each sample.

C All laboratories will analyze materials within sample holding times.

C All laboratories must conduct exactly the number of determinations stated in the instructions. Any other number complicates the statistical analysis.

C All laboratories must report individual values, including blanks. Laboratories will not average or do other data manipulations unless required by a method's instructions. When results are below the MDL, laboratories should report the actual calculated result, regardless of its value. Results of the Interlaboratory Study of EPA Method 1638 Appendix A Draft  December 2000 A 19 SECTION 5: DATA REPORTING AND EVALUATION The laboratories will be required to submit both summary level and raw data in hardcopy format. Summary level data also must be provided in electronic format. The laboratories also will be required to submit detailed explanations of any approved modifications to the analytical techniques specified in the methods and used in this study. Specific reporting requirements are or will be detailed in each laboratory's analytical statement of work and are summarized below.

Upon the receipt of a laboratory data package, SCC will review the data to ensure that they were generated in accordance with the required procedures. Laboratory comments and suggestions also will be used to identify further revisions that should be made to the methods.

The following rules should be followed in reporting results:

1. Quantitative results above or at the MDL  report value 2. Quantitative results below the MDL  report value but flag with footnote giving the MDL 3. Nonquantitative results  report as less than the MDL value and state the MDL value 4. The terms " zero," " trace," or " ND ( not detected)" are not to be used 5. Laboratories must report concentrations as F g/ L and report data to three significant figures The laboratory shall report the following data, at a minimum:

1. Summary reports of all analytical results.

2. A list of samples analyzed and a run chronology.

3. Copies of all raw data, including quantitation reports, strip charts, spectra, bench sheets, and laboratory notebooks showing tare and sample weights, sample volumes, and other data that will allow verification of the calculations performed and will allow the final results reported to be traced to the raw data. Each data element shall be clearly identified in the laboratory's data package.

4. A written report that details any problems associated with analysis of the samples. The written report also shall provide comments on the performance of any part of a method.

5. A detailed written description of any modifications to the procedures specified in the methods. Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix A A 20 Draft  December 2000 SECTION 6: LIMITATIONS Size of study: To avoid excessively large confidence limits around the precision ( variance), and bias ( mean recovery) statements, this round robin study should yield a minimum of six complete and useable data sets. Therefore, the number of laboratories participating in a study should be increased sufficiently beyond six to assure a that at least six sets of complete and useable data are available after outliers and non usable data are removed. Participation by a minimum of six laboratories is recommended by ASTM and AOAC.

Assuming a 25% data loss, a minimum of nine laboratories are needed to participate in the study to obtain at least six sets of useable data. Ideally, this study will consist of as many as 15 laboratories, including at least 6 commercial laboratories funded by EPA. EPA funding of commercial laboratories will provide a level of enforceability, helping to ensure timely submission of data. EPA anticipates that government, academic, and utility laboratories will comprise the balance of the participant laboratories. These laboratories are anticipated to participate voluntarily or through funding by interested organizations, such as ASTM and EPRI.

Normally, it is desirable to allow participation by only one analyst in each laboratory to avoid potential cross talk and sharing of reagents, standards, or instruments within a laboratory. It may be impossible to obtain nine qualified participant laboratories for this study, so it may be necessary to allow multiple analysts per laboratory. If such a contingency is necessary, safeguards will be developed to assure the independence of the two analytical processes, including separate reagents, instrumentation, sample preparation, and analyses.

Effluent variability: Effluent matrices vary, particularly pretreated effluents ( indirect dischargers) and treated effluents ( direct dischargers). Effluent samples for this study will be collected from the treated effluent stream at a well designed, well operated, best available technology publicly owned treatment works. Untreated effluent will not be collected or analyzed because the matrix may overload the analytical methods and will not be representative of any other untreated effluent, limiting the usefulness of any analytical results. Draft  December 2000 Appendix B Data Submitted in the Interlaboratory Method 1638 Validation Study Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix B B 1 Draft  December 2000 Table 1: Phase 2, Sample Stability Results Analyte Matrix Expected ( µ g/ L) Initial ( 1) ( µ g/ L) Initial ( 2) ( µ g/ L) Average % Recovery Final ( 1) ( µ g/ L) Final ( 2) ( µ g/ L) Average % Recover y % Recovery RPD Antimony ML = 0.2 Reagent Pair 1 0.0000 0.0081 0.0015   0.0234  0.0285

Reagent Pair 2 1.0000 0.9680 0.9664 97 0.9081 0.9116 91 6

Reagent Pair 3 5.0000 4.8800 4.8740 98 4.7280 4.7130 94 3

Reagent Pair 4 20.0000 19.7400 19.1513 97 19.0600 19.0100 95 2

* Reagent Pair 5 ( low) 0.1000 0.0831   0.0072

* Reagent Pair 5 ( high) 0.1200 0.1073   0.0723

* Freshwater Pair 1 0.1241 0.1526 0.1349  0.1014 0.1036

Freshwater Pair 2 ( low) 0.2041 0.2002  98 0.1650  81 19

Freshwater Pair 2 ( high) 0.2441 0.2346  96 0.2009  82 15

Freshwater Pair 3 ( low) 0.4041 0.3866  96 0.3603  89 7

Freshwater Pair 3 ( high) 0.5041 0.4695  93 0.4550  90 3

Freshwater Pair 4 ( low) 0.8041 0.7768  97 0.7366  92 5

Freshwater Pair 4 ( high) 1.0041 0.9612  96 0.9464  94 2

Unfiltered Effluent 10.0000 9.5000 9.556 95 9.399 9.375 94 1

Filtered Effluent 1.0000 1.0210 1.0350 103 0.9807 0.9850 98 4

Cadmium ML  0.2 µ g/ L Reagent Pair 1 0.0000  0.0048  0.0041   0.0021  0.0029

* Reagent Pair 2 0.1000 0.0946 0.0935  0.0973 0.0958

Reagent Pair 3 1.0000 0.9793 0.9561 97 0.9637 0.9689 97 0

Reagent Pair 4 10.0000 9.5820 9.6810 96 9.5710 9.5830 96 1

* Reagent Pair 5 ( low) 0.0500 0.0431   0.0502

* Reagent Pair 5 ( high) 0.0600 0.0508   0.0567

Freshwater Pair 1 0.2500 0.2439 0.2393 97 0.2419 0.2418 97 0+

Freshwater Pair 2 0.0000  0.0081   0.0016

* Freshwater Pair 3 ( low) 0.0400 0.0321   0.0398

* Freshwater Pair 3 ( high) 0.0500 0.0412   0.0492

* Freshwater Pair 4 ( low) 0.1200 0.1069   0.1163

* Freshwater Pair 4 ( high) 0.1400 0.1325   0.1369    Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix B Table 1: Phase 2, Sample Stability Results Analyte Matrix Expected ( µ g/ L) Initial ( 1) ( µ g/ L) Initial ( 2) ( µ g/ L) Average % Recovery Final ( 1) ( µ g/ L) Final ( 2) ( µ g/ L) Average % Recover y % Recovery RPD Draft  December 2000 B 2 Unfiltered Effluent 0.5000 0.5053 0.5086 101 0.4948 0.4972 99 2

Filtered Effluent 0.3000 0.3150 0.3095 104 0.3206 0.3228 107 3+

Copper ML = 0.5 µ g/ L Reagent Pair 1 0.0000 0.0249 0.0186  0.0271 0.0229

Reagent Pair 2 0.5000 0.5383 0.5408 108 0.5118 0.5186 103 5

Reagent Pair 3 2.0000 2.1440 2.1060 106 2.0450 2.0260 102 4

Reagent Pair 4 20.0000 20.5400 20.6700 103 20.2300 20.0400 101 2

* Reagent Pair 5 ( low) 0.2000 0.2000   0.2134

* Reagent Pair 5 ( high) 0.2400 0.2700   0.2552

Freshwater Pair 1 1.0300 1.2080 1.1680 115 1.1290 1.0950 108 7

Freshwater Pair 2 ( low) 1.5300 1.5975  104 1.5600  102 2

Freshwater Pair 2 ( high) 1.7300 1.7596  102 1.735  100 1

Freshwater Pair 3 ( low) 2.5300 2.5467  101 2.519  100 1

Freshwater Pair 3 ( high) 3.0300 3.0903  102 3.092  102 0+

Freshwater Pair 4 ( low) 4.5300 4.5065  99 4.449  98 1

Freshwater Pair 4 ( high) 5.0300 4.9809  99 4.937  98 1

Unfiltered Effluent 15.1000 15.8600 15.5000 104 14.5600 14.4200 96 8

Filtered Effluent 13.8000 14.6300 14.3500 105 13.3100 13.3700 97 8

Lead ML = 0.05 µ g/ L Reagent Pair 1 0.0000  0.0926  0.0915   0.0030  0.0048

Reagent Pair 2 0.1000 0.0874 0.0939 91 0.0898 0.0917 91 0+

Reagent Pair 3 0.5000 0.4015 0.4029 80 0.4799 0.4775 96 17+

Reagent Pair 4 5.0000 4.9610 4.944 99 4.9080 4.856 98 1

* Reagent Pair 5 ( low) 0.0300 0.0236   0.0327

* Reagent Pair 5 ( high) 0.0360 0.0341   0.0365

Freshwater Pair 1 0.2000 0.1997 0.2014 100 0.2047 0.2032 102 2+

* Freshwater Pair 2 0.0128 0.0205 0.0206  0.0229 0.0214

Freshwater Pair 3 ( low) 0.0528 0.0559  106 0.0577  109 3+

Freshwater Pair 3 ( high) 0.0628 0.0679  108 0.0676  108 0 Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix B Table 1: Phase 2, Sample Stability Results Analyte Matrix Expected ( µ g/ L) Initial ( 1) ( µ g/ L) Initial ( 2) ( µ g/ L) Average % Recovery Final ( 1) ( µ g/ L) Final ( 2) ( µ g/ L) Average % Recover y % Recovery RPD B 3 Draft  December 2000 Freshwater Pair 4 ( low) 0.3128 0.3105  99 0.2976  95 4

Freshwater Pair 4 ( high) 0.3628 0.3663  101 0.3410  94 7

Unfiltered Effluent 1.0557 0.9966 1.0214 96 1.0260 1.019 97 1+

Filtered Effluent 0.5000 0.4427 0.4448 89 0.5188 0.5249 104 16+

Nickel ML = 0.5 µ g/ L Reagent Pair 1 0.0000 0.0575 0.0544   0.0026  0.0011

Reagent Pair 2 1.0000 1.0830 1.0980 109 1.0310 1.0090 102 7

Reagent Pair 3 10.0000 10.4600 10.2500 104 10.1500 10.1800 102 2

Reagent Pair 4 100.0000 99.6100 99.1500 99 100.4000 99.1600 100 0+

Reagent Pair 5 ( low) 0.5000 0.4887  98 0.4908  98 0+

Reagent Pair 5 ( high) 0.6000 0.5897  98 0.6039  101 2+

Freshwater Pair 1 6.0000 6.1420 6.1450 102 6.0500 6.0460 101 2

* Freshwater Pair 2 0.3100 0.2329 0.2378  0.2906 0.2899

Freshwater Pair 3 ( low) 1.6100 1.4841  92 1.578  98 6+

Freshwater Pair 3 ( high) 1.8100 1.7226  95 1.771  98 3+

Freshwater Pair 4 ( low) 3.3100 3.1507  95 3.171  96 1+

Freshwater Pair 4 ( high) 4.0100 3.8920  97 3.939  98 1+

Unfiltered Effluent 8.0000 7.1960 7.0580 89 7.3110 7.1570 90 1+

Filtered Effluent 7.0000 6.5580 6.3820 92 6.5620 6.5190 93 1+

Selenium ML = 2.0 µ g/ L Reagent Pair 1 0.0000  0.3436  0.3890   0.0003 0.0647

Reagent Pair 2 5.0000 4.6870 4.6990 94 5.0970 5.0704 102 8+

Reagent Pair 3 20.0000 20.2300 19.5700 100 20.5200 20.7600 103 4+

Reagent Pair 4 100.0000 98.8000 99.8200 99 103.5000 104.8000 104 5+

* Reagent Pair 5 ( low) 1.0000 0.7650   1.284

* Reagent Pair 5 ( high) 1.2000 0.8625   1.635

Freshwater Pair 1 4.0000 3.7050 3.7000 93 3.9250 3.9410 98 6+

* Freshwater Pair 2 0.3810 0.0640 0.0876  0.3224 0.2985

* Freshwater Pair 3 ( low) 0.9810 0.6790   0.9400    Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix B Table 1: Phase 2, Sample Stability Results Analyte Matrix Expected ( µ g/ L) Initial ( 1) ( µ g/ L) Initial ( 2) ( µ g/ L) Average % Recovery Final ( 1) ( µ g/ L) Final ( 2) ( µ g/ L) Average % Recover y % Recovery RPD Draft  December 2000 B 4 * Freshwater Pair 3 ( high) 1.1810 0.9591   1.245

* Freshwater Pair 4 ( low) 1.9810 1.7130   2.192

Freshwater Pair 4 ( high) 2.3810 2.0686  87 2.669  112 25

Unfiltered Effluent 6.0000 5.2160 5.3430 88 6.0240 6.0250 100 13+

Filtered Effluent 5.0000 4.4890 4.5590 90 4.9530 5.0250 100 10+

Silver ML = 0.1 µ g/ L Reagent Pair 1 0.0000 0.0050  0.0025   0.0135  0.0236

Reagent Pair 2 0.1000 0.1070 0.1413 124 0.0938 0.0986 96 25

Reagent Pair 3 1.0000 1.0110 1.025 102 1.1020 1.101 110 8+

Reagent Pair 4 10.0000 10.3000 10.56 104 11.2700 11.21 112 7+

* Reagent Pair 5 ( low) 0.0400 0.2161    0.0542

* Reagent Pair 5 ( high) 0.0500 0.2603    0.0107

Freshwater Pair 1 0.2000 0.2666 0.2257 123 0.2107 2.169 107 14

Freshwater Pair 2 0.0000 0.0475 0.0359   0.0592  0.0618

* Freshwater Pair 3 ( low) 0.0700 0.0935    0.0316

* Freshwater Pair 3 ( high) 0.0800 0.1018    0.0219

Freshwater Pair 4 ( low) 0.3000 0.3123  104 0.0800  27 118

Freshwater Pair 4 ( high) 0.3600 0.3851  107 0.0761  21 134

Unfiltered Effluent 2.8800 1.4980 1.4780 52 1.4960 1.5590 53 3+

Filtered Effluent 0.4780 0.4675 0.4721 98 0.4523 0.4613 96 3

Thallium ML = 0.05 µ g/ L Reagent Pair 1 0.0000 0.0064 0.0021   0.0005  0.0008

Reagent Pair 2 0.1000 0.1047 0.1020 103 0.0966 0.0993 98 5

Reagent Pair 3 0.5000 0.5074 0.5109 102 0.4898 0.4925 98 4

Reagent Pair 4 2.0000 2.0530 2.048 103 1.997 1.991 100 3

* Reagent Pair 5 ( low) 0.0400 0.0404   0.0434

Reagent Pair 5 ( high) 0.0500 0.0503  101 0.0521  104 4+

Freshwater Pair 1 0.0600 0.0629 0.0598 102 0.0589 0.0583 98 5

* Freshwater Pair 2 0.0010 0.0006  0.0005  0.0073 0.0067   Results of the Interlaboratory Validation Study of EPA Method 1638 Appendix B Table 1: Phase 2, Sample Stability Results Analyte Matrix Expected ( µ g/ L) Initial ( 1) ( µ g/ L) Initial ( 2) ( µ g/ L) Average % Recovery Final ( 1) ( µ g/ L) Final ( 2) ( µ g/ L) Average % Recover y % Recovery RPD B 5 Draft  December 2000 * Freshwater Pair 3 ( low) 0.0210 0.0170   0.0238

* Freshwater Pair 3 ( high) 0.0240 0.0218   0.0278

Freshwater Pair 4 ( low) 0.1010 0.0993  98 0.0985  98 1

Freshwater Pair 4 ( high) 0.1210 0.1192  99 0.1151  95 3

Unfiltered Effluent 0.9000 0.8872 0.9007 99 0.8347 0.8283 92 7+

Filtered Effluent 0.2000 0.1863 0.1972 96 0.1804 0.1818 91 6

Zinc ML = 1.0 µ g/ L Reagent Pair 1 0.0000  0.0255  0.0037   0.1395  0.1686

* Reagent Pair 2 0.5000 0.4474 0.4703  0.0000 0.3390

Reagent Pair 3 5.0000 4.9600 4.9190 99 4.8190 4.8310 97 2

Reagent Pair 4 50.0000 49.3000 50.3500 100 49.6800 50.5700 100 1+

Reagent Pair 5 ( low) 2.0000 1.9613  98 2.248  112 14+

Reagent Pair 5 ( high) 2.4000 2.4299  101 2.409  100 1

Freshwater Pair 1 1.5000 1.4110 1.4320 95 1.4870 1.3870 96 1+

* Freshwater Pair 2 0.9743 0.8387 0.8804  0.8819 0.8671

Freshwater Pair 3 ( low) 1.1043 0.9463  86 0.9517  86 1+

Freshwater Pair 3 ( high) 1.3043 1.1676  90 1.0830  83 8

Freshwater Pair 4 ( low) 1.7943 1.6480  92 1.593  89 3

Freshwater Pair 4 ( high) 2.1943 2.0561  94 2.034  93 1

Unfiltered Effluent 48.0100 52.4800 52.93 110 53.2500 51.72 109 0

Filtered Effluent 43.8250 46.7800 46.8900 107 47.62 46.98 108 1+