Draft Document for Peer Review  Do Not Circulate  August 2002 C 1 Appendix C Computation of Detection and Quantitation Limits INTRODUCTION This appendix supports the Technical Support Document ( TSD) for EPA's peer review of detection and quantitation concepts. It presumes that the reader has read chapters three through five of the TSD. This appendix compares detection and quantitation limits computed from data gathered by EPA. The comparison shows that, in general, detection limits derived from a single concentration such as EPA's MDL are, on average, approximately the same as detection limits derived from similar concepts such as the ACS LOD and LOQ and ISO/ IUPAC CRV and MDV, and are approximately three times lower than a single laboratory variant of ASTM's IDE; and that all quantitation limit concepts, such as EPA's ML, the ACS and ISO/ IUPAC LOQ, and a single laboratory variant of ASTM's IQE, produce approximately the same quantitation limits.

BACKGROUND The regulated industry has been commenting on EPA's method detection limit ( MDL; see the definition at 40 CFR 136, appendix B) since 1985 and on EPA's minimum level of quantitation ( ML; see, e. g., the definition in the glossary at the end of EPA Method 1631C promulgated at 40 CFR 136, appendix A) since about 1987. In the early 1990s members of the regulated industry community began providing suggestions for alternate detection and quantitation limit concepts, most notably the compliance monitoring detection level ( CMDL), compliance monitoring quantitation level ( CMQL) and the alternate minimum level ( AML). Most recently the industry community has advanced concepts for an interlaboratory detection estimate ( IDE) and interlaboratory quantitation estimate ( IQE) through ASTMInternational ( ASTM).

In response to industry's comments, EPA began a data gathering activity designed to allow evaluation of the various detection/ quantitation limit concepts. The data would be used to characterize measurement variability versus concentration for the analytes most commonly measured in, and the analytical technologies most commonly employed for, environmental measurements.

SETTLEMENT AGREEMENT In October of 2000, EPA signed an agreement associated with promulgation of EPA Method 1631 to settle a lawsuit brought by certain members of the regulated industry ( the " Settlement Agreement"). The Settlement Agreement required EPA to, among other things, reassess detection and quantitation limit concepts, perform a peer review of the reassessment, and if warranted, propose changes to the MDL and ML or propose alternate concepts. This document supports EPA's reassessment.

EPA'S APPROACH TO ESTABLISHING DETECTION AND QUANTITATION LIMITS IN ANALYTICAL METHODS The Engineering and Analysis Division ( EAD) within EPA's Office of Science and Technology develops analytical methods for use in EPA's Clean Water Act ( CWA) programs. In developing these methods, EAD first conducts a single laboratory study in which an MDL and ML are determined followed by multiple single laboratory studies in which the MDL and ML are either verified or if necessary, revised. Then, if resources, time, and applications of the method warrant, an interlaboratory Draft Document for Peer Review  Do Not Circulate  August 2002 C 2 study is conducted in which the MDL and ML are further verified or, if necessary, revised. To establish that an MDL is realistic, EAD generally selects the highest MDL from among the MDLs determined by laboratories in the various studies or that can be verified by laboratories in the studies. For example, EPA determined the MDL in Method 1631 ( mercury by cold vapor atomic fluorescence) as 0.05 ng/ L in a single laboratory and revised this MDL to 0.2 ng/ L based on multiple single laboratory studies. All laboratories verified the MDL of 0.2 ng/ L in an interlaboratory study. Thus, although critics of the MDL have complained that the MDL is a single laboratory concept that is highly variable and produces unrealistically low MDLs, the process used by EAD to establish the MDL and resulting ML is conservative and protects against unrealistically low MDLs and MLs.

EPA'S VARIABILITY VERSUS CONCENTRATION STUDIES (" EPISODE 6000")

In 1997 and 1998, EPA conducted a study of variability vs. concentration for a number of analytical methods. Six laboratories were employed for the analyses; each analyte and method combination was tested by one of these laboratories. Details of the study design are described in EPA's Study Plan for Characterizing Variability as a Function of Concentration for a Variety of Analytical Techniques ( July 1998). Based on the sampling episode number assigned to the study by the EPA Sample Control Center, the study and results have become known as the Episode 6000 study and data.

The analytes and analytical techniques studied were:

C Total suspended solids ( TSS) by gravimetry C Metals by graphite furnace atomic absorption spectroscopy ( GFAA) C Metals by inductively coupled plasma atomic emission spectrometry ( ICP/ AES) C Hardness by ethylene diamine tetraacetic acid ( EDTA) titration C Phosphorus by colorimetry C Ammonia by ion selective electrode C Volatile organic compounds by purge and trap capillary column gas chromatography with a photoionization detector ( GC/ PID) and electrolytic conductivity detector ( GC/ ELCD) in series C Volatile organic compounds by gas chromatography with a mass spectrometer ( GC/ MS) C Available cyanide by flow injection/ ligand exchange/ amperometric detection C Metals by inductively coupled plasma spectrometry with a mass spectrometer ( ICP/ MS)

In the study, an initial ( range finding) MDL was determined for each combination of analyte and analytical technique using a revised draft of the MDL procedure. The revised draft had three significant changes: ( 1) the definition was more closely conformed to the MDL procedure; ( 2) optional iterative step 7 of the MDL procedure was made mandatory; and ( 3) the spike concentration to MDL ratio was reduced from 5 to 3 in an attempt to narrow the resulting MDL. During data gathering two laboratories complained that the reduction in spike to determined MDL ratio from 5 to 3 caused a large number of iterations and stated that 5 was more reasonable. Subsequently, EPA returned to the spike to MDL ratio of 5 published in the 40 CFR 136, Appendix B procedure.

After determining the initial MDL, each laboratory analyzed 7 replicates of samples spiked at concentrations of 100, 50, 20, 10, 7.5, 5.0, 3.5, 2.0, 1.5, 1.0, 0.75, 0.50, 0.35, 0.20, 0.15, and 0.10 times the initial MDL. In a few instances laboratories analyzed more than 7 replicates. Results associated with the replicate analyses at each concentration level were obtained, as often as possible, using the same calibration that was used in determining the initial MDL. Where laboratory reports indicated that multiple calibrations were conducted, the association between each result and its calibration was used in the data analysis. Draft Document for Peer Review  Do Not Circulate  August 2002 C 3 Spiked aqueous solutions were analyzed in order from the highest concentration ( 100 times the MDL) to the concentration at which 3 or more non detects ( zeros) were encountered among the 7 replicates, or the lowest concentration specified ( 0.1 times the MDL), whichever occurred first. This analysis order ( 1) minimized carryover that could occur in some methods if a low concentration sample had followed a high concentration sample ( as may happen when samples are analyzed in random order), and ( 2) prevented collection of a large number of zeros if the signal disappeared.

A variant of the iterative MDL procedure was used for organic compounds determined by chromatographic methods. Methods for organics normally list many ( 15 to 100) analytes, and the response for each analyte is different. Therefore, to determine an MDL for each analyte, the concentration of the spike would need to be inversely proportional to the response. Making a spiking solution with 15 to 100 different concentrations is cumbersome and error prone. The approach used in the study was to run 7 replicates at decreasing concentrations until signal extinction, then select the concentration( s) appropriate for the MDL for each analyte according to the MDL procedure. In some cases the laboratories selected the concentrations, in others cases, EPA did. This approach was generally applied for organics analysis. However, laboratories also had the option of using some combination of monotonically decreasing concentrations described above and a few selected concentrations to achieve the desired spiking levels.

DATA ANALYSIS Data from the study were used to evaluate detection and quantitation limit concepts that employ a point estimate or employ a model of variability versus concentration. Concepts that were evaluated and that employ a point estimate were the:

C EPA method detection limit ( MDL) and minimum level of quantitation ( ML); C American Chemical Society ( ACS) limit of detection ( LOD) and limit of quantitation ( LOQ); C International Standards Organization/ International Union of Pure and Applied Chemistry ( ISO/ IUPAC) critical value ( CRV), detection limit ( also termed " minimum detectable value" ( MDV)), and LOQ.

Concepts that were evaluated and employ a model of variability versus concentration were the ASTM interlaboratory detection estimate ( IDE) and interlaboratory quantitation estimate ( IQE).

COMMONALITY OF CONCEPTS The EPA, ACS, and ISO/ IUPAC concepts are all multiples of the standard deviation of either replicate measurements of a blank or of the lowest spike concentration that produces positive ( non zero) results for all 7 replicates. Although some would argue that this difference is significant, in practice they are functionally analogous because a non zero result is needed to compute any concept ( a zero result will return zero as the detection or quantitation limit).

Other subtle distinctions are that ( 1) ISO/ IUPAC suggest a false positive rate of 5 % (" = 0.05) for the CRV and MDV, whereas EPA specifies a false positive rate of 1 % (" = 0.01) for the MDL and ( 2) the EPA MDL was calculated by pooling data from two concentration levels after determining that the variabilities of the two concentration levels are not significantly different ( as stipulated in step 7 of the revised MDL procedure), thereby increasing the degrees of freedom to 12 from the 6 used in computation of the ISO/ IUPAC CRV and ACS LOD. The consequence of distinction ( 1) is that a concept with a higher allowed false positive rate (" = 0.05) will produce a lower detection limit than a concept with a lower false positive rate (" = 0.01). The consequence of distinction ( 2) is that a detection limit resulting Draft Document for Peer Review  Do Not Circulate  August 2002 C 4 from pooling at two levels will be lower and more stable than a detection limit at a single level ( given the same variability at each level) because the degrees of freedom are increased in the t statistic.

The ACS and ISO/ IUPAC concepts specify replicate measurements of a blank. In computing detection and quantitation limits from the Episode 6000 data, if the blank returned non zero results, the concepts were computed using replicate measurements of the blank. If the blank returned a zero result in any of the 7 measurements, the lowest spike concentration ( or, in the case of the MDL, two lowest spike concentrations) that produced a non zero result was used for computation of all concepts. This simplification condensed the EPA MDL and the ACS LOD to a single concept subsequently termed the EPA/ ACS DL. Similarly, the EPA ML and ACS LOQ were condensed to a single concept, termed the EPA/ ACS QL.

The remaining single point concepts were the ISO/ IUPAC CRV, MDV, and LOQ. The ISO/ IUPAC CRV differs from the EPA/ ACS DL because of its suggested use of a false positive rate of 5% (" = 0.05) versus use of a false positive rate of 1 % (" = .01) in the EPA/ ACS DL. The ISO/ IUPAC MDV also differs from the EPA/ ACS DL because of ( 1) its suggested use of a false positive rate of 5 % (" = 0.05), ( 2) its false negative rate of 5 % ($= 0.05), and ( 3) recovery correction ( estimated using a linear regression). Therefore, the ISO/ IUPAC CRV and MDV were each treated separately ( were not combined with another concept) from the other detection limit concepts in the data analysis. The ISO/ IUPAC LOQ is also different from the other quantitation limit concepts and was treated separately from these concepts.

The ASTM IDE and IQE were treated separately because they are constructed by fitting a model to variability versus concentration data, rather than being derived from the standard deviation of replicate measurements of a single concentration, as are the EPA, ACS, and ISO/ IUPAC concepts. Similar to some of the ISO/ IUPAC concepts, the ASTM IDE and IQE include protection against false negatives and recovery correction. The IQE, but not IDE, also includes an added correction for the bias associated with an estimate of the true standard deviation at each concentration. In the context of the IQE, the word " bias" means the amount by which the estimated sample standard deviation is low compared to the true population standard deviation, and should not be confused with common use of the word " bias" in an analytical measurement.

SINGLE LABORATORY VARIANTS OF INTERLABORATORY CONCEPTS EPA's Episode 6000 database contains single laboratory data because of the prohibitive expense that would have been incurred in gathering interlaboratory data. Because the EPA, ACS, and ISO/ IUPAC concepts are single laboratory concepts, and the ASTM IDE and IQE are interlaboratory concepts, the ASTM concepts could not be computed using the single laboratory data in the Episode 6000 studies. To solve this problem, single laboratory variants of the IDE and IQE were used. These single laboratory variants were termed the SL IDE and SL IQE for " single laboratory IDE" and " single laboratory IQE." The SL IDEs and SL IQEs were constructed using the overall standard deviation within a single laboratory at each concentration rather than the overall standard deviation across all laboratories at each concentration.

ATTEMPTED APPLICATION TO INTERLABORATORY DATA EPA attempted to apply the various concepts to interlaboratory study data in response to a request by the Petitioners to the Settlement Agreement and so that detection and quantitation limits could be compared. However, because the EPA, ACS, and ISO/ IUPAC concepts are single laboratory concepts whereas the ASTM concepts are interlaboratory concepts, it was not possible to compute directly comparable detection and quantitation limits from the same data. Draft Document for Peer Review  Do Not Circulate  August 2002 C 5 What was possible was to compare detection and quantitation limits produced by EPA and the Electric Power Research Institute ( EPRI) for the EPA Method 1631 and EPA Method 1638 interlaboratory study data. Although the resulting detection and quantitation limits are single or interlaboratory, as appropriate to the particular concept; i. e., apples versus oranges, their magnitudes are informative. The EPRI detection and quantitation limits are from EPRI reports of the results of the Method 1631 and Method 1638 studies.

COMPUTATIONS All computations were carried out using Statistical Analysis System ( SAS) version 8.01. The equations for all concepts were programmed into the SAS software by a senior statistician, with assistance from senior analysts. There is some ambiguity in the IUPAC/ ISO and ASTM detection and quantitation limit concepts and in interpretation of results from the ASTM concepts. Several formulas are given in the IUPAC/ ISO documentation, but none are defined to be the official ISO/ IUPAC detection and quantitation limit concepts. Therefore, calculations for the CRV, MDV, and LOQ were chosen because they were most representative of Lloyd Currie's definitions of a critical value, detection limit and quantitation limit. The specific equations used are on the CD ROM that supports this Appendix. Ambiguity in results from the ASTM concepts is attributable to the subjective nature of interpreting residual plots for each analyte. To resolve this issue, IDE and IQE models were chosen using significance tests for slope and curvature.

References used for the IUPAC/ ISO concepts were those published by Currie in Pure and Applied Chemistry 67: 10, 1699 1723 ( 1995) as updated by Analytica Chimica Acta 391 105 126 ( 1999). Where needed, the ASTM concepts were programmed as single laboratory variants of the Practices D 6091 ( IDE) and D 6512 ( IQE). EPA has included the SAS program code on the CD ROM that supports this document.

DATASETS EVALUATED EPA computed EPA/ ACS DLs and QLs; ISO/ IUPAC CRVs, MDVs and LOQs; and singlelaboratory variants of ASTM IDEs ( SL IDEs) and IQEs ( SL IQEs) for the Episode 6000 data. EPA also computed IDEs and IQEs for the Method 1631 and 1638 interlaboratory study data.

DATASETS NOT EVALUATED The Petitioners and Intervenor to the Settlement Agreement provided the list of datasets shown in Table 1 and suggested that EPA evaluate detection/ quantitation limit concepts using the datasets on the list. However, in reviewing the datasets suggested, EPA determined that many were developed for characterizing the behavior of an analyte or analytes across the analytical range of a method, rather than in the region of detection and quantitation, while others did not result from the IDE and IQE procedures. For example, any dataset developed prior to the advent of the IDE and IQE would be inappropriate because there could not have been an estimate of IDE0 or IQE0. This eliminates all datasets in Table 1 except the EPA/ EPRI Method 1631 and Method 1638 dataset, and the MMA 2001 2 dataset. It is possible that some value in one or more of the datasets developed prior to the advent of the IDE and IQE would fortuitously meet the IDE/ IQE criteria. But the IDE and IQE can be circular; i. e., once developed from a given dataset there may be a value in the dataset than can be construed to meet the criteria. The point is that datasets developed without following the IDE and IQE procedures, particularly without making an a priori estimate of IDE0 or IQE0, do not meet the requirements of the IDE and IQE procedures, regardless of whether the data in them can be construed to have met those requirements after the fact. 1 Treating each laboratory separately would lead to further ambiguities because results from some laboratories could produce detection and quantitation limits greater than the single concentration limits whereas results from other laboratories could produce detection and quantitation limits less than the single concentration limits. Given the variability of the data, such an outcome would be virtually assured and would provide no further useful information.

Draft Document for Peer Review  Do Not Circulate  August 2002 C 6 In addition, these datasets do not lend themselves to the comparisons used in this report because ( 1) they contain interlaboratory data that cannot be reduced to single laboratory data without treating each laboratory separately1 and ( 2) the developers of these datasets did not apply EPA's procedure and measurements for establishing an MDL and ML, so an MDL and ML could not be determined for making comparisons ( see the section titled " EPA's Approach to Establishing Detection and Quantitation Limits in Analytical Methods").

Further, the EPA 6000 dataset is comprehensive in coverage of analytes, analytical techniques, and a concentration range from 0.1 to 100 times the MDL, whereas the datasets suggested by Petitioners focus on metals, one organic analyte ( PCBs), and concentrations across the analytical range of the method. The range of data used for construction of an IDE or IQE is particularly important. As detailed in the discussion of the " Effect of number and spacing of concentrations for determination of the SL IDE and SL IQE" below, including data across the analytical range in calculation of an SL IDE significantly raises the SL IDE.

As stated in the section titled " Attempted Application to Interlaboratory Data" EPA used the EPA Method 1631 and 1638 datasets in computations of detection and quantitation limits, with the qualifiers given in that section. The EPA Method 1631 and Method 1638 datasets were the only datasets suggested by the Petitioners that were used.

RESULTS OF COMPUTATIONS Detection and quantitation limits are presented in a set of tables for the Episode 6000 study and a single table for the Method 1631 and Method 1638 studies. Within the Episode 6000 dataset, results for detection limits are compared followed by results for quantitation limits. Within the comparison of limits ( detection or quantitation), the first table compares the actual limits followed by a table of ratios between limits. These tables are followed by a rank comparison table, making a total of five tables for this dataset.

EPISODE 6000 DATA Table 2 compares detection limits produced by the four concepts ( EPA/ ACS DL; ISO/ IUPAC CRV; ISO/ IUPAC MDV; and ASTM SL IDE) and Table 3 compares the ratio between these concepts, taking the EPA/ ACS DL as reference. The ISO/ IUPAC CRV was greater than the corresponding EPA/ ACS DL for 26% of the analytes and methods. The median ratio of ISO/ IUPAC CRV to EPA/ ACS DL was significantly less than 1 based on the sign test with " = 0.05 ( p< 0.0001). We believe that the major reason for the difference is the different Type I error rate for the two concepts (" = 0.01 for the EPA/ ACS DL and " = 0.05 for the ISO/ IUPAC CRV).

The median ratio between the ISO/ IUPAC MDV and the EPA/ ACS DL is 1.2; i. e., the ISO/ IUPAC MDV is a median of 1.4 times higher than the EPA and ACS concepts. The ISO/ IUPAC MDV was greater than the corresponding EPA/ ACS DL for 57% of the analytes and methods. The median ratio of ISO/ IUPAC MDV to EPA/ ACS DL did not differ significantly from 1 based on the sign test with " = 0.05 ( p= 0.055). The likely reason that the two concepts do not yield significantly different results is that the correction for false negatives and recovery correction in the MDV ($ = 0.05) are counteracted by the smaller Type I error rate for the EPA/ ACS DL. Draft Document for Peer Review  Do Not Circulate  August 2002 C 7 The median ratio between the ASTM SL IDE and the EPA/ ACS DL is 2.9; i. e., the singlelaboratory variant of the ASTM IDE is a median of 2.9 times higher than the EPA and ACS concepts. The SL IDE was greater than the corresponding EPA/ ACS DL for 91% of the analytes and methods. The median ratio differed significantly from 1 based on the sign test with " = 0.05 ( p< 0.0001). The reason( s) for the difference could not be determined easily because of the number of confounding factors included in the ASTM SL IDE.

Table 4 compares quantitation limits produced by the three concepts ( EPA/ ACS QL; ISO LOQ; and ASTM SL IQE) and Table 5 compares the ratio between these concepts taking the EPA/ ACS QL as reference. The median ratio between the ISO/ IUPAC LOQ and the EPA/ ACS QL is 0.92, and the median ratio between the ASTM SL IQE and the EPA/ ACS QL is 1. The ISO LOQ and ASTM SL IQE are greater than the corresponding EPA/ ACS QL for 43% and 51% of the analytes and methods, respectively. The median ratio did not differ significantly from 1 based on the sign test at " = 0.05 ( LOQ: p= 0.062; SL IQE: p= 0.78) The reason( s) why the ASTM SL IQE, ISO LOQ, and the EPA/ ACS QL produce nearly identical limits could not be determined easily because of the number of confounding factors included in the ASTM SL IQE.

Some of the differences or similarities in median quantitation limits may be accounted for by rounding in the ML procedure, although the rounding should average over the large number of analytes examined.

Table 6 gives the frequency comparisons for the detection and quantitation limits; i. e., the frequency with which each concept produced the highest or lowest quantitation limit.

EPA/ EPRI METHOD 1631 AND 1638 INTERLABORATORY METHOD VALIDATION STUDY DATA Table 7 compares detection and quantitation limits computed from data generated in the Method 1631 and Method 1638 interlaboratory studies. MDLs and MLs are those listed in EPA Methods 1631 and 1638. EPA computed IDEs and IQEs for the purpose of preparing this report. IDEs and IQEs computed by EPRI are from the EPRI reports on EPA Method 1631 and Method 1638 studies.

In reviewing these data it must be recognized that the EPA MDLs and MLs are the result of selecting the highest MDL in EPA's single laboratory studies or among MDLs from the interlaboratory study, whereas the IDEs and IQEs are the result of a statistical process that includes recovery correction, correction for bias in the sample standard deviation ( IQE only), allowance for prediction and tolerance intervals, interlaboratory variability, and model selection. The most significant reason for the instances of a large disparity between the EPA determined IDEs/ IQEs and the EPRI determined IDEs/ IQEs is model selection. EPA selected the model based on a strict application of the IDE and IQE procedures by a senior statistician. For those instances in which EPA and EPRI selected the same model, the IDEs and IQEs are nearly the same.

Table 8 compares IDEs resulting from the four main model types described in the ASTM IDE and IQE procedures. IDEs resulting from the constant model were the highest for all analytes. IDEs resulting from the other three models were almost equal for some analytes ( lead, for example), and differed by more than an order of magnitude for others ( mercury, for example). For two analytes, the IDE estimated using the linear model was negative. This was due to a negative intercept estimate in the precision model. The ASTM IDE and IQE procedures dictate that the linear model should not be used in this situation. No IDE could be calculated using the hybrid model for silver, because the IDE did not converge to a single value using the calculated model for precision. This failure to converge is consistent with results for this analyte presented by EPRI. Draft Document for Peer Review  Do Not Circulate  August 2002 C 8 DISCUSSION Negative detection limits for the ISO/ IUPAC MDV The calculated MDV was negative for 26 analytes in the Episode 6000 data. Negative MDVs are attributable to the use of a regression model to estimate recovery at each concentration. The standard errors and correlation of the regression parameters are included in the calculation of the MDV. Analytes for which the MDV was negative seemed to coincide with an unusually large standard error of the regression intercept, which generally occurred when the estimated intercept was strongly negative. The large standard error of the intercept was likely due to extrapolating the recovery model to zero concentration; the error around a regression line is greatest for concentrations furthest away from the mean spike level. The effect of this extrapolation may also be seen in the Episode 6000 data. No negative results were used in the MDV and LOQ calculations, yet the median recovery intercept for these analytes was equal to  0.10. The standard errors of the intercept and slope estimates were generally high ( intercept median= 0.25, slope median= 0.010), and therefore the estimated intercept and slope terms were frequently not significantly different from 0 and 1, respectively ( intercept: not different from zero for 166 analytes/ methods; slope not significantly different from 1 for 106 analytes; both intercept and slope not significant for 78 analytes). Because the recovery model parameters are not significant for the majority of analytes, and both the estimated slope and the standard errors of the slope and intercept are included in the calculation of the MDV and LOQ, the inclusion of the recovery model estimates may bias the calculated limits, to the point that the resulting MDV can be negative.

Effect of number and spacing of concentrations for determination of the SL IDE and SLIQE Tests in the Episode 6000 studies were conducted at 16 concentration levels. The IDE procedure suggests 5 concentration levels. Based on statistical theory we would the expect the number and spacing of concentration levels to affect the outcome, with a larger number of concentrations producing a more reliable estimate. We used the Episode 6000 dataset to test this hypothesis.

The IDE procedure suggests spike concentrations at 0.5, 1.0, 2, 4, and 8 times an initial estimate of the IDE ( IDE0). IDE0 is estimated at 10 times the standard deviation of replicates of a blank or the lowest level that can be measured. EPA's Episode 6000 database contain results of analysis of 7 replicates at 16 concentration levels from 0.1 to 100 times the initial estimate of the MDL ( a factor of 1000). Between 0.1 and 10 times the MDL, the data are spaced a factor of approximately 1.5 apart. Above 10 times the MDL, the data are spaced at 10, 20, 50 and 100 times the MDL. The reason for the narrow spacing between 0.1 to 10 times the MDL was to attempt to allow more precise characterization of variability in the region of the MDL.

The SL IDEs and SL IQEs in Tables 2 and 4, respectively, were computed and reported using all 16 concentration levels because data were available at all of these levels. However, to determine the effect of the IDE procedure, a separate data analysis was performed. In this separate analysis, concentration levels were limited to a total of 5, and the 5 levels were selected to be as consistent as possible with the levels specified in the IDE procedure; i. e., at 5, 10, 20, 40, and 80 times the standard deviation of replicate measurements of a blank or the lowest level at which measurements could be made. The statement " lowest level at which measurements can be made" can be interpreted to mean inclusion or exclusion of results containing zeros and/ or negative numbers. For purposes of the evaluation, concentrations that produced results containing a zero or negative number were excluded; i. e., the lowest concentration that contained no zeros or negative numbers was chosen as the concentration at which the standard deviation would be calculated for the purpose of estimating IDE0 and IQE0. Although some Draft Document for Peer Review  Do Not Circulate  August 2002 C 9 statisticians may argue that zeros and negative numbers should be included, nearly all analytical chemists would eliminate such numbers because they have no physical meaning.

The SL IDE was calculated after selecting the levels based on IDE0 and the results were compared to results produced when all 16 levels were included in calculating the SL IDE. Results are summarized in Table 9. This table shows that the median 16 point IDE is approximately 1.3 times greater than the median 5 point IDE. For those instances in which the same model was chosen ( 108 out of 198), the median 16 point IDE was approximately 1.4 times higher than the median 5 point IDE, which was significantly different from 1.0 based on a sign test ( p < 0.0001). For those instances in which a different model was chosen ( 90 out of 198), the median 16 point IDE was approximately 0.9 times the median 5 point IDE, which was not significantly different from 1.0 ( p = 0.83). Because the choice of model can have a confounding effect on any differences between 16 point and 5 point SL IDEs, the focus should be on the instances in which the same model was chosen. For these instances, the results indicate that only data in the region of detection and quantitation should be used to establish a detection or quantitation limit.

Parallel reasoning can be applied to the IQE, because IQE0 is specified and the IQE is developed in a way analogous to that for the IDE.

RSD AT THE ML IN THE EPISODE 6000 STUDY The minimum level of quantitation ( ML) is directed at the level at which 10% relative standard deviation ( RSD) is attained. However, because the ML is not established at exactly 10% RSD, but is determined by multiplying the standard deviation that is obtained in determination of an MDL by 10 ( as recommended by both ACS and Currie for ACS and ISO/ IUPAC LOQs), the resulting RSD may not be 10%. The Episode 6000 data provided the opportunity to determine the actual value of the RSD at the ML. Results of the determination showed that the overall median RSD at the ML across all 198 analytes in the Episode 6000 study was 7 %, and the median RSD per analytical technique ranged between 6 and 16 percent by analytical technique for analytes in the 10 analytical techniques in the study. For 126 of the 198 individual analytes, the RSD fell between 5% and 15%. For the majority of the analytes that fell outside this range ( 56 out of 72), the RSD was less than 5%.

There was a spike concentration at the ML for approximately 80 percent of the analytes in the Episode 6000 study so the RSD could be determined directly for these analytes. For a few analytes there was not a spike concentration at the ML, and the RSD was determined by interpolation between spike levels for these analytes. However, for 82 out of 198 analytes, the concentration at the ML was below the range of the data; i. e., below the lowest spike concentration that returned non zero and non negative results. These instances were for organic analytes determined by EPA Methods 502.2 and 524.2. The reason that these low values occur is because hardware and/ or software thresholds in chromatographic instruments that are set to eliminate spurious noise signals also filter out responses at low concentrations. For instances in which this occurred, the ML was calculated as the lowest concentration at which nonzero and non negative results were not reported, and the RSD was calculated at this concentration. The median RSD for these analytes was 5%, compared to a median of 9% where this did not happen.

CONCLUSIONS The comparisons of detection and quantitation limits show high variability among the limits calculated using the different concepts, even with data containing 7 replicates at 16 concentration levels ( see the summary statistics at the end of Tables 3 and 5, Table 6, and the final conclusion below). The net effect is that the systematic differences among detection and quantitation limits produced by the various concepts are overwhelmed by variability; i. e., there is a small systematic difference among the concepts Draft Document for Peer Review  Do Not Circulate  August 2002 C 10 but great variability in the detection and quantitation limits for a given analyte. This result is not surprising given the variability of data in the region of detection and quantitation. However, it is difficult to postulate a solution to the problem. Gathering more data in the region of detection and quantitation would appear to be a solution, but 91 data points were gathered for each analyte in the region between 0.1 and 10 times the MDL in the Episode 6000 studies, and it is unlikely that any organization could afford to gather even this amount of data for determination of a detection limit. Given the high degree of variability of the data, EPA's approach of conducting single laboratory study to gain a first estimate, then multiple single laboratory studies to verify or revise the estimate, then an interlaboratory study, where warranted, to further verify and revise the estimate, is a reasonable means of establishing detection and quantitation limits because of the checks and balances that occur at each step.

A second conclusion is that using a regression line to estimate a recovery correction at zero concentration causes great swings in the resulting detection and quantitation limits such as the ISO/ IUPAC MDV and LOQ. The estimated regression parameters for the recovery models were often not significant, and the inclusion of the estimated slope and the standard errors of the slope and intercept will therefore unnecessarily bias the calculated MDV and LOQ, such that the calculated MDVs may be negative ( see Discussion section " Negative detection limits for the ISO/ IUPAC MDV, and Table 2 for instances of negative detection limits"). The estimated recovery model used in calculating the IDE and IQE is also strongly affected by the chosen model of variability vs. concentration ( see Table 8). Even though a linear regression is used to model recovery in each case, the weights used in the model are calculated based on the variability model, and can vary greatly when the number of concentrations used is low. For the Episode 6000 data, the median RSD of the recovery slopes from the four different models used in the IDE calculations for a given analyte and method was 5%. In addition, for 75 of the analytes and methods ( 38%), at least one estimated recovery slope was greater than 1, and at least one was less than 1. This suggests that the method could be considered to be high biased ( and the final IDE and IQE would be decreased by the recovery correction) and low biased ( and the final IDE and IQE increased) for the analyte, depending on the chosen precision model. For many analytes the slopes were not significantly different from 1, suggesting that a recovery correction may not be appropriate at all. This is in addition to the philosophical issue as to whether recovery correction is warranted. If there is to be a correction for recovery, it may be better to use some average or median value than a regression, or use a measured value near the region of interest.

A third conclusion is that further work will need to be done on the ASTM IDE and IQE before they can be used routinely, not only because of the complexity of the procedures, but also because of the ambiguity in determining that the correct model has been selected. ( For the consequences of model selection, compare the IDEs and IQEs determined by EPA and EPRI in Table 7, and the IDEs calculated from the different model types in Table 8. Some differ considerably as a result of model selection in application of the IDE and IQE procedures by different statisticians.)

A fourth conclusion is that quantitation limit concepts such as EPA's ML and the ACS and ISO/ IUPAC LOQ that are directed 10% RSD actually produce RSDs that are in the range of the 10% intended ( see the discussion in the Section titled " RSD at the ML in the Episode 6000 Study"). The median RSDs for each method in the Episode 6000 dataset ranged from 6% to 16%, and 64% of the individual analyte RSDs fell between 5% and 15%.

Finally, a statement needs to be made about the overall philosophy behind the concepts. A natural progression through time is to refine any theory or concept. However, in the case of detection and quantitation in analytical chemistry ( and as applied to other disciplines), the effort to further refine concepts may be futile, given the variability of the data that must be used with any concept. However, it is clear no concept produces the " right" answer. Different concepts allow for different sources of variability resulting in shifts in the magnitude of the limit. For the EPA, ACS, ISO/ IUPAC, and ASTM Draft Document for Peer Review  Do Not Circulate  August 2002 C 11 concepts, the most significant causes of this shift appear to be ( 1) the false positive rate (" = 0.01 or 0.05), ( 2) the allowance for false negatives ($ = 0.05), ( 3) recovery correction, ( 4) correction for the bias in the calculated standard deviation ( IQE only), ( 5) interlaboratory variability, and ( 6) model selection in the IDE and IQE.

TABLES Table 1. Datasets Suggested by Petitioners Dataset and year Analyte and technology AAMA 1996 7 Metals by ICP/ AES ( 200.7)

AAMA 1996 7 Mercury by CVAA ( 245.2)

AAMA 1996 7 PCBs by GC/ ECD ( 608.2)

MMA 2000 1 PCB 1216 and 1260 by GC/ ECD EPA/ EPRI 1997 8 Mercury by CVAF ( 1631)

EPA/ EPRI 1997 8 Metals by ICP/ MS ( 1638)

EPRI 1987 Metals by GFAA ( EPA 200)

EPRI 1990 Metals by ICP/ AES ( EPA 200.7)

EPRI 1994 Al, Be, Tl by GFAA ( EPA 200)

EPRI 1996 Cd, As, Cr by GFAA ( EPA 200) Draft Document for Peer Review  Do Not Circulate  August 2002 C 12 Table 2. Comparison of Detection Limits ( µ g/ L except where footnoted) for the Episode 6000 Dataset Analyte Method Procedure EPA/ ACS DL ISO CRV ISO MDV ASTM SL IDE 1,1,1,2 tetrachloroethane 502.2 ELCD 0.041 0.028 0.054 0.028 1,1,1,2 tetrachloroethane 524.2 0.052 0.039  0.030 0.206 1,1,1 trichloroethane 502.2 ELCD 0.012 0.009 0.017 0.035 1,1,1 trichloroethane 524.2 0.055 0.021 0.007 0.268 1,1,2,2 tce+ 1,2,3 tcp 502.2 ELCD 0.064 0.225 0.417 0.170 1,1,2,2 tetrachloroethane 524.2 0.132 0.131 0.139 0.377 1,1,2 trichloroethane 502.2 ELCD 0.024 0.055 0.103 0.026 1,1,2 trichloroethane 524.2 0.075 0.043 0.045 0.284 1,1 dichloroethane 502.2 ELCD 0.010 0.008 0.016 0.066 1,1 dichloroethane 524.2 0.033 0.020 0.018 0.206 1,1 dichloroethene 502.2 ELCD 0.038 0.013 0.032 0.193 1,1 dichloroethene 524.2 0.054 0.035  0.030 0.278 1,1 dichloropropanone 524.2 5.184 3.146 5.657 6.032 1,1 dichloropropene 524.2 0.045 0.012  0.020 0.247 1,2,3 trichlorobenzene 502.2 ELCD 0.048 0.308 0.599 0.122 1,2,3 trichlorobenzene 502.2 PID 0.057 0.301 0.623 0.114 1,2,3 trichlorobenzene 524.2 0.070 0.040 0.036 0.259 1,2,3 trichloropropane 524.2 7.328 0.046 0.042 1.206 1,2,4 trichlorobenzene 502.2 ELCD 0.022 0.189 0.393 0.077 1,2,4 trichlorobenzene 502.2 PID 0.070 0.221 0.471 0.124 1,2,4 trichlorobenzene 524.2 0.053 0.050 0.057 0.208 1,2,4 trimethylbenzene 502.2 PID 0.095 0.075 0.167 0.123 1,2,4 trimethylbenzene 524.2 0.012 0.009 0.017 0.129 1,2 dibromo 3 chloropropane 524.2 1.457 0.391 0.702 1.619 1,2 dibromoethane 502.2 ELCD 0.096 0.028 0.056 0.143 1,2 dibromoethane 524.2 0.127 0.117 0.175 0.289 1,2 dichlorobenzene 502.2 ELCD 0.035 0.073 0.144 0.053 1,2 dichlorobenzene 502.2 PID 0.033 0.024 0.054 0.147 1,2 dichlorobenzene 524.2 0.030 0.023  0.010 0.112 1,2 dichloroethane 502.2 ELCD 0.017 0.017 0.032 0.037 1,2 dichloroethane 524.2 0.039 0.024 0.017 0.229 1,2 dichloropropane 502.2 ELCD 0.023 0.196 0.393 0.037 1,2 dichloropropane 524.2 0.056 0.031 0.029 0.221 1,3,5 tmb+ 4 chlorotoluene 502.2 PID 0.067 0.201 0.449 0.108 Table 2. Comparison of Detection Limits ( µ g/ L except where footnoted) for the Episode 6000 Dataset Analyte Method Procedure EPA/ ACS DL ISO CRV ISO MDV ASTM SL IDE Draft Document for Peer Review  Do Not Circulate  August 2002 C 13 1,3,5 trimethylbenzene 524.2 0.011 0.008 0.009 0.117 1,3 dichlorobenzene 502.2 ELCD 0.035 0.048 0.104 0.100 1,3 dichlorobenzene 502.2 PID 0.093 0.134 0.297 0.123 1,3 dichlorobenzene 524.2 0.023 0.016  0.010 0.126 1,3 dichloropropane 502.2 ELCD 0.016 0.071 0.135 0.045 1,3 dichloropropane 524.2 0.038 0.024  0.010 0.170 1,4 dichlorobenzene 502.2 ELCD 0.026 0.101 0.198 0.054 1,4 dichlorobenzene 524.2 0.023 0.017  0.040 0.110 1 chlorobutane 524.2 0.020 0.016 0.019 0.200 2,2 dichloropropane 524.2 2.376 0.103  0.120 0.700 2 butanone 524.2 0.417 0.297 0.515 0.775 2 chlorotoluene 502.2 ELCD 0.108 0.162 0.318 0.184 2 chlorotoluene 502.2 PID 0.238 0.454 1.022 0.222 2 chlorotoluene 524.2 0.016 0.009 0.003 0.121 2 hexanone 524.2 1.316 0.148 0.234 0.815 2 nitropropane 524.2 0.901 0.275 0.457 0.965 4 chlorotoluene 502.2 ELCD 0.110 0.127 0.234 0.159 4 chlorotoluene 524.2 0.010 0.008 0.008 0.102 4 isopropyltoluene 524.2 0.010 0.008 0.005 0.102 4 methyl 2 pentanone 524.2 0.812 0.480 0.740 1.060 Acetone 524.2 0.859 0.440 0.806 2.025 Acrylonitrile 524.2 0.863 0.444 0.658 1.197 Allyl Chloride 524.2 0.032 0.026 0.010 0.203 Aluminum 1620 29.555 15.043 28.670 198.565 Aluminum 200.8 19.145 1.690 3.547 12.004 Ammonia as Nitrogen 1 350.3 0.010 0.007 0.014 0.013 Antimony 1620 1.552 0.801 1.754 4.087 Antimony 200.8 0.178 0.003 0.007 0.018 Arsenic 1620 1.065 0.917 1.375 1.463 Arsenic 200.8 0.226 0.137 0.272 0.346 Barium 1620 1.702 1.337 1.831 1.762 Barium 200.8 0.033 0.029 0.061 0.079 Benzene 502.2 PID 0.030 0.043 0.099 0.077 Benzene 524.2 0.014 0.014 0.027 0.115 Table 2. Comparison of Detection Limits ( µ g/ L except where footnoted) for the Episode 6000 Dataset Analyte Method Procedure EPA/ ACS DL ISO CRV ISO MDV ASTM SL IDE Draft Document for Peer Review  Do Not Circulate  August 2002 C 14 Beryllium 1620 0.528 0.339 0.408 0.428 Beryllium 200.8 0.007 0.004 0.006 0.019 Boron 1620 15.387 10.356 17.790 19.884 Bromobenzene 502.2 ELCD 0.131 0.093 0.187 0.729 Bromobenzene 502.2 PID 0.012 0.286 0.619 0.048 Bromobenzene 524.2 0.044 0.036  0.050 0.175 Bromochloromethane 502.2 ELCD 0.013 0.016 0.032 0.462 Bromochloromethane 524.2 0.125 0.113 0.165 0.309 Bromodichloromethane 502.2 ELCD 0.004 0.016 0.032 0.064 Bromodichloromethane 524.2 0.043 0.026 0.023 0.182 Bromoform 502.2 ELCD 0.006 0.009 0.016 1.450 Bromoform 524.2 0.123 0.065 0.040 0.350 Bromomethane 502.2 ELCD 0.267 0.047 0.010 6.993 Bromomethane 524.2 0.068 0.055 0.060 0.238 Cadmium 1620 0.127 0.079 0.134 0.184 Cadmium 200.8 0.004 0.007 0.012 0.011 Calcium 1620 36.726 35.822 72.400 39.651 Carbon Disulfide 524.2 0.027 0.016  0.030 0.203 Carbon Tetrachloride 524.2 0.038 0.027  0.030 0.258 Carbontet+ 1,1 dcp 502.2 ELCD 0.029 0.028 0.060 0.062 Chloroacetonitrile 524.2 0.919 0.773 1.535 1.535 Chlorobenzene 502.2 ELCD 0.011 0.016 0.034 0.440 Chlorobenzene 502.2 PID 0.030 0.080 0.178 0.062 Chlorobenzene 524.2 0.025 0.022 0.016 0.119 Chloroethane 502.2 ELCD 0.108 0.006 0.004 2.492 Chloroethane 524.2 0.066 0.041 0.042 0.336 Chloroform 502.2 ELCD 0.043 0.410 0.758 0.031 Chloroform 524.2 0.036 0.027 0.025 0.203 Chloromethane 502.2 ELCD 0.070 0.090 0.240 0.204 Chloromethane 524.2 0.045 0.036 0.066 0.215 Chromium 1620 0.310 0.254 0.386 0.478 Chromium 200.8 0.073 0.062 0.125 0.393 Cis 1,2 dce+ 2,2 dcp 502.2 ELCD 0.013 0.017 0.034 0.043 Cis 1,2 dichloroethene 524.2 0.040 0.033  0.010 0.203 Table 2. Comparison of Detection Limits ( µ g/ L except where footnoted) for the Episode 6000 Dataset Analyte Method Procedure EPA/ ACS DL ISO CRV ISO MDV ASTM SL IDE Draft Document for Peer Review  Do Not Circulate  August 2002 C 15 Cis 1,3 dichloropropene 502.2 ELCD 0.007 0.016 0.031 0.059 Cis 1,3 dichloropropene 502.2 PID 0.057 0.048 0.099 0.077 Cis 1,3 dichloropropene 524.2 0.038 0.024 0.001 0.158 Cobalt 1620 9.820 4.017 8.094 15.560 Cobalt 200.8 0.001 0.001  0.070 0.008 Copper 1620 6.046 4.990 10.510 20.328 Copper 200.8 0.037 0.027 0.053 0.770 Dibromochloromethane 502.2 ELCD 0.009 0.019 0.039 0.418 Dibromochloromethane 524.2 0.051 0.031 0.011 0.253 Dibromomethane 502.2 ELCD 0.007 0.047 0.096 0.441 Dibromomethane 524.2 0.102 0.082 0.117 0.342 Dichlorodifluoromethane 502.2 ELCD 0.009 1.453 1.715 0.087 Dichlorodifluoromethane 524.2 0.083 0.054 0.046 0.420 Diethyl Ether 524.2 0.120 0.114 0.169 0.340 Ethyl Methacrylate 524.2 0.045 0.031 0.018 0.244 Ethylbenzene 502.2 PID 0.021 0.053 0.122 0.075 Ethylbenzene 524.2 0.033 0.028  0.020 0.167 Hardness 1 130.2 0.828 0.555 1.152 2.152 Hexachlorobutadiene 502.2 ELCD 0.043 0.240 0.502 0.090 Hexachlorobutadiene 524.2 0.068 0.035  0.020 0.263 Hexachloroethane 524.2 0.056 0.049 0.044 0.234 Hexchlobutadiene+ naphthalene 502.2 PID 0.649 0.924 2.083 0.598 Iron 1620 90.409 270.433 472.200 345.686 Isopropylbenzene 502.2 PID 0.020 0.051 0.120 0.059 Isopropylbenzene 524.2 0.011 0.010 0.012 0.113 Lead 1620 1.647 1.186 1.965 2.317 Lead 200.8 0.655 0.061 0.120 0.197 M+ p Xylene 502.2 PID 0.090 0.099 0.225 0.116 M+ p Xylene 524.2 0.013 0.008 0.006 0.127 Magnesium 1620 103.033 88.729 175.300 99.662 Manganese 1620 6.856 1.081 2.591 6.531 Manganese 200.8 0.031 0.030 0.049 0.106 Mercury 200.8 0.004 0.003  0.020 0.062 Methacrylonitrile 524.2 0.356 0.228 0.368 0.643 Table 2. Comparison of Detection Limits ( µ g/ L except where footnoted) for the Episode 6000 Dataset Analyte Method Procedure EPA/ ACS DL ISO CRV ISO MDV ASTM SL IDE Draft Document for Peer Review  Do Not Circulate  August 2002 C 16 Methyl Iodide 524.2 0.025 0.023  0.010 0.173 Methyl Tert butyl Ether 524.2 0.026 0.016  0.030 0.195 Methylacrylate 524.2 0.220 0.202 0.356 0.549 Methylene Chloride 502.2 ELCD 0.128 1.835 5.018 2.727 Methylene Chloride 524.2 0.082 0.072 0.098 0.276 Methylmethacrylate 524.2 0.225 0.085 0.120 0.484 Molybdenum 1620 2.455 1.714 3.787 2.917 Molybdenum 200.8 0.004 0.003 0.000 0.262 N butylbenzene 502.2 PID 0.030 0.069 0.151 0.139 N butylbenzene 524.2 0.016 0.014 0.027 0.136 N propylbenzene 502.2 PID 0.040 0.597 1.340 0.089 N propylbenzene 524.2 0.038 0.026  0.040 0.231 Naphthalene 524.2 0.048 0.040 0.047 0.175 Nickel 1620 20.219 13.262 25.700 23.784 Nickel 200.8 0.146 0.058 0.107 0.076 o xylene 524.2 0.018 0.015  0.030 0.161 o xylene+ styrene 502.2 PID 0.059 0.118 0.263 0.111 P isoproptol+ 1,4 dcb 502.2 PID 0.073 0.152 0.332 0.153 Pentachloroethane 524.2 0.553 0.019  0.080 0.337 Sec butylbenzene 502.2 PID 0.055 0.058 0.133 0.079 Sec butylbenzene 524.2 0.014 0.011  0.010 0.132 Selenium 1620 0.849 0.619 1.493 1.915 Selenium 200.8 0.192 0.156 0.302 0.410 Silver 1620 4.907 3.588 6.495 10.219 Silver 200.8 0.004 0.002 0.004 0.010 Sodium 1620 69.530 49.595 97.650 133.007 Styrene 524.2 0.014 0.011 0.011 0.119 Tert butylbenzene 502.2 PID 0.029 0.058 0.137 0.073 Tert butylbenzene 524.2 0.022 0.012 0.023 0.170 Tetrachloroethene 502.2 ELCD 0.018 0.200 0.429 0.051 Tetrachloroethene 502.2 PID 0.062 0.319 0.753 0.157 Tetrachloroethene 524.2 0.085 0.084 0.058 0.379 Thallium 1620 0.512 0.651 1.406 1.208 Thallium 200.8 0.000 0.000 0.001 0.001 Table 2. Comparison of Detection Limits ( µ g/ L except where footnoted) for the Episode 6000 Dataset Analyte Method Procedure EPA/ ACS DL ISO CRV ISO MDV ASTM SL IDE Draft Document for Peer Review  Do Not Circulate  August 2002 C 17 Thorium 200.8 0.001 0.001 0.000 0.003 Tin 1620 3.670 2.019 3.143 1.200 Titanium 1620 4.777 4.453 8.050 5.238 Toluene 502.2 PID 0.070 0.064 0.145 0.061 Toluene 524.2 0.020 0.006 0.000 0.130 Total Phosphorus 1 365.2 0.006 0.005 0.009 0.013 Total Suspended Solids 1 160.2 1.170 0.948 1.945 2.877 Trans 1,2 dichloroethene 502.2 ELCD 0.041 0.174 0.382 0.065 Trans 1,2 dichloroethene 524.2 0.038 0.032  0.010 0.255 Trans 1,3 dichloropropene 502.2 ELCD 0.012 0.013 0.026 0.082 Trans 1,3 dichloropropene 502.2 PID 0.058 0.037 0.079 0.085 Trans 1,3 dichloropropene 524.2 0.051 0.025 0.000 0.204 Trans 1,4 dichloro 2 butene 524.2 0.512 0.348 0.589 1.182 Trichloroethene 502.2 ELCD 0.012 0.014 0.029 0.050 Trichloroethene 502.2 PID 0.027 0.043 0.098 0.096 Trichloroethene 524.2 0.061 0.058 0.062 0.288 Trichlorofluoromethane 502.2 ELCD 0.108 0.012 0.028 1.997 Trichlorofluoromethane 524.2 0.087 0.075 0.046 0.307 Uranium 200.8 0.000 0.000 0.000 0.001 Vanadium 1620 7.344 4.207 8.359 10.063 Vanadium 200.8 0.555 0.512 0.994 0.845 Vinyl Chloride 502.2 ELCD 0.270 0.039 0.072 3.521 Vinyl Chloride 524.2 0.043 0.031 0.000 0.295 WAD Cyanide 1677 0.572 0.169 0.319 0.672 Xylene ( Total) 524.2 0.009 0.005 0.008 0.111 Yttrium 1620 1.923 1.370 2.518 3.119 Zinc 1620 2.597 2.301 3.697 4.415 Zinc 200.8 0.900 0.461 0.806 1.497 1 Results reported as mg/ L Note: ELCD or PID in the Procedure column indicates the photo ionization detector ( PID) or electrolytic conductivity detector ( ELCD) in EPA Method 502.2 Draft Document for Peer Review  Do Not Circulate  August 2002 C 18 Table 3. Ratios of Detection Limits to the EPA/ ACS DL for the Episode 6000 Dataset Analyte Method Procedure ISO CRV/ MDL ISO MDV/ MDL SL IDE/ MDL 1,1,1,2 tetrachloroethane 502.2 ELCD 0.691 1.313 0.679 1,1,1,2 tetrachloroethane 524.2 0.747  0.645 3.953 1,1,1 trichloroethane 502.2 ELCD 0.707 1.387 2.861 1,1,1 trichloroethane 524.2 0.382 0.135 4.843 1,1,2,2 tce+ 1,2,3 tcp 502.2 ELCD 3.522 6.531 2.664 1,1,2,2 tetrachloroethane 524.2 0.994 1.054 2.853 1,1,2 trichloroethane 502.2 ELCD 2.266 4.207 1.062 1,1,2 trichloroethane 524.2 0.580 0.602 3.796 1,1 dichloroethane 502.2 ELCD 0.786 1.645 6.600 1,1 dichloroethane 524.2 0.596 0.561 6.281 1,1 dichloroethene 502.2 ELCD 0.348 0.845 5.018 1,1 dichloroethene 524.2 0.647  0.477 5.102 1,1 dichloropropanone 524.2 0.607 1.091 1.164 1,1 dichloropropene 524.2 0.261  0.536 5.525 1,2,3 trichlorobenzene 502.2 ELCD 6.454 12.543 2.548 1,2,3 trichlorobenzene 502.2 PID 5.268 10.902 1.988 1,2,3 trichlorobenzene 524.2 0.578 0.517 3.706 1,2,3 trichloropropane 524.2 0.006 0.006 0.165 1,2,4 trichlorobenzene 502.2 ELCD 8.731 18.213 3.548 1,2,4 trichlorobenzene 502.2 PID 3.143 6.704 1.773 1,2,4 trichlorobenzene 524.2 0.951 1.069 3.921 1,2,4 trimethylbenzene 502.2 PID 0.792 1.766 1.297 1,2,4 trimethylbenzene 524.2 0.772 1.419 10.509 1,2 dibromo 3 chloropropane 524.2 0.268 0.482 1.111 1,2 dibromoethane 502.2 ELCD 0.297 0.582 1.496 1,2 dibromoethane 524.2 0.918 1.378 2.275 1,2 dichlorobenzene 502.2 ELCD 2.079 4.106 1.525 1,2 dichlorobenzene 502.2 PID 0.734 1.649 4.514 1,2 dichlorobenzene 524.2 0.755  0.319 3.729 1,2 dichloroethane 502.2 ELCD 0.981 1.834 2.107 1,2 dichloroethane 524.2 0.609 0.445 5.882 1,2 dichloropropane 502.2 ELCD 8.543 17.176 1.602 1,2 dichloropropane 524.2 0.540 0.519 3.915 Table 3. Ratios of Detection Limits to the EPA/ ACS DL for the Episode 6000 Dataset Analyte Method Procedure ISO CRV/ MDL ISO MDV/ MDL SL IDE/ MDL Draft Document for Peer Review  Do Not Circulate  August 2002 C 19 1,3,5 tmb+ 4 chlorotoluene 502.2 PID 2.984 6.658 1.598 1,3,5 trimethylbenzene 524.2 0.710 0.843 10.494 1,3 dichlorobenzene 502.2 ELCD 1.375 2.980 2.850 1,3 dichlorobenzene 502.2 PID 1.445 3.192 1.325 1,3 dichlorobenzene 524.2 0.699  0.357 5.418 1,3 dichloropropane 502.2 ELCD 4.518 8.588 2.839 1,3 dichloropropane 524.2 0.628  0.212 4.457 1,4 dichlorobenzene 502.2 ELCD 3.876 7.630 2.068 1,4 dichlorobenzene 524.2 0.714  1.534 4.699 1 chlorobutane 524.2 0.786 0.974 10.051 2,2 dichloropropane 524.2 0.044  0.049 0.294 2 butanone 524.2 0.713 1.235 1.860 2 chlorotoluene 502.2 ELCD 1.498 2.947 1.705 2 chlorotoluene 502.2 PID 1.907 4.290 0.931 2 chlorotoluene 524.2 0.570 0.215 7.599 2 hexanone 524.2 0.112 0.178 0.620 2 nitropropane 524.2 0.305 0.507 1.071 4 chlorotoluene 502.2 ELCD 1.152 2.135 1.445 4 chlorotoluene 524.2 0.803 0.849 10.563 4 isopropyltoluene 524.2 0.833 0.519 10.452 4 methyl 2 pentanone 524.2 0.591 0.911 1.305 Acetone 524.2 0.512 0.938 2.358 Acrylonitrile 524.2 0.515 0.763 1.387 Allyl Chloride 524.2 0.820 0.306 6.297 Aluminum 1620 0.509 0.970 6.718 Aluminum 200.8 0.088 0.185 0.627 Ammonia as Nitrogen 350.3 0.668 1.358 1.229 Antimony 1620 0.516 1.130 2.634 Antimony 200.8 0.018 0.037 0.102 Arsenic 1620 0.861 1.290 1.373 Arsenic 200.8 0.606 1.206 1.532 Barium 1620 0.786 1.076 1.035 Barium 200.8 0.885 1.855 2.421 Benzene 502.2 PID 1.435 3.283 2.537 Table 3. Ratios of Detection Limits to the EPA/ ACS DL for the Episode 6000 Dataset Analyte Method Procedure ISO CRV/ MDL ISO MDV/ MDL SL IDE/ MDL Draft Document for Peer Review  Do Not Circulate  August 2002 C 20 Benzene 524.2 0.981 1.839 7.986 Beryllium 1620 0.641 0.773 0.810 Beryllium 200.8 0.564 0.846 2.667 Boron 1620 0.673 1.156 1.292 Bromobenzene 502.2 ELCD 0.711 1.428 5.575 Bromobenzene 502.2 PID 23.364 50.631 3.947 Bromobenzene 524.2 0.834  1.041 4.021 Bromochloromethane 502.2 ELCD 1.166 2.381 34.635 Bromochloromethane 524.2 0.902 1.319 2.468 Bromodichloromethane 502.2 ELCD 3.804 7.753 15.209 Bromodichloromethane 524.2 0.614 0.538 4.229 Bromoform 502.2 ELCD 1.503 2.627 242.497 Bromoform 524.2 0.523 0.323 2.835 Bromomethane 502.2 ELCD 0.178 0.037 26.202 Bromomethane 524.2 0.810 0.893 3.516 Cadmium 1620 0.619 1.056 1.449 Cadmium 200.8 1.769 2.985 2.793 Calcium 1620 0.975 1.971 1.080 Carbon Disulfide 524.2 0.582  1.199 7.610 Carbon Tetrachloride 524.2 0.711  0.770 6.751 Carbontet+ 1,1 dcp 502.2 ELCD 0.986 2.089 2.162 Chloroacetonitrile 524.2 0.841 1.671 1.671 Chlorobenzene 502.2 ELCD 1.373 2.964 38.584 Chlorobenzene 502.2 PID 2.654 5.904 2.063 Chlorobenzene 524.2 0.880 0.643 4.864 Chloroethane 502.2 ELCD 0.051 0.041 23.132 Chloroethane 524.2 0.619 0.637 5.069 Chloroform 502.2 ELCD 9.595 17.716 0.722 Chloroform 524.2 0.745 0.692 5.610 Chloromethane 502.2 ELCD 1.292 3.452 2.934 Chloromethane 524.2 0.803 1.469 4.798 Chromium 1620 0.819 1.246 1.545 Chromium 200.8 0.847 1.713 5.391 Cis 1,2 dce+ 2,2 dcp 502.2 ELCD 1.334 2.619 3.344 Table 3. Ratios of Detection Limits to the EPA/ ACS DL for the Episode 6000 Dataset Analyte Method Procedure ISO CRV/ MDL ISO MDV/ MDL SL IDE/ MDL Draft Document for Peer Review  Do Not Circulate  August 2002 C 21 Cis 1,2 dichloroethene 524.2 0.826  0.342 5.104 Cis 1,3 dichloropropene 502.2 ELCD 2.183 4.379 8.267 Cis 1,3 dichloropropene 502.2 PID 0.839 1.742 1.367 Cis 1,3 dichloropropene 524.2 0.616 0.038 4.116 Cobalt 1620 0.409 0.824 1.585 Cobalt 200.8 0.790  64.641 8.058 Copper 1620 0.825 1.739 3.362 Copper 200.8 0.716 1.429 20.667 Dibromochloromethane 502.2 ELCD 2.077 4.211 45.610 Dibromochloromethane 524.2 0.600 0.208 4.953 Dibromomethane 502.2 ELCD 7.153 14.604 67.146 Dibromomethane 524.2 0.806 1.145 3.356 Dichlorodifluoromethane 502.2 ELCD 163.453 192.935 9.771 Dichlorodifluoromethane 524.2 0.651 0.551 5.027 Diethyl Ether 524.2 0.952 1.412 2.837 Ethyl Methacrylate 524.2 0.681 0.401 5.391 Ethylbenzene 502.2 PID 2.459 5.663 3.496 Ethylbenzene 524.2 0.833  0.475 4.992 Hardness 130.2 0.669 1.391 2.598 Hexachlorobutadiene 502.2 ELCD 5.586 11.673 2.097 Hexachlorobutadiene 524.2 0.519  0.293 3.866 Hexachloroethane 524.2 0.883 0.782 4.186 Hexchlobutadiene+ naphthalene 502.2 PID 1.423 3.208 0.920 Iron 1620 2.991 5.223 3.824 Isopropylbenzene 502.2 PID 2.530 5.930 2.921 Isopropylbenzene 524.2 0.920 1.099 10.555 Lead 1620 0.720 1.193 1.407 Lead 200.8 0.093 0.183 0.301 M+ p Xylene 502.2 PID 1.093 2.496 1.281 M+ p Xylene 524.2 0.588 0.449 9.870 Magnesium 1620 0.861 1.702 0.967 Manganese 1620 0.158 0.378 0.953 Manganese 200.8 0.974 1.587 3.450 Mercury 200.8 0.799  4.048 14.165 Table 3. Ratios of Detection Limits to the EPA/ ACS DL for the Episode 6000 Dataset Analyte Method Procedure ISO CRV/ MDL ISO MDV/ MDL SL IDE/ MDL Draft Document for Peer Review  Do Not Circulate  August 2002 C 22 Methacrylonitrile 524.2 0.642 1.034 1.808 Methyl Iodide 524.2 0.924  0.257 6.826 Methyl Tert butyl Ether 524.2 0.630  1.011 7.514 Methylacrylate 524.2 0.918 1.618 2.495 Methylene Chloride 502.2 ELCD 14.312 39.130 21.261 Methylene Chloride 524.2 0.875 1.196 3.367 Methylmethacrylate 524.2 0.376 0.535 2.153 Molybdenum 1620 0.698 1.543 1.188 Molybdenum 200.8 0.777 0.013 68.949 N butylbenzene 502.2 PID 2.322 5.050 4.676 N butylbenzene 524.2 0.890 1.694 8.614 N propylbenzene 502.2 PID 14.846 33.306 2.221 N propylbenzene 524.2 0.676  1.102 6.104 Naphthalene 524.2 0.821 0.983 3.622 Nickel 1620 0.656 1.271 1.176 Nickel 200.8 0.397 0.736 0.524 o xylene 524.2 0.802  1.396 8.734 o xylene+ styrene 502.2 PID 2.012 4.469 1.893 P isoproptol+ 1,4 dcb 502.2 PID 2.090 4.573 2.107 Pentachloroethane 524.2 0.035  0.153 0.610 Sec butylbenzene 502.2 PID 1.039 2.402 1.429 Sec butylbenzene 524.2 0.762  0.517 9.507 Selenium 1620 0.729 1.759 2.256 Selenium 200.8 0.815 1.577 2.139 Silver 1620 0.731 1.324 2.082 Silver 200.8 0.441 0.947 2.581 Sodium 1620 0.713 1.404 1.913 Styrene 524.2 0.797 0.815 8.467 Tert butylbenzene 502.2 PID 2.024 4.819 2.575 Tert butylbenzene 524.2 0.535 1.065 7.707 Tetrachloroethene 502.2 ELCD 11.204 23.979 2.831 Tetrachloroethene 502.2 PID 5.175 12.216 2.540 Tetrachloroethene 524.2 0.997 0.688 4.482 Thallium 1620 1.273 2.747 2.361 Table 3. Ratios of Detection Limits to the EPA/ ACS DL for the Episode 6000 Dataset Analyte Method Procedure ISO CRV/ MDL ISO MDV/ MDL SL IDE/ MDL Draft Document for Peer Review  Do Not Circulate  August 2002 C 23 Thallium 200.8 1.038 1.964 3.125 Thorium 200.8 0.836  6.702 4.345 Tin 1620 0.550 0.856 0.327 Titanium 1620 0.932 1.685 1.097 Toluene 502.2 PID 0.923 2.068 0.873 Toluene 524.2 0.280  0.100 6.591 Total Phosphorus 365.2 0.777 1.572 2.202 Total Suspended Solids 160.2 0.810 1.662 2.459 Trans 1,2 dichloroethene 502.2 ELCD 4.267 9.382 1.603 Trans 1,2 dichloroethene 524.2 0.834  0.210 6.695 Trans 1,3 dichloropropene 502.2 ELCD 1.098 2.183 6.938 Trans 1,3 dichloropropene 502.2 PID 0.641 1.358 1.454 Trans 1,3 dichloropropene 524.2 0.486  0.008 4.018 Trans 1,4 dichloro 2 butene 524.2 0.680 1.150 2.310 Trichloroethene 502.2 ELCD 1.157 2.435 4.169 Trichloroethene 502.2 PID 1.592 3.635 3.539 Trichloroethene 524.2 0.952 1.009 4.690 Trichlorofluoromethane 502.2 ELCD 0.114 0.256 18.504 Trichlorofluoromethane 524.2 0.858 0.527 3.516 Uranium 200.8 0.495 0.757 2.519 Vanadium 1620 0.573 1.138 1.370 Vanadium 200.8 0.923 1.791 1.522 Vinyl Chloride 502.2 ELCD 0.144 0.268 13.063 Vinyl Chloride 524.2 0.719 0.004 6.845 WAD Cyanide 1677 0.296 0.558 1.175 Xylene ( Total) 524.2 0.575 0.850 12.430 Yttrium 1620 0.712 1.310 1.622 Zinc 1620 0.886 1.423 1.700 Zinc 200.8 0.511 0.895 1.663 Note: ELCD or PID in the Procedure column indicates the photo ionization detector ( PID) or electrolytic conductivity detector ( ELCD) in EPA Method 502.2 Draft Document for Peer Review  Do Not Circulate  August 2002 C 24 Summary Statistics for Table 3 ISO CRV/ EPA/ ACS DL ISO MDV/ EPA/ ACS DL SL IDE/ EPA/ ACS DL Minimum 0.01  64.64 0.10 25th percentile 0.61 0.52 1.60 Median 0.80 1.17 2.86 75th percentile 1.08 2.17 5.41 Maximum 163.45 192.93 242.50 Number of analytes Percent of analytes p value for percent= 50 CRV> DL 52 26.26% < 0.0001 MDV> DL 113 57.07% 0.055 SL IDE> DL 181 91.41% < 0.0001 Table 4. Comparison Quantitation Limits for the Episode 6000 Dataset ( µ g/ L except where footnoted)

Analyte Method Procedure EPA/ ACS QL ISO/ IUPAC LOQ ASTM SL IQE 1,1,1,2 tetrachloroethane 502.2 ELCD 0.2 0.152 0.030 1,1,1,2 tetrachloroethane 524.2 0.2 0.183 0.181 1,1,1 trichloroethane 502.2 ELCD 0.1 0.044 0.830 1,1,1 trichloroethane 524.2 0.5 0.102 0.240 1,1,2,2 tce+ 1,2,3 tcp 502.2 ELCD 0.5 1.110 5.514 1,1,2,2 tetrachloroethane 524.2 0.5 0.596 0.569 1,1,2 trichloroethane 502.2 ELCD 0.1 0.289 0.060 1,1,2 trichloroethane 524.2 0.5 0.212 0.290 1,1 dichloroethane 502.2 ELCD 0.05 0.047 0.527 1,1 dichloroethane 524.2 0.2 0.099 0.115 1,1 dichloroethene 502.2 ELCD 0.1 0.096 3.796 1,1 dichloroethene 524.2 0.2 0.159 0.129 1,1 dichloropropanone 524.2 20 15.396 12.705 1,1 dichloropropene 524.2 0.5 0.057 0.180 1,2,3 trichlorobenzene 502.2 ELCD 0.2 1.750 0.851 1,2,3 trichlorobenzene 502.2 PID 0.2 1.818 0.248 1,2,3 trichlorobenzene 524.2 0.2 0.192 0.216 1,2,3 trichloropropane 524.2 20 0.267 11.316 1,2,4 trichlorobenzene 502.2 ELCD 0.1 1.150 0.401 Table 4. Comparison Quantitation Limits for the Episode 6000 Dataset ( µ g/ L except where footnoted)

Analyte Method Procedure EPA/ ACS QL ISO/ IUPAC LOQ ASTM SL IQE Draft Document for Peer Review  Do Not Circulate  August 2002 C 25 1,2,4 trichlorobenzene 502.2 PID 0.2 1.371 0.439 1,2,4 trichlorobenzene 524.2 0.2 0.231 0.141 1,2,4 trimethylbenzene 502.2 PID 0.5 0.485 0.653 1,2,4 trimethylbenzene 524.2 0.1 0.050 20.896 1,2 dibromo 3 chloropropane 524.2 10 1.843 71.182 1,2 dibromoethane 502.2 ELCD 0.5 0.156 0.592 1,2 dibromoethane 524.2 0.5 0.560 0.417 1,2 dichlorobenzene 502.2 ELCD 0.1 0.418 0.183 1,2 dichlorobenzene 502.2 PID 0.1 0.139 0.346 1,2 dichlorobenzene 524.2 0.1 0.101 0.085 1,2 dichloroethane 502.2 ELCD 0.1 0.089 0.065 1,2 dichloroethane 524.2 0.5 0.122 0.222 1,2 dichloropropane 502.2 ELCD 0.1 1.138 0.102 1,2 dichloropropane 524.2 0.5 0.148 0.196 1,3,5 tmb+ 4 chlorotoluene 502.2 PID 0.2 1.275 0.189 1,3,5 trimethylbenzene 524.2 0.1 0.044 23.744 1,3 dichlorobenzene 502.2 ELCD 0.1 0.301 0.936 1,3 dichlorobenzene 502.2 PID 0.2 0.840 0.465 1,3 dichlorobenzene 524.2 0.1 0.080 0.076 1,3 dichloropropane 502.2 ELCD 0.1 0.356 0.054 1,3 dichloropropane 524.2 0.2 0.114 0.139 1,4 dichlorobenzene 502.2 ELCD 0.1 0.571 0.101 1,4 dichlorobenzene 524.2 0.1 0.069 0.078 1 chlorobutane 524.2 0.1 0.082 29.943 2,2 dichloropropane 524.2 10 0.568 38.009 2 butanone 524.2 2 1.416 0.893 2 chlorotoluene 502.2 ELCD 0.5 0.881 0.493 2 chlorotoluene 502.2 PID 1 2.877 0.849 2 chlorotoluene 524.2 0.1 0.046 0.053 2 hexanone 524.2 10 0.669 0.442 2 nitropropane 524.2 10 1.280 0.590 4 chlorotoluene 502.2 ELCD 0.5 0.668 0.142 1 4 chlorotoluene 524.2 0.1 0.037 23.810 4 isopropyltoluene 524.2 0.1 0.043 0.016 Table 4. Comparison Quantitation Limits for the Episode 6000 Dataset ( µ g/ L except where footnoted)

Analyte Method Procedure EPA/ ACS QL ISO/ IUPAC LOQ ASTM SL IQE Draft Document for Peer Review  Do Not Circulate  August 2002 C 26 4 methyl 2 pentanone 524.2 5 2.065 1.785 Acetone 524.2 2 2.115 2.741 Acrylonitrile 524.2 5 1.816 28.056 Allyl Chloride 524.2 0.2 0.129 29.674 Aluminum 1620 100 76.242 464.069 Aluminum 200.8 50 9.418 29.684 Ammonia as Nitrogen 2 350.3 0.05 0.037 0.035 Antimony 1620 5 4.784 9.551 Antimony 200.8 0.5 0.017 0.034 Arsenic 1620 5 3.684 3.097 Arsenic 200.8 1 0.720 0.798 Barium 1620 5 4.722 4.118 Barium 200.8 0.1 0.161 0.211 Benzene 502.2 PID 0.1 0.273 0.182 Benzene 524.2 0.05 0.075 0.044 Beryllium 1620 2 1.055 0.980 Beryllium 200.8 0.02 0.018 0.044 Boron 1620 100 46.040 51.134 Bromobenzene 502.2 ELCD 0.5 0.593 3.529 Bromobenzene 502.2 PID 0.05 1.767 0.100 Bromobenzene 524.2 0.2 0.167 0.140 Bromochloromethane 502.2 ELCD 0.1 0.090 1.598 Bromochloromethane 524.2 0.5 0.549 0.368 Bromodichloromethane 502.2 ELCD 0.05 0.091 0.424 Bromodichloromethane 524.2 0.2 0.135 0.128 Bromoform 502.2 ELCD 0.2 0.056 3.393 Bromoform 524.2 0.5 0.287 0.482 Bromomethane 502.2 ELCD 1 undefined 3 16.351 Bromomethane 524.2 0.2 0.252 0.226 Cadmium 1620 0.5 0.346 0.410 Cadmium 200.8 0.02 0.046 0.063 Calcium 1620 100 186.530 99.975 Carbon Disulfide 524.2 0.1 0.077 0.101 Carbon Tetrachloride 524.2 0.2 0.127 0.140 Table 4. Comparison Quantitation Limits for the Episode 6000 Dataset ( µ g/ L except where footnoted)

Analyte Method Procedure EPA/ ACS QL ISO/ IUPAC LOQ ASTM SL IQE Draft Document for Peer Review  Do Not Circulate  August 2002 C 27 Carbontet+ 1,1 dcp 502.2 ELCD 0.2 0.173 0.069 Chloroacetonitrile 524.2 10 4.169 3.310 Chlorobenzene 502.2 ELCD 0.1 0.092 1.766 Chlorobenzene 502.2 PID 0.1 0.504 0.119 Chlorobenzene 524.2 0.1 0.108 0.059 Chloroethane 502.2 ELCD 0.5 0.037 5.826 Chloroethane 524.2 0.5 0.185 0.255 Chloroform 502.2 ELCD 0.2 2.217 0.025 Chloroform 524.2 0.2 0.138 0.121 Chloromethane 502.2 ELCD 0.2 0.709 1.734 Chloromethane 524.2 0.2 0.181 0.141 Chromium 1620 1 0.993 1.259 Chromium 200.8 0.2 0.331 1.028 Cis 1,2 dce+ 2,2 dcp 502.2 ELCD 0.05 0.097 0.039 Cis 1,2 dichloroethene 524.2 0.5 0.154 0.144 Cis 1,3 dichloropropene 502.2 ELCD 0.1 0.090 0.415 Cis 1,3 dichloropropene 502.2 PID 0.2 0.254 0.017 1 Cis 1,3 dichloropropene 524.2 0.2 0.116 0.141 Cobalt 1620 50 20.916 40.837 Cobalt 200.8 0.005 undefined 3 undefined 4 Copper 1620 20 27.513 47.509 Copper 200.8 0.1 0.142 1.825 Dibromochloromethane 502.2 ELCD 0.1 0.106 1.252 Dibromochloromethane 524.2 0.5 0.149 0.288 Dibromomethane 502.2 ELCD 0.1 0.257 1.395 Dibromomethane 524.2 0.5 0.400 0.460 Dichlorodifluoromethane 502.2 ELCD 0.1 5.759 1.091 Dichlorodifluoromethane 524.2 0.5 0.289 0.480 Diethyl Ether 524.2 0.5 0.563 0.404 Ethyl Methacrylate 524.2 0.5 0.139 0.183 Ethylbenzene 502.2 PID 0.1 0.341 0.157 Ethylbenzene 524.2 0.2 0.123 0.077 Hardness 2 130.2 2 2.973 5.465 Hexachlorobutadiene 502.2 ELCD 0.2 1.466 0.243 Table 4. Comparison Quantitation Limits for the Episode 6000 Dataset ( µ g/ L except where footnoted)

Analyte Method Procedure EPA/ ACS QL ISO/ IUPAC LOQ ASTM SL IQE Draft Document for Peer Review  Do Not Circulate  August 2002 C 28 Hexachlorobutadiene 524.2 0.2 0.160 0.228 Hexachloroethane 524.2 0.2 0.232 0.167 Hexchlobutadiene+ naphthalene 502.2 PID 2 6.108 1.542 Iron 1620 200 1490.589 996.565 Isopropylbenzene 502.2 PID 0.1 0.337 0.129 Isopropylbenzene 524.2 0.1 0.056 25.592 Lead 1620 5 5.062 5.698 Lead 200.8 2 0.318 0.685 M+ p Xylene 502.2 PID 0.2 0.652 0.222 M+ p Xylene 524.2 0.1 0.042 24.651 Magnesium 1620 500 454.043 267.199 Manganese 1620 20 7.948 15.264 Manganese 200.8 0.1 0.133 0.245 Mercury 200.8 0.02 0.056 0.039 Methacrylonitrile 524.2 2 1.065 19.062 Methyl Iodide 524.2 0.2 0.108 0.083 Methyl Tert butyl Ether 524.2 0.5 0.073 0.122 Methylacrylate 524.2 1 0.966 0.727 Methylene Chloride 502.2 ELCD 1 undefined 3 6.033 Methylene Chloride 524.2 0.2 0.354 0.433 Methylmethacrylate 524.2 1 0.381 20.773 Molybdenum 1620 10 9.752 7.597 Molybdenum 200.8 0.01 0.052 0.608 N butylbenzene 502.2 PID 0.1 0.429 0.745 N butylbenzene 524.2 0.1 0.077 0.067 N propylbenzene 502.2 PID 0.2 3.869 0.186 N propylbenzene 524.2 0.2 0.110 29.878 Naphthalene 524.2 0.2 0.184 0.108 Nickel 1620 100 66.486 67.206 Nickel 200.8 0.5 0.287 0.183 o xylene 524.2 0.2 0.062 0.040 o xylene+ styrene 502.2 PID 0.2 0.746 0.181 P isoproptol+ 1,4 dcb 502.2 PID 0.2 0.956 0.456 Pentachloroethane 524.2 2 0.086 0.551 Table 4. Comparison Quantitation Limits for the Episode 6000 Dataset ( µ g/ L except where footnoted)

Analyte Method Procedure EPA/ ACS QL ISO/ IUPAC LOQ ASTM SL IQE Draft Document for Peer Review  Do Not Circulate  August 2002 C 29 Sec butylbenzene 502.2 PID 0.2 0.377 0.157 Sec butylbenzene 524.2 0.1 0.063 0.047 Selenium 1620 2 3.859 5.235 Selenium 200.8 1 0.805 1.045 Silver 1620 20 16.734 25.842 Silver 200.8 0.02 0.011 0.056 Sodium 1620 200 251.546 337.755 Styrene 524.2 0.1 0.054 0.041 Tert butylbenzene 502.2 PID 0.1 0.391 0.203 Tert butylbenzene 524.2 0.1 0.063 0.073 Tetrachloroethene 502.2 ELCD 0.1 1.226 0.122 Tetrachloroethene 502.2 PID 0.2 2.084 0.750 Tetrachloroethene 524.2 0.2 0.377 30.554 Thallium 1620 2 3.748 2.799 Thallium 200.8 0.001 0.002 0.003 Thorium 200.8 0.002 0.005 0.004 Tin 1620 10 9.237 9.406 Titanium 1620 20 20.807 14.236 Toluene 502.2 PID 0.2 0.409 0.194 Toluene 524.2 0.2 0.028 0.046 Total Phosphorus 2 365.2 0.02 0.024 0.030 Total Suspended Solids 2 160.2 5 5.011 6.729 Trans 1,2 dichloroethene 502.2 ELCD 0.2 1.060 0.191 Trans 1,2 dichloroethene 524.2 0.2 0.140 0.153 Trans 1,3 dichloropropene 502.2 ELCD 0.1 0.073 0.729 Trans 1,3 dichloropropene 502.2 PID 0.2 0.205 0.175 Trans 1,3 dichloropropene 524.2 0.5 0.121 0.218 Trans 1,4 dichloro 2 butene 524.2 2 1.801 30.108 Trichloroethene 502.2 ELCD 0.1 0.081 3.169 Trichloroethene 502.2 PID 0.1 0.260 0.401 Trichloroethene 524.2 0.2 0.283 0.167 Trichlorofluoromethane 502.2 ELCD 0.5 0.085 4.662 Trichlorofluoromethane 524.2 0.5 0.279 42.490 Uranium 200.8 0.001 0.001 0.002 Table 4. Comparison Quantitation Limits for the Episode 6000 Dataset ( µ g/ L except where footnoted)

Analyte Method Procedure EPA/ ACS QL ISO/ IUPAC LOQ ASTM SL IQE Draft Document for Peer Review  Do Not Circulate  August 2002 C 30 Vanadium 1620 20 21.586 24.338 Vanadium 200.8 2 2.627 1.933 Vinyl Chloride 502.2 ELCD 1 0.270 8.234 Vinyl Chloride 524.2 0.2 0.139 0.219 WAD Cyanide 1677 2 0.852 1.624 Xylene ( Total) 524.2 0.1 0.027 23.520 Yttrium 1620 5 6.571 8.962 Zinc 1620 10 9.575 10.452 Zinc 200.8 2 2.147 7.024 1 IQE 10% undefined, IQE 20% reported 2 Results reported as mg/ L 3 No LOQ could be calculated due to a square root of a negative number in the formula 4 IQE 10%, IQE 20% and IQE 30% all negative based on chosen model ( linear) Note: ELCD or PID in the Procedure column indicates the photo ionization detector ( PID) or electrolytic conductivity detector ( ELCD) in EPA Method 502.2 Table 5. Ratios of Quantitation Limits to the EPA/ ACS QL for the Episode 6000 Dataset Analyte Method Procedure ISO LOQ/ ML SL IQE/ ML 1,1,1,2 tetrachloroethane 502.2 ELCD 0.759 0.152 1,1,1,2 tetrachloroethane 524.2 0.915 0.907 1,1,1 trichloroethane 502.2 ELCD 0.445 8.298 1,1,1 trichloroethane 524.2 0.203 0.479 1,1,2,2 tce+ 1,2,3 tcp 502.2 ELCD 2.220 11.027 1,1,2,2 tetrachloroethane 524.2 1.192 1.138 1,1,2 trichloroethane 502.2 ELCD 2.886 0.603 1,1,2 trichloroethane 524.2 0.424 0.579 1,1 dichloroethane 502.2 ELCD 0.949 10.531 1,1 dichloroethane 524.2 0.496 0.573 1,1 dichloroethene 502.2 ELCD 0.960 37.963 1,1 dichloroethene 524.2 0.795 0.644 1,1 dichloropropanone 524.2 0.770 0.635 1,1 dichloropropene 524.2 0.114 0.360 1,2,3 trichlorobenzene 502.2 ELCD 8.751 4.257 1,2,3 trichlorobenzene 502.2 PID 9.092 1.239 Table 5. Ratios of Quantitation Limits to the EPA/ ACS QL for the Episode 6000 Dataset Analyte Method Procedure ISO LOQ/ ML SL IQE/ ML Draft Document for Peer Review  Do Not Circulate  August 2002 C 31 1,2,3 trichlorobenzene 524.2 0.959 1.080 1,2,3 trichloropropane 524.2 0.013 0.566 1,2,4 trichlorobenzene 502.2 ELCD 11.502 4.010 1,2,4 trichlorobenzene 502.2 PID 6.853 2.197 1,2,4 trichlorobenzene 524.2 1.157 0.703 1,2,4 trimethylbenzene 502.2 PID 0.970 1.306 1,2,4 trimethylbenzene 524.2 0.503 208.956 1,2 dibromo 3 chloropropane 524.2 0.184 7.118 1,2 dibromoethane 502.2 ELCD 0.311 1.185 1,2 dibromoethane 524.2 1.119 0.834 1,2 dichlorobenzene 502.2 ELCD 4.178 1.833 1,2 dichlorobenzene 502.2 PID 1.393 3.455 1,2 dichlorobenzene 524.2 1.006 0.848 1,2 dichloroethane 502.2 ELCD 0.891 0.650 1,2 dichloroethane 524.2 0.244 0.443 1,2 dichloropropane 502.2 ELCD 11.378 1.023 1,2 dichloropropane 524.2 0.296 0.393 1,3,5 tmb+ 4 chlorotoluene 502.2 PID 6.373 0.946 1,3,5 trimethylbenzene 524.2 0.436 237.442 1,3 dichlorobenzene 502.2 ELCD 3.008 9.356 1,3 dichlorobenzene 502.2 PID 4.201 2.326 1,3 dichlorobenzene 524.2 0.800 0.760 1,3 dichloropropane 502.2 ELCD 3.560 0.539 1,3 dichloropropane 524.2 0.569 0.695 1,4 dichlorobenzene 502.2 ELCD 5.714 1.010 1,4 dichlorobenzene 524.2 0.686 0.784 1 chlorobutane 524.2 0.823 299.428 2,2 dichloropropane 524.2 0.057 3.801 2 butanone 524.2 0.708 0.446 2 chlorotoluene 502.2 ELCD 1.763 0.986 2 chlorotoluene 502.2 PID 2.877 0.849 2 chlorotoluene 524.2 0.463 0.533 2 hexanone 524.2 0.067 0.044 2 nitropropane 524.2 0.128 0.059 Table 5. Ratios of Quantitation Limits to the EPA/ ACS QL for the Episode 6000 Dataset Analyte Method Procedure ISO LOQ/ ML SL IQE/ ML Draft Document for Peer Review  Do Not Circulate  August 2002 C 32 4 chlorotoluene 502.2 ELCD 1.335 0.284 4 chlorotoluene 524.2 0.373 238.097 4 isopropyltoluene 524.2 0.428 0.163 4 methyl 2 pentanone 524.2 0.413 0.357 Acetone 524.2 1.057 1.371 Acrylonitrile 524.2 0.363 5.611 Allyl chloride 524.2 0.646 148.372 Aluminum 1620 0.762 4.641 Aluminum 200.8 ICP/ MS 0.188 0.594 Ammonia as nitrogen 350.3 0.733 0.709 Antimony 1620 0.957 1.910 Antimony 200.8 ICP/ MS 0.035 0.067 Arsenic 1620 0.737 0.619 Arsenic 200.8 ICP/ MS 0.720 0.798 Barium 1620 0.944 0.824 Barium 200.8 ICP/ MS 1.608 2.114 Benzene 502.2 PID 2.735 1.819 Benzene 524.2 1.509 0.877 Beryllium 1620 0.527 0.490 Beryllium 200.8 ICP/ MS 0.905 2.201 Boron 1620 0.460 0.511 Bromobenzene 502.2 ELCD 1.186 7.058 Bromobenzene 502.2 PID 35.338 2.007 Bromobenzene 524.2 0.833 0.699 Bromochloromethane 502.2 ELCD 0.900 15.977 Bromochloromethane 524.2 1.097 0.737 Bromodichloromethane 502.2 ELCD 1.814 8.484 Bromodichloromethane 524.2 0.676 0.640 Bromoform 502.2 ELCD 0.282 16.964 Bromoform 524.2 0.573 0.964 Bromomethane 502.2 ELCD N/ A 16.351 Bromomethane 524.2 1.262 1.130 Cadmium 1620 0.692 0.820 Cadmium 200.8 ICP/ MS 2.311 3.148 Table 5. Ratios of Quantitation Limits to the EPA/ ACS QL for the Episode 6000 Dataset Analyte Method Procedure ISO LOQ/ ML SL IQE/ ML Draft Document for Peer Review  Do Not Circulate  August 2002 C 33 Calcium 1620 1.865 1.000 Carbon disulfide 524.2 0.768 1.013 Carbon tetrachloride 524.2 0.635 0.700 Carbontet+ 1,1 dcp 502.2 ELCD 0.864 0.343 Chloroacetonitrile 524.2 0.417 0.331 Chlorobenzene 502.2 ELCD 0.921 17.658 Chlorobenzene 502.2 PID 5.040 1.190 Chlorobenzene 524.2 1.077 0.595 Chloroethane 502.2 ELCD 0.074 11.652 Chloroethane 524.2 0.369 0.510 Chloroform 502.2 ELCD 11.086 0.126 Chloroform 524.2 0.688 0.606 Chloromethane 502.2 ELCD 3.547 8.669 Chloromethane 524.2 0.906 0.703 Chromium 1620 0.993 1.259 Chromium 200.8 ICP/ MS 1.653 5.142 Cis 1,2 dce+ 2,2 dcp 502.2 ELCD 1.941 0.780 Cis 1,2 dichloroethene 524.2 0.307 0.288 Cis 1,3 dichloropropene 502.2 ELCD 0.902 4.151 Cis 1,3 dichloropropene 502.2 PID 1.271 0.083 Cis 1,3 dichloropropene 524.2 0.582 0.706 Cobalt 1620 0.418 0.817 Cobalt 200.8 ICP/ MS N/ A N/ A Copper 1620 1.376 2.375 Copper 200.8 ICP/ MS 1.419 18.250 Dibromochloromethane 502.2 ELCD 1.059 12.515 Dibromochloromethane 524.2 0.299 0.575 Dibromomethane 502.2 ELCD 2.572 13.949 Dibromomethane 524.2 0.800 0.920 Dichlorodifluoromethane 502.2 ELCD 57.590 10.907 Dichlorodifluoromethane 524.2 0.579 0.959 Diethyl ether 524.2 1.126 0.808 Ethyl methacrylate 524.2 0.279 0.366 Ethylbenzene 502.2 PID 3.413 1.573 Table 5. Ratios of Quantitation Limits to the EPA/ ACS QL for the Episode 6000 Dataset Analyte Method Procedure ISO LOQ/ ML SL IQE/ ML Draft Document for Peer Review  Do Not Circulate  August 2002 C 34 Ethylbenzene 524.2 0.613 0.387 Hardness 130.2 1.487 2.733 Hexachlorobutadiene 502.2 ELCD 7.332 1.215 Hexachlorobutadiene 524.2 0.799 1.142 Hexachloroethane 524.2 1.159 0.837 Hexchlobutadiene+ naphthalene 502.2 PID 3.054 0.771 Iron 1620 7.453 4.983 Isopropylbenzene 502.2 PID 3.372 1.290 Isopropylbenzene 524.2 0.563 255.921 Lead 1620 1.012 1.140 Lead 200.8 ICP/ MS 0.159 0.342 M+ p xylene 502.2 PID 3.262 1.112 M+ p xylene 524.2 0.419 246.513 Magnesium 1620 0.908 0.534 Manganese 1620 0.397 0.763 Manganese 200.8 ICP/ MS 1.326 2.451 Mercury 200.8 ICP/ MS 2.781 1.933 Methacrylonitrile 524.2 0.533 9.531 Methyl iodide 524.2 0.538 0.417 Methyl tert butyl ether 524.2 0.146 0.245 Methylacrylate 524.2 0.966 0.727 Methylene chloride 502.2 ELCD N/ A 6.033 Methylene chloride 524.2 1.769 2.164 Methylmethacrylate 524.2 0.381 20.773 Molybdenum 1620 0.975 0.760 Molybdenum 200.8 ICP/ MS 5.181 60.817 N butylbenzene 502.2 PID 4.290 7.453 N butylbenzene 524.2 0.767 0.673 N propylbenzene 502.2 PID 19.343 0.931 N propylbenzene 524.2 0.552 149.392 Naphthalene 524.2 0.921 0.541 Nickel 1620 0.665 0.672 Nickel 200.8 ICP/ MS 0.574 0.365 O xylene 524.2 0.310 0.202 Table 5. Ratios of Quantitation Limits to the EPA/ ACS QL for the Episode 6000 Dataset Analyte Method Procedure ISO LOQ/ ML SL IQE/ ML Draft Document for Peer Review  Do Not Circulate  August 2002 C 35 O xylene+ styrene 502.2 PID 3.731 0.905 P isoproptol+ 1,4 dcb 502.2 PID 4.778 2.281 Pentachloroethane 524.2 0.043 0.276 Sec butylbenzene 502.2 PID 1.885 0.784 Sec butylbenzene 524.2 0.628 0.475 Selenium 1620 1.929 2.617 Selenium 200.8 ICP/ MS 0.805 1.045 Silver 1620 0.837 1.292 Silver 200.8 ICP/ MS 0.543 2.800 Sodium 1620 1.258 1.689 Styrene 524.2 0.536 0.407 Tert butylbenzene 502.2 PID 3.911 2.027 Tert butylbenzene 524.2 0.634 0.735 Tetrachloroethene 502.2 ELCD 12.264 1.217 Tetrachloroethene 502.2 PID 10.419 3.749 Tetrachloroethene 524.2 1.886 152.769 Thallium 1620 1.874 1.399 Thallium 200.8 ICP/ MS 2.085 3.286 Thorium 200.8 ICP/ MS 2.648 2.198 Tin 1620 0.924 0.941 Titanium 1620 1.040 0.712 Toluene 502.2 PID 2.045 0.971 Toluene 524.2 0.138 0.228 Total phosphorus 365.2 1.188 1.499 Total suspended solids 160.2 1.002 1.346 Trans 1,2 dichloroethene 502.2 ELCD 5.298 0.953 Trans 1,2 dichloroethene 524.2 0.702 0.764 Trans 1,3 dichloropropene 502.2 ELCD 0.731 7.286 Trans 1,3 dichloropropene 502.2 PID 1.023 0.874 Trans 1,3 dichloropropene 524.2 0.241 0.436 Trans 1,4 dichloro 2 butene 524.2 0.900 15.054 Trichloroethene 502.2 ELCD 0.812 31.690 Trichloroethene 502.2 PID 2.601 4.010 Trichloroethene 524.2 1.417 0.837 Table 5. Ratios of Quantitation Limits to the EPA/ ACS QL for the Episode 6000 Dataset Analyte Method Procedure ISO LOQ/ ML SL IQE/ ML Draft Document for Peer Review  Do Not Circulate  August 2002 C 36 Trichlorofluoromethane 502.2 ELCD 0.171 9.325 Trichlorofluoromethane 524.2 0.558 84.980 Uranium 200.8 ICP/ MS 0.721 1.853 Vanadium 1620 1.079 1.217 Vanadium 200.8 ICP/ MS 1.314 0.966 Vinyl chloride 502.2 ELCD 0.270 8.234 Vinyl chloride 524.2 0.697 1.097 Wad cyanide 1677 WADCN 0.426 0.812 Xylene ( total) 524.2 0.266 235.197 Yttrium 1620 1.314 1.792 Zinc 1620 0.957 1.045 Zinc 200.8 ICP/ MS 1.073 3.512 Note: ELCD or PID in the Procedure column indicates the photo ionization detector ( PID) or electrolytic conductivity detector ( ELCD) in EPA Method 502.2 Summary Statistics for Table 5 ISO LOQ/ QL SL IQE/ QL Minimum 0.013 0.044 25th percentile 0.547 0.672 Median 0.915 1.023 75th percentile 1.792 3.512 Maximum 57.590 299.428 Number of analytes Percent of analytes p value for percent= 50 LOQ> QL 84 43.08% 0.062 SL IQE> QL 101 51.27% 0.776 Draft Document for Peer Review  Do Not Circulate  August 2002 C 37 Table 6. Frequency Comparisons for Lowest and Highest Detection and Quantitation Limits for the Episode 6000 Dataset Detection limits Rank EPA/ ACS DL ISO CRV ISO MDV ASTM SL IDE 1 ( lowest) 30.3% 49.5% 17.7% 2.5% 2 34.3% 33.3% 16.2% 16.2% 3 30.8% 17.2% 33.3% 18.7% 4 ( highest) 4.5% 0% 32.8% 62.6% Quantitation limits Rank EPA/ ACS QL No equivalent ISO LOQ ASTM SL IQE 1 ( lowest) 50.5%  25.8% 22.2% 2 33.8%  26.8% 37.9% 3 ( highest) 14.1%  46.0% 38.4%

Table 7. Detection and Quantitation Limits for EPA Methods 1631 and 1638 as Computed by EPA and by EPRI ( ng/ L)

Element1 Ambient WQC2 Detection limits Quantitation limits MDL in Method IDE computed by ML in Method IQE computed by EPA EPRI EPA EPRI Antimony 14000 9.7 140 110 20 270 270 Cadmium 370 25 150 150 100 540 380 Copper 2400 87 780 770 200 3800 3000 Lead 540 15 140 160 50 420 370 Mercury 12 0.2 0.5 0.43 0.5 0.55 1.6 Nickel 8200 330 220 130 1000 15000 330 Selenium 5000 450 760 600 1000 630 720 Silver 320 29 220  100 5500

Thallium 1700 7.9 27 20 20 87 50 Zinc 32000 140 1700 2100 500 21000 26100 1 Mercury determined by EPA Method 1631; all others by EPA Method 1638 2 Lowest ambient water quality criterion ( WQC) in the National Toxics Rule ( 40 CFR 131.36) Draft Document for Peer Review  Do Not Circulate  August 2002 C 38 Table 8. Comparison of Single laboratory IDEs resulting from all model types for EPA Methods 1631 and 1638 Analyte IDE, Based on Given Model Constant Linear Exponential Hybrid Antimony 2400  72 1 140 99 Cadmium 1200 120 150 140 Copper 2600 960 780 690 Lead 380 140 140 140 Mercury 8.1 0.059 0.79 0.50 Nickel 6600  37 1 220 110 Selenium 4300 680 760 500 Silver 2400 670 220 undefined 2 Thallium 220 21 27 16 Zinc 9600 1500 1700 1700 1 Negative due to negative intercept estimate in precision model. 2 IDE did not converge to a single value for estimated models.

Table 9. Comparison of 16 point and 5 point Single laboratory IDEs ( SL IDEs) for the Episode 6000 Dataset Analyte Method Procedure SL IDE ( 16) SL IDE ( 5) SL IDE( 16)/ SL IDE( 5) SL IDE 16 Model SL IDE 5 Model 1,1,1,2 tetrachloroethane 502.2 ELCD 0.028 0.011 2.616 Exponential Linear 1,1,1,2 tetrachloroethane 524.2 0.206 0.160 1.287 Exponential Exponential 1,1,1 trichloroethane 502.2 ELCD 0.035 0.035 0.974 Exponential Exponential 1,1,1 trichloroethane 524.2 0.268 0.033 8.033 Exponential Hybrid 1,1,2,2 tce+ 1,2,3 tcp 502.2 ELCD 0.170 3.404 0.050 Exponential Constant 1,1,2,2 tetrachloroethane 524.2 0.377 0.505 0.746 Exponential Exponential 1,1,2 trichloroethane 502.2 ELCD 0.026 0.012 2.158 Exponential Linear 1,1,2 trichloroethane 524.2 0.284 0.218 1.300 Exponential Exponential 1,1 dichloroethane 502.2 ELCD 0.066 0.022 2.971 Exponential Exponential 1,1 dichloroethane 524.2 0.206 0.089 2.310 Exponential Exponential 1,1 dichloroethene 502.2 ELCD 0.193 0.068 2.834 Exponential Exponential 1,1 dichloroethene 524.2 0.278 0.077 3.607 Exponential Hybrid 1,1 dichloropropanone 524.2 6.032 8.566 0.704 Exponential Exponential 1,1 dichloropropene 524.2 0.247 0.038 6.493 Exponential Constant 1 1,2,3 trichlorobenzene 502.2 ELCD 0.122 0.161 0.755 Exponential Constant Table 9. Comparison of 16 point and 5 point Single laboratory IDEs ( SL IDEs) for the Episode 6000 Dataset Analyte Method Procedure SL IDE ( 16) SL IDE ( 5) SL IDE( 16)/ SL IDE( 5) SL IDE 16 Model SL IDE 5 Model Draft Document for Peer Review  Do Not Circulate  August 2002 C 39 1,2,3 trichlorobenzene 502.2 PID 0.114 0.060 1.891 Exponential Exponential 1,2,3 trichlorobenzene 524.2 0.259 0.139 1.854 Exponential Exponential 1,2,3 trichloropropane 524.2 1.206 0.230 5.241 Exponential Constant 1 1,2,4 trichlorobenzene 502.2 ELCD 0.077 0.096 0.798 Exponential Constant 1,2,4 trichlorobenzene 502.2 PID 0.124 0.070 1.774 Exponential Exponential 1,2,4 trichlorobenzene 524.2 0.208 0.108 1.916 Exponential Exponential 1,2,4 trimethylbenzene 502.2 PID 0.123 0.137 0.897 Exponential Constant 1,2,4 trimethylbenzene 524.2 0.129 0.054 2.380 Exponential Exponential 1,2 dibromo 3 chloropropane 524.2 1.619 0.414 3.912 Exponential Hybrid 1,2 dibromoethane 502.2 ELCD 0.143 0.023 6.138 Exponential Linear 1,2 dibromoethane 524.2 0.289 0.302 0.958 Exponential Exponential 1,2 dichlorobenzene 502.2 ELCD 0.053 0.053 1.007 Exponential Linear 1,2 dichlorobenzene 502.2 PID 0.147 0.067 2.197 Exponential Exponential 1,2 dichlorobenzene 524.2 0.112 0.065 1.727 Exponential Exponential 1,2 dichloroethane 502.2 ELCD 0.037 0.018 2.054 Exponential Exponential 1,2 dichloroethane 524.2 0.229 0.201 1.139 Exponential Exponential 1,2 dichloropropane 502.2 ELCD 0.037 0.083 0.440 Exponential Constant 1,2 dichloropropane 524.2 0.221 0.206 1.072 Exponential Exponential 1,3,5 tmb+ 4 chlorotoluene 502.2 PID 0.108 0.135 0.797 Exponential Constant 1,3,5 trimethylbenzene 524.2 0.117 0.045 2.612 Exponential Exponential 1,3 dichlorobenzene 502.2 ELCD 0.100 0.590 0.169 Exponential Constant 1,3 dichlorobenzene 502.2 PID 0.123 0.189 0.654 Exponential Constant 1,3 dichlorobenzene 524.2 0.126 0.040 3.123 Exponential Exponential 1,3 dichloropropane 502.2 ELCD 0.045 0.218 0.204 Exponential Constant 1,3 dichloropropane 524.2 0.170 0.112 1.517 Exponential Exponential 1,4 dichlorobenzene 502.2 ELCD 0.054 0.039 1.388 Exponential Linear 1,4 dichlorobenzene 524.2 0.110 0.047 2.333 Exponential Exponential 1 chlorobutane 524.2 0.200 0.058 3.451 Exponential Linear 2,2 dichloropropane 524.2 0.700 0.117 5.985 Exponential Hybrid 2 butanone 524.2 0.775 1.261 0.615 Exponential Exponential 2 chlorotoluene 502.2 ELCD 0.184 0.104 1.776 Exponential Exponential 2 chlorotoluene 502.2 PID 0.222 0.391 0.568 Exponential Constant 2 chlorotoluene 524.2 0.121 0.036 3.343 Exponential Exponential 2 hexanone 524.2 0.815 0.782 1.042 Exponential Exponential Table 9. Comparison of 16 point and 5 point Single laboratory IDEs ( SL IDEs) for the Episode 6000 Dataset Analyte Method Procedure SL IDE ( 16) SL IDE ( 5) SL IDE( 16)/ SL IDE( 5) SL IDE 16 Model SL IDE 5 Model Draft Document for Peer Review  Do Not Circulate  August 2002 C 40 2 nitropropane 524.2 0.965 8.974 0.108 Exponential Constant 4 chlorotoluene 502.2 ELCD 0.159 0.138 1.153 Exponential Linear 4 chlorotoluene 524.2 0.102 0.039 2.648 Exponential Exponential 4 isopropyltoluene 524.2 0.102 0.037 2.762 Exponential Exponential 4 methyl 2 pentanone 524.2 1.060 0.987 1.074 Exponential Exponential Acetone 524.2 2.025 28.956 0.070 Exponential Constant Acrylonitrile 524.2 1.197 0.982 1.219 Exponential Exponential Allyl Chloride 524.2 0.203 0.070 2.915 Exponential Hybrid Aluminum 1620 198.565 70.438 2.819 Constant Constant Aluminum 200.8 12.004 21.862 0.549 Exponential Constant Ammonia as Nitrogen 350.3 0.013 0.038 0.336 Exponential Constant Antimony 1620 4.087 6.023 0.678 Constant Linear Antimony 200.8 0.018 0.293 0.062 Exponential Constant Arsenic 1620 1.463 2.175 0.672 Exponential Constant Arsenic 200.8 0.346 0.340 1.015 Exponential Exponential Barium 1620 1.762 1.558 1.131 Constant Constant Barium 200.8 0.079 0.071 1.120 Exponential Constant Benzene 502.2 PID 0.077 0.058 1.324 Exponential Exponential Benzene 524.2 0.115 0.030 3.907 Exponential Exponential Beryllium 1620 0.428 0.427 1.003 Exponential Exponential Beryllium 200.8 0.019 0.017 1.138 Exponential Constant Boron 1620 19.884 21.488 0.925 Exponential Exponential Bromobenzene 502.2 ELCD 0.729 0.343 2.122 Linear Exponential Bromobenzene 502.2 PID 0.048 0.025 1.947 Exponential Exponential Bromobenzene 524.2 0.175 0.156 1.125 Exponential Exponential Bromochloromethane 502.2 ELCD 0.462 0.029 15.797 Linear Exponential Bromochloromethane 524.2 0.309 0.396 0.780 Exponential Exponential Bromodichloromethane 502.2 ELCD 0.064 0.018 3.584 Exponential Exponential Bromodichloromethane 524.2 0.182 0.093 1.951 Exponential Exponential Bromoform 502.2 ELCD 1.450 0.023 62.020 Constant Linear Bromoform 524.2 0.350 0.247 1.417 Exponential Exponential Bromomethane 502.2 ELCD 6.993 0.731 9.569 Constant Exponential Bromomethane 524.2 0.238 0.148 1.610 Exponential Linear Cadmium 1620 0.184 0.200 0.922 Exponential Exponential Table 9. Comparison of 16 point and 5 point Single laboratory IDEs ( SL IDEs) for the Episode 6000 Dataset Analyte Method Procedure SL IDE ( 16) SL IDE ( 5) SL IDE( 16)/ SL IDE( 5) SL IDE 16 Model SL IDE 5 Model Draft Document for Peer Review  Do Not Circulate  August 2002 C 41 Cadmium 200.8 0.011 0.015 0.735 Exponential Constant Calcium 1620 39.651 51.207 0.774 Linear Constant Carbon Disulfide 524.2 0.203 0.083 2.440 Exponential Linear Carbon Tetrachloride 524.2 0.258 0.166 1.549 Exponential Linear Carbontet+ 1,1 dcp 502.2 ELCD 0.062 0.049 1.274 Exponential Exponential Chloroacetonitrile 524.2 1.535 1.842 0.833 Exponential Exponential Chlorobenzene 502.2 ELCD 0.440 0.044 9.900 Linear Exponential Chlorobenzene 502.2 PID 0.062 0.058 1.083 Exponential Exponential Chlorobenzene 524.2 0.119 0.035 3.378 Exponential Exponential Chloroethane 502.2 ELCD 2.492 0.090 27.544 Constant Linear Chloroethane 524.2 0.336 0.239 1.403 Exponential Exponential Chloroform 502.2 ELCD 0.031 0.008 3.923 Exponential Linear Chloroform 524.2 0.203 0.111 1.829 Exponential Exponential Chloromethane 502.2 ELCD 0.204 0.499 0.409 Exponential Constant Chloromethane 524.2 0.215 0.148 1.456 Exponential Exponential Chromium 1620 0.478 0.728 0.657 Exponential Constant Chromium 200.8 0.393 0.473 0.830 Linear Constant Cis 1,2 dce+ 2,2 dcp 502.2 ELCD 0.043 0.027 1.575 Exponential Exponential Cis 1,2 dichloroethene 524.2 0.203 0.181 1.123 Exponential Exponential Cis 1,3 dichloropropene 502.2 ELCD 0.059 0.015 3.860 Exponential Exponential Cis 1,3 dichloropropene 502.2 PID 0.077 0.104 0.743 Exponential Exponential Cis 1,3 dichloropropene 524.2 0.158 0.103 1.536 Exponential Exponential Cobalt 1620 15.560 11.825 1.316 Exponential Exponential Cobalt 200.8 0.008 0.000  133.113 Exponential Exponential Copper 1620 20.328 15.251 1.333 Constant Constant Copper 200.8 0.770 0.873 0.882 Constant Constant Dibromochloromethane 502.2 ELCD 0.418 0.380 1.098 Linear Constant Dibromochloromethane 524.2 0.253 0.192 1.315 Exponential Exponential Dibromomethane 502.2 ELCD 0.441 0.286 1.543 Linear Constant Dibromomethane 524.2 0.342 0.347 0.985 Exponential Exponential Dichlorodifluoromethane 502.2 ELCD 0.087 1.175 0.074 Exponential Constant Dichlorodifluoromethane 524.2 0.420 0.265 1.584 Exponential Exponential Diethyl Ether 524.2 0.340 0.314 1.082 Exponential Exponential Ethyl Methacrylate 524.2 0.244 0.243 1.003 Exponential Exponential Table 9. Comparison of 16 point and 5 point Single laboratory IDEs ( SL IDEs) for the Episode 6000 Dataset Analyte Method Procedure SL IDE ( 16) SL IDE ( 5) SL IDE( 16)/ SL IDE( 5) SL IDE 16 Model SL IDE 5 Model Draft Document for Peer Review  Do Not Circulate  August 2002 C 42 Ethylbenzene 502.2 PID 0.075 0.048 1.571 Exponential Exponential Ethylbenzene 524.2 0.167 0.111 1.504 Exponential Exponential Hardness 130.2 2.152 4.687 0.459 Exponential Constant Hexachlorobutadiene 502.2 ELCD 0.090 0.069 1.300 Exponential Linear Hexachlorobutadiene 524.2 0.263 0.208 1.265 Exponential Exponential Hexachloroethane 524.2 0.234 0.234 1.000 Exponential Exponential Hexchlobutadiene+ naphthalene 502.2 PID 0.598 0.567 1.055 Exponential Constant Iron 1620 345.686 1021.716 0.338 Linear Constant Isopropylbenzene 502.2 PID 0.059 0.038 1.551 Exponential Exponential Isopropylbenzene 524.2 0.113 0.036 3.137 Exponential Exponential Lead 1620 2.317 2.831 0.819 Exponential Constant Lead 200.8 0.197 2.771 0.071 Exponential Constant M+ p Xylene 502.2 PID 0.116 0.114 1.014 Exponential Constant M+ p Xylene 524.2 0.127 0.033 3.846 Exponential Exponential Magnesium 1620 99.662 176.736 0.564 Exponential Constant Manganese 1620 6.531 4.363 1.497 Constant Constant Manganese 200.8 0.106 0.074 1.419 Constant Constant Mercury 200.8 0.062 0.014 4.550 Exponential Hybrid Methacrylonitrile 524.2 0.643 0.529 1.216 Exponential Hybrid Methyl Iodide 524.2 0.173 0.099 1.746 Exponential Exponential Methyl Tert butyl Ether 524.2 0.195 0.154 1.266 Exponential Exponential Methylacrylate 524.2 0.549 0.551 0.995 Exponential Exponential Methylene Chloride 502.2 ELCD 2.727  1.325  2.057 Constant Constant Methylene Chloride 524.2 0.276 0.159 1.737 Exponential Exponential Methylmethacrylate 524.2 0.484 0.366 1.322 Exponential Linear Molybdenum 1620 2.917 5.783 0.504 Exponential Constant Molybdenum 200.8 0.262 0.005 47.826 Constant Constant N butylbenzene 502.2 PID 0.139 0.049 2.819 Exponential Linear N butylbenzene 524.2 0.136 0.052 2.605 Exponential Exponential N propylbenzene 502.2 PID 0.089 0.100 0.889 Exponential Constant N propylbenzene 524.2 0.231 0.050 4.596 Exponential Hybrid Naphthalene 524.2 0.175 0.180 0.968 Exponential Exponential Nickel 1620 23.784 40.205 0.592 Exponential Constant Nickel 200.8 0.076 0.068 1.124 Exponential Constant Table 9. Comparison of 16 point and 5 point Single laboratory IDEs ( SL IDEs) for the Episode 6000 Dataset Analyte Method Procedure SL IDE ( 16) SL IDE ( 5) SL IDE( 16)/ SL IDE( 5) SL IDE 16 Model SL IDE 5 Model Draft Document for Peer Review  Do Not Circulate  August 2002 C 43 o xylene 524.2 0.161 0.084 1.925 Exponential Exponential o xylene+ styrene 502.2 PID 0.111 0.145 0.769 Exponential Constant P isoproptol+ 1,4 dcb 502.2 PID 0.153 0.143 1.068 Exponential Constant Pentachloroethane 524.2 0.337 0.419 0.805 Exponential Linear Sec butylbenzene 502.2 PID 0.079 0.053 1.504 Exponential Exponential Sec butylbenzene 524.2 0.132 0.038 3.422 Exponential Exponential Selenium 1620 1.915 1.757 1.090 Exponential Exponential Selenium 200.8 0.410 0.311 1.317 Exponential Exponential Silver 1620 10.219 11.118 0.919 Exponential Constant Silver 200.8 0.010  0.030  0.348 Exponential Exponential Sodium 1620 133.007 134.645 0.988 Exponential Exponential Styrene 524.2 0.119 0.045 2.676 Exponential Exponential Tert butylbenzene 502.2 PID 0.073 0.049 1.498 Exponential Exponential Tert butylbenzene 524.2 0.170 0.055 3.093 Exponential Exponential Tetrachloroethene 502.2 ELCD 0.051 0.045 1.119 Exponential Exponential Tetrachloroethene 502.2 PID 0.157 0.097 1.607 Exponential Linear Tetrachloroethene 524.2 0.379 0.526 0.721 Exponential Linear Thallium 1620 1.208 1.198 1.009 Exponential Linear Thallium 200.8 0.001 0.000 3.140 Exponential Exponential Thorium 200.8 0.003 0.000 7.428 Exponential Constant Tin 1620 1.200 4.383 0.274 Exponential Exponential Titanium 1620 5.238 19.982 0.262 Exponential Constant Toluene 502.2 PID 0.061 0.061 0.999 Exponential Constant Toluene 524.2 0.130 0.142 0.918 Exponential Constant 1 Total Phosphorus 365.2 0.013 0.011 1.219 Exponential Exponential Total Suspended Solids 160.2 2.877 2.131 1.350 Exponential Exponential Trans 1,2 dichloroethene 502.2 ELCD 0.065 0.061 1.069 Exponential Linear Trans 1,2 dichloroethene 524.2 0.255 0.072 3.531 Exponential Hybrid Trans 1,3 dichloropropene 502.2 ELCD 0.082 0.021 3.845 Exponential Exponential Trans 1,3 dichloropropene 502.2 PID 0.085 0.110 0.774 Exponential Exponential Trans 1,3 dichloropropene 524.2 0.204 0.127 1.613 Exponential Exponential Trans 1,4 dichloro 2 butene 524.2 1.182 1.205 0.981 Exponential Exponential Trichloroethene 502.2 ELCD 0.050 0.013 3.715 Exponential Exponential Trichloroethene 502.2 PID 0.096 0.080 1.189 Exponential Exponential Table 9. Comparison of 16 point and 5 point Single laboratory IDEs ( SL IDEs) for the Episode 6000 Dataset Analyte Method Procedure SL IDE ( 16) SL IDE ( 5) SL IDE( 16)/ SL IDE( 5) SL IDE 16 Model SL IDE 5 Model Draft Document for Peer Review  Do Not Circulate  August 2002 C 44 Trichloroethene 524.2 0.288 0.329 0.875 Exponential Linear Trichlorofluoromethane 502.2 ELCD 1.997 0.660 3.025 Constant Constant Trichlorofluoromethane 524.2 0.307 0.290 1.059 Exponential Exponential Uranium 200.8 0.001 0.000 4.743 Exponential Exponential Vanadium 1620 10.063 8.643 1.164 Exponential Exponential Vanadium 200.8 0.845 0.987 0.856 Exponential Linear Vinyl Chloride 502.2 ELCD 3.521 0.369 9.543 Constant Linear Vinyl Chloride 524.2 0.295 0.180 1.641 Exponential Linear WAD Cyanide 1677 0.672 1.243 0.541 Linear Constant Xylene ( Total) 524.2 0.111 0.030 3.735 Exponential Exponential Yttrium 1620 3.119 13.404 0.233 Exponential Constant Zinc 1620 4.415 6.661 0.663 Exponential Constant Zinc 200.8 1.497 5.061 0.296 Exponential Constant Note: ELCD or PID in the Procedure column indicates the photo ionization detector ( PID) or electrolytic conductivity detector ( ELCD) in EPA Method 502.2 1 Original model picked was Hybrid, but failed to converge Summary Statistics for Table 9 IDE( 16)/ IDE( 5) ( all analytes) IDE( 16)/ IDE( 5) ( same model used) IDE( 16)/ IDE( 5) ( different models used)

Number of Analytes 198 108 90 Minimum:  133.113  133.113 0.050 25th percentile: 0.876 1.072 0.564 Median: 1.270 1.419 0.919 75th percentile: 2.328 2.310 2.122 Maximum: 62.020 47.826 62.020 Number of analytes Percent of analytes p value ( for percent= 50)

SL IDE ( 16) > SL IDE ( 5) ( all analytes) 133 67.17% < 0.0001 SL IDE ( 16) > SL IDE ( 5) ( same model used) 91 84.26% < 00001 SL IDE ( 16) > SL IDE ( 5) ( different models used) 43 48.31% 0.832 Draft Document for Peer Review  Do Not Circulate  August 2002 C 45