Results of the Validation Study for Determination of. Trace Metals at EPA Water Quality Criteria Levels

Transcription

1 Results of the Validation Study for Determination of Trace Metals at EPA Water Quality Criteria Levels U.S. EPA Office of Water Office of Science and Technology Engineering and Analysis Division Washington, DC 20460

2 Results of the Validation Study for the Determination of Trace Metals at EPA WQC Levels 2 Draft, April 1995

3 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels Acknowledgments This report was prepared under the direction of William A. Telliard of the Engineering and Analysis Division within the EPA Office of Water. This document was prepared by DynCorp EENSP under EPA Contract No. 68-C Other contributors to this study included Interface, Inc., Battelle Marine Sciences Laboratory (Sequim, WA), Battelle Ocean Sciences (Duxbury, MA), Research Triangle Institute, Skidaway Institute of Oceanography, and Texas A&M University's Trace Element Research Laboratory. Disclaimer This report has been reviewed by the Engineering and Analysis Division, U.S. Environmental Protection Agency, and approved for publication. Mention of company names, trade names, or commercial products does not constitute endorsement or recommendation for use. Questions or comments regarding this report should be addressed to: W.A. Telliard USEPA Office of Water Analytical Methods Staff Mail Code M Street, SW Washington, D.C / Requests for additional copies should be directed to: USEPA NCEPI Kenwood Road Cincinnati, OH /

4 TABLE OF CONTENTS SECTION 1 INTRODUCTION... 1 SECTION 2 STUDY DESIGN PHASE 1 STUDY DESIGN Objectives... 3 Table 2-1: Metals to be Tested in Each EPA Method Methodology/Approach PHASE 2 STUDY DESIGN Objectives Methodology/Approach LABORATORIES... 6 SECTION 3 RESULTS Data Reporting, Verification and Validation Phase 1: MDL Results... 9 Table 3-1: Method Detection Limit (MDL) Results from QC Supplement Validation Study Phase 2: Verification of QC Acceptance Criteria Table 3-2: Verification of QC Acceptance Criteria for Method (1638) Table 3-3: Verification of QC Acceptance Criteria for Method (1639) Table 3-4: Verification of QC Acceptance Criteria for Method (1640) Table 3-5: Verification of QC Acceptance Criteria for Method (1637) Table 3-6: Verification of QC Acceptance Criteria for Method (1636) SECTION 4 DISCUSSION Selection of MDLs for EAD Methods QC Acceptance Criteria Mercury, Arsenic, and Trivalent Chromium (Cr 3+ ) SECTION 5 CONCLUSIONS APPENDIX A 40 CFR Part 136, Appendix B Draft, April 1995

5 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels SECTION 1 INTRODUCTION The Clean Water Act (CWA) requires that ambient water quality criteria (WQC) published by EPA reflect the latest scientific knowledge concerning the physical fate (e.g., concentration and dispersal) of pollutants, the effect of pollutants on ecological and human health and welfare, and the effect of pollutants on biological community diversity, productivity, and stability. Although CWA does not require EPA to consider analytical capability when setting WQC levels, the identification of methods capable of measuring pollutants at WQC levels is an obvious goal. In 1992, EPA promulgated WQC for 14 States at 40 CFR Part 131. (1) This regulation, known as the National Toxics Rule, included numeric criteria for 13 metals. The criteria for some of these metals require measurement capabilities at levels as much as 280 times lower than those achievable using existing EPA methods and required to support technology-based regulations. In order to implement the use of these metals criteria in CWA permits and programs, the Engineering and Analysis Division (EAD), within EPA's Office of Water, was tasked with developing methods for measurement of metals at the lowest WQC levels specified in the National Toxics Rule. In developing such methods, EAD first sought to utilize existing instrumentation and technology to the maximum extent possible. EAD also sought to ensure that the methods would provide the quality control requirements necessary to demonstrate the reliability of data gathered at the low concentrations associated with water quality criteria. Finally, EAD sought to minimize method development costs by basing its approaches on techniques already in use by marine chemists familiar with measuring metals at ambient levels. As a first step towards achieving these objectives, EAD convened a workgroup of recognized trace metal experts from the academic research community, commercial laboratories, Environment Canada, and EPA. The workgroup initially met in November 1993 with the principal objective of identifying the least expensive sampling and analysis techniques that would be likely to yield reliable measurements at WQC levels. During this meeting, several EPA 200-series methods were identified as starting points for the analysis of most of the metals listed in the National Toxics Rule. Meeting participants also identified additional sample handling and quality control techniques that would be necessary to ensure reliable measurements at these levels. Following the November 1993 meeting, EAD drafted a Quality Control Supplement for Determination of Metals at Ambient Water Quality Criteria Levels (the "QC Supplement"). The QC Supplement added rigorous quality control to the procedures found in six EPA 200-series methods. It consisted primarily of (1) additional sampling handling procedures designed to preclude contamination at WQC levels, and (2) additional QC elements designed to define the quality of results at WQC levels and to harmonize the QC elements in the EPA 200-series methods with those found in EPA's and 600- series wastewater methods. Preliminary QC acceptance criteria for each of the QC elements were developed from performance data given at the end of each 200-series method; these preliminary acceptance criteria were given in Table 2 of the QC Supplement. In August 1994, EAD initiated several single laboratory studies designed to validate the procedures and 1 "Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollutants; States' Compliance" (also referred to as "The National Toxics Rule"), 40 CFR Part 131, (57 FR 60848, December 22, 1992). Draft, April

6 Results of the Validation Study for the Determination of Trace Metals at EPA WQC Levels QC acceptance criteria detailed in the QC Supplement. Although the QC Supplement was initially drafted to supplement six EPA 200-series methods, EAD chose to validate only five of these methods because (1) it was believed that these five methods would yield detection limits necessary to provide reliable measurements at WQC levels and (2) the methods employed technologies that were both widely available and cost-effective for single element and for multi-element determinations. (2) The methods validated and the technologies that they employ are as follows: Method 200.8: Inductively coupled plasma/mass spectrometry (ICP/MS) Method 200.9: Stabilized temperature graphite furnace atomic absorption spectrophotometry (STGFAA) Method : Chelation preconcentration and ICP/MS Method : Chelation preconcentration and STGFAA Method 218.6: Hexavalent chromium by ion chromatography EAD's intent in conducting these validation studies was to verify that the procedures outlined in the supplemented methods were capable of yielding reliable data at WQC levels, and to use the study results to develop 1600-series methods that integrate the procedures in the QC Supplement with those contained in the 200-series methods. This report gives the results of EAD's validation studies. 2 The two methods that cover the most metals (Methods and 200.9) had been promulgated for use in EPA's drinking water programs at 40 CFR (k)(1) on December 5, 1994 (59 FR 62456). These methods, and Method 218.6, are also scheduled for proposed use in EPA's wastewater program at 40 CFR Part 136 in late Draft, April 1995

7 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels SECTION 2 STUDY DESIGN In order to minimize costs, the studies described in this report were designed as single laboratory studies aimed at providing EAD with some level of verification that the procedures and QC acceptance criteria specified in the draft QC Supplement could be met by environmental laboratories. To further minimize costs, each single laboratory study was conducted in two phases. In the first phase, each laboratory was to attempt to achieve the target method detection limit (MDL; 40 CFR 136, Appendix B) or to come as close as possible to the target MDL. Target MDLs were set at one-tenth the lowest water quality criterion for each metal. In the second phase, each laboratory was to validate the preliminary QC acceptance criteria given in Table 2 of the QC Supplement. Performance of the second phase was contingent upon successful completion of the first phase. Details of the two-phase design are given in Sections 2.1 and 2.2 of this report. To the extent that costs and schedules would allow, the single laboratory validations of each supplemented method were performed concurrently by more than one laboratory. More extensive interlaboratory method validation studies may be performed at some later date, if warranted. The original study design is fully described in a study plan dated June (3) This study plan was supplemented with a statement of work (SOW) to describe specific technical requirements to be followed by each contract laboratory performing these studies. (4) The final study design is summarized below PHASE 1 STUDY DESIGN The first phase of the study focused on the use of spiked reagent water to demonstrate the ability of supplemented EPA methods to yield MDLs less than or as close as possible to one-tenth the lowest WQC levels published in the National Toxics Rule (target MDLs). Where appropriate, the WQC levels listed in the National Toxics Rule were adjusted for dissolved levels and a hardness of 25 mg/l CaCO 3. The technical approach for Phase 1 is as follows Objectives The objectives of Phase 1 were to: (1) Confirm that the QC Supplement could be combined with EPA Methods 200.8, 200.9, , , and to provide the sample handling and quality control procedures necessary to achieve the target MDLs for the metals listed in Table 2-1; (2) Attempt to achieve, or approach as closely as possible, the target MDL in a minimum of one and as many as three experienced and available laboratories; 3 Study Plan for Validating the Quality Control Supplement for Determination of Metals at Ambient Water Quality Criteria Levels, June Copies of this study plan are available from the Sample Control Center (operated by DynCorp EENSP), 300 N. Lee Street, Alexandria, VA 22314, (703) Statements of Work for "Validation of the Quality Control Supplement for Determination of Metals at Ambient Water Quality Criteria Levels" and "Validation of the Quality Control Supplement for Determination of Metals at Ambient Water Quality Criteria Levels and Determination of Chromium VI by EPA Method 218.6," DynCorp EENSP (formerly Dyncorp Viar Inc.). Draft, April

8 Results of the Validation Study for the Determination of Trace Metals at EPA WQC Levels (3) Identify method/analyte combinations that should be the target of further study in Phase 2; and (4) Identify further method development needs. Table 2-1: Metals to be Tested in Each EPA Method Method Number Metal(s) antimony, arsenic, cadmium, copper, lead, nickel, silver, thallium, zinc antimony, cadmium, nickel, selenium, zinc cadmium, copper, lead, nickel cadmium, lead hexavalent chromium As can be seen from Table 2-1, MDL studies were conducted for some metals by more than one method. This approach was taken wherever schedule and resource constraints permitted in order to maximize the number of methods that could be demonstrated to provide the required detection levels. Maximizing the number of methods can provide increased flexibility for permit writers, permittees, or other groups seeking to determine metals concentrations at ambient criteria levels Methodology/Approach Each laboratory was instructed to perform the MDL determination in accordance with the procedures given in 40 CFR 136, Appendix B - Definition and Procedure for the Determination of the Method Detection Limit - Revision This procedure, which is provided in Appendix A of this report, involves the analysis of at least seven replicate samples that are spiked to contain the target analyte(s) at a concentration of one to five times the estimated MDL. Laboratories performing these studies were required to notify EPA's Sample Control Center (SCC) of their estimated MDLs and spike levels prior to commencing these studies. (5) Following SCC concurrence with these spike levels, each laboratory prepared a spike solution containing the target compound(s) at the designated concentrations. This solution was then spiked into a reagent water sample to produce seven spiked replicate aliquots. In order to verify that the spike level chosen was appropriate, laboratories were instructed to perform the two-aliquot test described in step 4b of the MDL procedure and report the results of that test to SCC. If the first two measurements indicated that the sample concentration was not in the correct range, the laboratory was required to repeat step 4b (analysis of two spiked aliquots) until the desired spike level was achieved. If the results of this test indicated that the spike levels chosen were in the desirable range for determination of the MDL, laboratories were instructed to proceed with analysis of the five remaining aliquots. All seven measurements were then used for calculation of the MDL. 5 The Sample Control Center (SCC) is operated by DynCorp EENSP under EPA Contract Draft, April 1995

9 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels PHASE 2 STUDY DESIGN The second phase of the study focused on validating the QC acceptance criteria contained in the draft QC Supplement. This phase was pursued for only those method/metal combinations that yielded MDLs less than or close to the MDLs targeted in Phase 1. Specific objectives for this phase are summarized below and are followed by a brief summary of the design for this phase Objectives The primary objectives of Phase 2 were to: (1) Determine if the QC acceptance criteria specified in Table 2 of the QC Supplement were reasonable for the metal and method combinations to be evaluated in this phase of the study. The Table 2 QC specifications included acceptance criteria for initial precision and recovery (IPR) analyses, calibration verification (VER), ongoing precision and recovery (OPR) analyses, and matrix spike (MS) and matrix spike duplicate (MSD) analyses. (2) Determine the minimum level (ML) of quantification for each of the metal/method combinations to be evaluated in this phase of the study. (3) Establish the lowest calibration point at a rounded value equal to or slightly less than the ML derived from the Phase 1 MDL data. (4) Identify further method development needs. (5) Identify and make further revisions needed to the QC Supplement. (6) Develop technical details and language for new 1600-series methods that integrate the 200-series methods with the revised QC Supplement Methodology/Approach The Phase 2 study design was centered around the use of the QC Supplement and the referenced 200- series methods to analyze four spiked reagent water replicates and two spiked aqueous field sample replicates. The results of the reagent water analyses were used to assess the precision and accuracy that could be achieved using the QC Supplement and the referenced methods. The results of the spiked field sample replicates were used to assess the precision and accuracy of the method in a real world matrix. Laboratories were instructed to follow all QC requirements and analytical procedures stated in the QC Supplement and the referenced methods. The results of these associated QC analyses (e.g., blanks, calibration verification, etc.) were used to further assess the validity of the method and the performance of the laboratories. For the purpose of this study, an interim ML was calculated by multiplying the MDL determined in Phase 1 by This 3.18 value is the ratio between the Student's t multiplier used to determine the MDL (3.143) and the 10 times multiplier used by the American Chemical Society (ACS) to establish the limit of quantitation (LOQ). For example, if the MDL found is 7.6, the interim ML would be equal to 7.6 times 3.18, which equals To simplify calibration, the interim ML was rounded to the number nearest to (1, 2, or 5) x 10 n, where n is an integer. In the example above, the interim ML (24.4) would be rounded to Draft, April

10 Results of the Validation Study for the Determination of Trace Metals at EPA WQC Levels 20. In cases where more than one laboratory conducted a Phase 1 MDL study for the same metal/method combination, the highest MDL was generally chosen for calculation of an ML that would be used by all laboratories in Phase 2. In accordance with Section 10.1 of the QC Supplement, the laboratories were instructed to initially calibrate each instrument with a minimum of three calibration points. One of these points was to be near the upper end of the linear range, and another was to be at or slightly below the ML. Each laboratory was also instructed to create IPR and OPR solutions containing the metal of interest at two times the rounded ML. This level was consistent with those specified in Sections 9.2 and 9.6 of the QC Supplement. Field samples used for the performance of MS/MSD analyses were collected from sources known to contain the metal(s) of interest at ambient concentrations at or below the levels of interest in this study. To ensure that the samples used for the performance of MS/MSD analyses were not contaminated during sample collection and transport, the samples were collected by marine research laboratory personnel who are highly experienced in the collection and analysis of samples at ambient WQC levels. After determining the background concentration, the laboratories prepared matrix spike and matrix spike duplicate samples at a concentration of 1-5 times the rounded ML or 1-5 times the background concentration, whichever was higher. Generally, the IPR, OPR, and MS/MSD analyses were performed in accordance with the procedures described in the QC Supplement, the applicable EPA analytical method, and the SOW. In a few cases, a laboratory either spiked the IPR or OPR at a level higher than 2 times the rounded ML or did not calibrate at the ML. In these instances, the other laboratories participating in the study performed the analyses correctly and were able to meet all QC acceptance criteria. Difficulties encountered during the course of analysis were conveyed to SCC and, if appropriate, instructions were given to modify the procedures written in the supplemented EPA method, and document any changes. As warranted by the analytical data, all such changes were used to revise the methods that resulted from this study LABORATORIES Four laboratories performed the Phase 1 and Phase 2 studies. These laboratories were Battelle Ocean Sciences (Battelle), Skidaway Institute of Oceanography (Skidaway), Texas A&M University's College of Geosciences (Texas A&M), and Research Triangle Institute (RTI). Within Battelle, some tests were performed at the laboratory in Duxbury, Massachusetts, and others at the laboratory at Sequim, Washington. The four laboratories were chosen because of their expertise, their experience in the determination of trace metals, their availability, and the prices bid to perform the analyses required in the study plan and SOW. Based on discussions with the laboratories at the inception of the study it was recognized that, because some laboratories did not have all of the equipment necessary and some laboratories had old equipment, all laboratories would not be able to achieve all target MDLs for all analytes in all methods. Therefore, if the laboratory stated that it believed that it could achieve the MDL for a given metal in a given method, or was willing to make a good-faith attempt, that laboratory was contracted to proceed. Also, any laboratory was free to decline attempting to achieve the MDL for any given metal and was free to decline testing with any given method. Although use of alternative methods was prohibited, laboratories were authorized to utilize the flexibility given in Section of the QC Supplement. For example, instead of using the Dionex column specified in Methods and , Skidaway used 8-hydroxyquinoline immobilized 6 Draft, April 1995

11 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels on silica gel, and Battelle used a APDC/cobalt precipitation technique for preconcentration. Similarly, Texas A&M replaced the off-line preconcentration technique specified in Method with a reductive precipitation technique developed by the National Research Council of Canada. In all cases, laboratories were required to inform SCC of any proposed changes to the methods (including those within the scope of flexibility allowed by Section 9.1.2) and document those changes in writing. Based on these conditions, a total of two laboratories (Battelle and Skidaway) attempted to validate the supplemented procedures in Methods and , and three laboratories (Battelle, Skidaway, and Texas A&M) attempted to validate the supplemented procedures in Methods and Validation of Method was performed in accordance with a separate study; therefore only one laboratory (RTI) validated the supplemented procedures in this method. If a given laboratory was unable to achieve or approach the MDL in Phase 1, that laboratory was not authorized to proceed with Phase 2. This occurred in only two instances. Due to uncontrollable contamination problems, Texas A&M did not perform the zinc analyses for Method In addition, due to a high MDL, Texas A&M did not continue with Phase 2 for lead analyses by Method Draft, April

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13 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels SECTION 3 RESULTS Data Reporting, Verification and Validation Laboratories were instructed to report results in accordance with requirements in the SOW. These requirements included submission of: C C C C C A written report detailing problems with, or deviations from, the referenced methods; problems associated with the analysis of specific samples; and comments on the performance of the method on each metal studied. A list of samples analyzed and a run chronology. Summary reports of all analytical results in a format specified by SCC. Copies of all raw data, including quantitation reports, strip charts, spectra, bench sheets and laboratory notebooks showing tare and sample weights, sample volumes, solvent volumes and other data allowing the final results reported to be traced back to the analytical steps performed. MDL values reported to three significant figures. Data received were checked against the requirements in the SOW and study plan. Completeness of the data submissions was verified by ensuring that all required data were present, including results of all required tests, sample lists, run chronologies, summaries of analytical results, raw data, and copies of laboratory notebooks. Validation of data was performed by comparing each required data element to the requirements of the SOW. This included verification that (1) reagent water and ambient water samples were utilized as appropriate, (2) proper spike levels were used in the MDL studies and QC analyses, (3) the instruments were properly calibrated and that other method procedures were followed, and (4) the MDL was calculated per the MDL procedure. In those instances in which the requirements in the SOW were not met, an explanation was provided in the narrative report or was resolved through subsequent discussions with the laboratory Phase 1: MDL Results The MDLs and other data produced in these validation studies were ultimately used by EAD to prepare draft 1600-series methods that integrated the procedures given in the QC Supplement with those in the referenced 200-series methods on which the 1600-series methods were based. These draft 1600-series methods were released in April Table 3-1 lists the target MDL and the MDLs obtained from each laboratory in Phase 1, as well as the MDL actually used in the versions of the 1600-series methods resulting from this study. Each 1600-series method is denoted in parentheses next to the 200-series method on which it is based. As can be seen from Table 3-1, the MDLs in the EAD methods reflect the results obtained in this study, with two exceptions. The selenium MDL in Method 1638 was erroneously listed as 1.2 Fg/L; the MDL should be 0.45 Fg/L. The cadmium MDL in Method 1637 was incorrectly listed as µg/l; the correct MDL is µg/l. Draft, April

14 Table 3-1: Method Detection Limit (MDL) Results from QC Supplement Validation Study units = µg/l Sb Cd Cr 6+ Cu Pb Ni Se Ag Tl Zn Target MDL (1) Method (1638) Battelle Skidaway MDL (2) Method (1639) Battelle Skidaway Texas A&M MDL Method (1640) Battelle Skidaway MDL Method (1637) Battelle Skidaway Texas A&M MDL (2) Method (1636) RTI MDL Target MDL is 1/10 WQC level. 2 The MDLs listed for Se in Method 1638 (April 1995) and Cd in Method 1637 (April 1995) are incorrect. The MDLs provided in this table are correct. 10

15 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels Table 3-1 also shows that, with one exception, at least one laboratory met the target MDL for each metal in each method. The only exception was for lead by supplemented Method 200.8; in this instance, however, both laboratories came very close to the target. For nearly all analyses, blanks were low enough to not impact significantly the MDL. However, in a few instances, the blank levels were sufficiently high that blank subtraction was performed. The MDL results for each method are summarized in the list below. In this list, the supplemented 200- series method number is followed in parentheses with the number of the integrated 1600-series method. Method No. MDL Results (1638): With the exception of lead as described above, both laboratories were able to achieve the target MDLs for all metals listed in Table (1639): One laboratory met the target MDLs for all five metals; two laboratories met the target MDLs for four of the five metals; and all three laboratories met the target MDLs for three of the five metals (1640): Both laboratories easily met the target MDLs for all four metals (1637): The target MDL for cadmium was met easily by all three laboratories, but only Skidaway met the target MDL for lead (1636): The target MDL of 1.05 Fg/L for Cr 6+ was met easily by RTI Phase 2: Verification of QC Acceptance Criteria Details of the acceptance criteria verifications are summarized in Tables 3-2 through 3-6 for the five methods. These tables list the target QC acceptance criteria and results for each metal in each method for the IPR, VER, OPR, and MS/MSD tests. In nearly all instances, the laboratories met the QC acceptance criteria for each metal/method combination listed in Table 2-1. Draft, April

16 Table 3-2: Verification of QC Acceptance Criteria for Method (1638) all specifications expressed as percent Initial Precision and Recovery (Section 9.2) Metal s X Calibration Verification (Section 10.2) Ongoing Precision and Recovery (Section 9.6) Spike Recovery (Section 9.3) Antimony Target Skidaway /103 (RPD = 5.3) Battelle /111 (RPD = 4.1) Cadmium Target Skidaway /100.5 (RPD = 5.4) Battelle /104 (RPD = 1.2) Copper Target Skidaway /113 (RPD = 0.4) Battelle /102 (RPD = 4.5) Lead Target Skidaway /89 (RPD = 8.6) Battelle /92.3 (RPD = 1.9) Nickel Target Skidaway /90.8 (RPD = 17.3) Battelle /114 (RPD = 2.4) Selenium Target Skidaway /132 (RPD = 1.8) Battelle /124 (RPD = 6.1) Silver Target Skidaway /78 (RPD = 1.1) Battelle /85.9 (RPD = 4.4) Thallium Target Skidaway /92.5 (RPD = 4.5) Battelle /93 (RPD = 0) Zinc Target Skidaway /99.5 (RPD = 5.8) 12

17 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels Battelle /115 (RPD = 0.2) Draft, April

18 Table 3-3: Verification of QC Acceptance Criteria for Method (1639) all specifications expressed as percent Initial Precision and Recovery (Section 9.2) Calibration Verification (Section 10.2) Ongoing Precision and Recovery (Section 9.6) Spike Recovery (Section 9.3) Metal s X Antimony Target Skidaway /93 (RPD = 5.0) Battelle /110.1 (RPD = 1.2) Texas A&M /109.1 (RPD = 12.1) Cadmium Target Skidaway /92 (RPD = 3.3) Battelle /102.4 (RPD = 0.4) Texas A&M /88.4 (RPD = 0.2) Nickel Target Skidaway /85 (RPD = 20.7) Battelle /101 (RPD = 2.1) Texas A&M /107.4 (RPD = 9.3) Selenium Target Skidaway /103 (RPD = 13.8) Battelle /79 (RPD = 3.4) Texas A&M /100 (RPD = 6.1) 14

19 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels Zinc Target Skidaway /95 (RPD = 6.7) Battelle /102 (RPD = 1.2) Draft, April

20 Table 3-4: Verification of QC Acceptance Criteria for Method (1640) all specifications expressed as percent Initial Precision and Recovery (Section 9.2) Calibration Verification (Section 10.2) Ongoing Precision and Recovery (Section 9.6) Spike Recovery (Section 9.3) Metal s X Cadmium Target Skidaway /77.5 (RPD = 12.3) Battelle /97 (RPD = 11.7) Copper Target Skidaway /147 (RPD = 7.7) Battelle /150 (RPD = 12) Nickel Target Skidaway /81.8 (RPD = 1.3) Battelle /87.5 (RPD = 4.3) Lead Target Skidaway /45.4 (RPD = 14) Battelle /93.4 (RPD = 3.7) 16

21 Table 3-5: Verification of QC Acceptance Criteria for Method (1637) all specifications expressed as percent Initial Precision and Recovery (Section 9.2) Calibration Verification (Section 10.2) Ongoing Precision and Recovery (Section 9.6) Spike Recovery (Section 9.3) Metal s X Cadmium Target Skidaway /87.5 (RPD = 15.4) Battelle /95 (RPD = 2.5) Texas A&M /87.7 (RPD = 5.2) Lead Target Skidaway /36 (RPD = 20.3) Battelle /94.5 (RPD = 2.1) 17

22 Table 3-6: Verification of QC Acceptance Criteria for Method (1636) all specifications expressed as percent Initial Precision and Recovery (Section 9.2) Calibration Verification (Section 10.2) Ongoing Precision and Recovery (Section 9.6) Spike Recovery (Section 9.3) Metal s X Hexavalent Chromium Target RTI /107 (RPD = 4) 18

23 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels SECTION 4 DISCUSSION The validation studies described in this report demonstrated that the procedures given in the 200-series methods and the QC Supplement could yield reliable results at the lowest WQC specified in the National Toxics Rule. Based on these findings, EAD chose to proceed with development of five new 1600-series methods that integrated the procedures in the QC Supplement with those in the 200-series methods that were the subject of this study. In developing the 1600-series methods, EAD also integrated comments received from study participants and from Regions, States, and others who had reviewed the methods Selection of MDLs for EAD Methods In nearly all instances, laboratories were able to achieve the MDLs targeted in Phase 1 of the study. In developing MDLs for use in Phase 2 of the study, and for subsequent publication of MDLs and MLs in the 1600-series methods, EAD chose to utilize the highest MDL obtained for a given metal with a given method. This decision was made to ensure that more than one laboratory would be available for measurement of metals at ambient criteria levels. The only exception to this rule was for Texas A&M's MDL for lead in Method (EAD 1637). In this instance, the ML derived from the MDL would have been above the ambient criterion, so the MDL was not used, and Texas A&M was instructed to not perform Phase 2 for Method Instead, Battelle's MDL, which was the next highest, was used. In a few instances, the MDL determined for a given metal by a given laboratory was less than five times the spike level used the in MDL procedure. In these instances, the MDL was always well below the target value. The laboratory was not required to repeat the MDL test at a lower spike level because lowering the spike level would have resulted in an even lower MDL and the target had already been met QC Acceptance Criteria In nearly all instances, the laboratories verified the QC acceptance criteria specified in the QC Supplement for each metal/method combination tested. As was noted above in Section 3.3, at least one laboratory was able to achieve results that met the QC acceptance criteria in nearly all cases. In establishing QC acceptance criteria for each of the new methods, EAD utilized the acceptance criteria specified in the QC Supplement when these criteria were met by each of the participating laboratories. For instances in which one or more laboratories were unable to met the target acceptance criteria, each situation was examined on a case-by-case basis to determine if adjustment of the acceptance criteria was warranted. Acceptance criteria were not changed if (1) problems were related to a laboratory's instrument rather than the method, (2) problems were related to a specific matrix interference, or (3) the result from one or more laboratories met the criterion and the result from the laboratory that failed the criterion was associated with other data that indicated acceptable method performance. The acceptance criteria were adjusted if the data from one or more laboratories suggested difficulties with method performance. The final acceptance criteria can be found in Table 2 of each 1600-series method Mercury, Arsenic, and Trivalent Chromium (Cr 3+ ) It was recognized at the outset of this study that mercury, arsenic, and trivalent chromium were special Draft, April

24 Results of the Validation Study for the Determination of Trace Metals at EPA WQC Levels cases requiring analytical technologies beyond the scope of the methods employed in this study. Although arsenic was considered in the study plan, the laboratories involved in this study declined to attempt to measure this analyte using the techniques cited. As a result, mercury, arsenic, and trivalent chromium were not determined in this study. Development of methods for the determination of mercury and arsenic were performed separately and resulted in draft Methods 1631 and 1632, respectively. Procedures for the preparation of field samples for Cr 3+ determinations were included in Method 1669: Sampling Ambient Water for Trace Metals at EPA Water Quality Criteria Levels and analytical procedures were included in Method Draft, April 1995

25 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels SECTION 5 CONCLUSIONS The analytical technologies employed in this study were ICP/MS and STGFAA, with and without chelation and preconcentration, for 10 metals and ion chromatography for hexavalent chromium. The results obtained in Phase 1 of the study demonstrate that at least one laboratory can achieve the MDLs published for each metal in the new 1600-series methods. The results also show that the target MDLs can be achieved by ICP/MS, without chelation and concentration, for eight of the nine metals to which ICP/MS and STGFAA are applicable. Study results also suggest that lead is also amenable to ICP/MS analysis at these levels, but chelation and concentration may be required. These findings are encouraging, in that a single analytical technology (ICP/MS) can be used to determine nine of 13 metals in the National Toxics Rule. Because ICP/MS instruments have become widespread over the past decade, the ability to determine metals at ambient criteria levels will be dependent primarily on the cleanliness of sampling techniques and laboratories, rather than on the availability and capability of analytical hardware. The results of the tests in Phase 2 demonstrate that the adjusted QC acceptance criteria in the 1600 series analytical methods are reasonable, and that it should be possible for laboratories performing trace metals determinations to meet these criteria on a routine basis. Draft, April

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27 Results of the Validation Study for Determination of Trace Metals at EPA WQC Levels APPENDIX A 40 CFR Part 136, Appendix B - Definition and Procedure for the Determination of the Method Detection Limit - Revision 1.11 (reproduced from the Federal Register, Vol. 49, No. 209, Friday, October 26, 1984) Draft, April