Evaluation of methods for analysis of lead in air particulates: An intra-laboratory and interlaboratory

Transcription

1 Evaluation of methods for analysis of lead in air particulates: An intra-laboratory and interlaboratory comparison Frank X. Weber, James M. Harrington, Andrea McWilliams, Keith E. Levine Trace Inorganics Department, RTI International, Research Triangle Park, NC RTI International is a trade name of Research Triangle Institute.

2 Federal Reference Method Designated method for the analysis of specific analytes. - Law of the land, must be used unless equivalence can be show in great detail - Ensures that everyone is performing the same method - Suitable for intended purpose, thoroughly tested

3 Why do we need a new FRM? In 2008, guidelines were revised for allowable concentration of lead (Pb) in total suspended particulate matter (TSP) set forth in the National Ambient Air Quality Standards (NAAQS) Decreased limit of 1.5 µg/m 3 to 0.15 µg/m 3. Lower emission with the removal of lead from gasoline. Exposure studies have linked adverse health outcomes with advances in science.

4 Then and Now 1970 Dart 2014 Dart

5 Then and Now FRM ( ) Flame Atomic Absorption Spectroscopy (FAAS) Detection Limit challenged No one really using the technique RIP FRM ( present) Inductively Coupled Plasma Mass Spectrometry (ICP- MS) Sensitivity to spare Easily captures isotopic information Adaptable to any future level or element changes

6 Where to Start a New FRM? Existing Federal Equivalent Methods Already tested and proven against existing FRM 40 CFR Part Comparability shown Already in use by labs Minimize equipment purchases Staff already familiar with the technique

7 FRM Basis Methods EQL Heated (80 C) ultrasonic water bath 1.03 M HNO 3 /2.23 M HCl EQL Heated graphite block digestion (95 C) 3.5% (v/v) HNO 3

8 s Glass Fiber / Quartz PM10

9 TSP and PM 10 Samplers TSP Doghouse sampler - 8 X 10 inch filters - Glass or quartz fiber filter PM 10 - Teflon filters, 47mm most common

10 Intra-lab MDLs Per 40 CFR Part 136, Appendix B SRMs NIST 1547 Peach Leaves NIST 2709 San Joaquin Soil NIST 2583 Indoor Dust NIST 2582 Powdered Paint QC Strips 3 levels; 30, 100, and 200% of the NAAQS s Results by 1978 FRM for comparison

11 Intra-lab Results Heated Ultrasonic Hotblock Test Description Acceptance Criteria Glass Fiber Quartz PTFE Glass Fiber Quartz Method Detection Limit µg/m µg/m µg/m µg/m µg/m µg/m 3 SRM 1547 Recovery SRM 2709 Recovery SRM 2583 Recovery SRM 2582 Recovery % 100±4 101±6 104±5 92±7 106± % 98±1 95±1 93±1 98±3 104± % 103±8 91±5 108±11 103±4 92± % 101±0 93±1 96±3 94±4 95±2 RSD of replicate measurements RSD of 3 replicates 3 % CFR Part 136, Appendix B

12 Intra-lab Results Heated Ultrasonic Hotblock Test Description Acceptance Criteria Glass Fiber Quartz PTFE Glass Fiber Quartz Method Detection Limit µg/m µg/m µg/m µg/m µg/m µg/m 3 SRM 1547 Recovery SRM 2709 Recovery SRM 2583 Recovery SRM 2582 Recovery % 100±4 101±6 104±5 92±7 106± % 98±1 95±1 93±1 98±3 104± % 103±8 91±5 108±11 103±4 92± % 101±0 93±1 96±3 94±4 95±2 RSD of replicate measurements RSD of 3 replicates 3 % CFR Part 136, Appendix B

13 Intra-lab Results Heated Ultrasonic Hotblock Test Description Acceptance Criteria Glass Fiber Quartz PTFE Glass Fiber Quartz Method Detection Limit µg/m µg/m µg/m µg/m µg/m µg/m 3 SRM 1547 Recovery SRM 2709 Recovery SRM 2583 Recovery SRM 2582 Recovery % 100±4 101±6 104±5 92±7 106± % 98±1 95±1 93±1 98±3 104± % 103±8 91±5 108±11 103±4 92± % 101±0 93±1 96±3 94±4 95±2 RSD of replicate measurements RSD of 3 replicates 3 % CFR Part 136, Appendix B

14 Intra-lab Heated Ultrasonic Hotblock Test Description Acceptance Criteria Glass Fiber Quartz PTFE Glass Fiber Quartz Analytical Bias 2 7% ± Analytical Precision 2 10% Intra-Laboratory Method Precision 3 10% Intra-Laboratory Reproducibility 4 20% N/A CFR Part 58, Appendix A 3 40 CFR part Within laboratory method reproducibility for the four participating laboratories computed as %CV

15 Intra-lab Heated Ultrasonic Hotblock Test Description Acceptance Criteria Glass Fiber Quartz PTFE Glass Fiber Quartz Analytical Bias 2 7% ± Analytical Precision 2 10% Intra-Laboratory Method Precision 3 10% Intra-Laboratory Reproducibility 4 20% N/A CFR Part 58, Appendix A 3 40 CFR part Within laboratory method reproducibility for the four participating laboratories computed as %CV

16 Intra-lab Heated Ultrasonic Hotblock Test Description Acceptance Criteria Glass Fiber Quartz PTFE Glass Fiber Quartz Spiked Extract Stability Average % Difference a ±10% of the original concentration Sample Extract Stability Average % Difference a ±10% of the original concentration a Stability of extracts tested for > 6 months at room temperature; average % difference between original and final concentration

17 Intra-lab Conclusions MDL Detection limits below 5% of the NAAQS limit. SRM Recoveries were within 10% for a mix of botanical, geological, and industrial standard reference materials. Other Bias within 8% Precision within 2% Stability of extract within 10%

18 Inter-laboratory Four laboratories were needed Number of labs limited by sample size Equipment and supplies list prepared Volunteer labs selected Laboratories Identified Two government One commercial One not for profit Gave a good mix of instruments and backgrounds

19 Inter-laboratory Each lab received a total of 14 filter strips per media type. 7 strips for heated ultrasonic bath digestion 7 strips for heated graphite block digestion Each lab received 3 spiked filter strips per media type. High, medium, and low glass fiber filter High, medium, and low quartz fiber filter 30, 100, and 200% of NAAQS, respectively Each lab received an aliquot of the PM 10 extraction. PM 10 filters cannot be split Only a limited number available in the desired concentration range

20 Inter-laboratory Each laboratory received adjacent pairs of strips cut from the same filter. Used For FAAS Analysis A B C D E F G H

21 Inter-lablaboratory Example distribution Lab1 Lab2 Lab3 Lab4 Used For FAAS Analysis A B C D E F G H

22 Inter-lablaboratory Random distribution Lab1 Lab2 Lab3 Lab4 Used For FAAS Analysis A B C D E F G H Used For FAAS Analysis A B C D E F G H Used For FAAS Analysis A B C D E F G H

23 Inter-laboratory Spiked QC Strips PM10 Extract 200% 100% 20% Glass fiber Quartz

24 Inter-laboratory Considerations The analytical goals have to take into account variability of samples. Bias and precision goals have to be realistic Evaluate the results of decoupled analysis to assess analytical differences.

25 Inter-lab Heated Ultrasonic Hotblock Test Description Acceptance Criteria Glass Fiber Quartz PTFE Glass Fiber Quartz Inter-Laboratory Reproducibility 1 20% Decoupled Extraction Method Variability N/A N/A FEM Approval Precision, % difference 3 FEM Approval Comparability 15% < 2.3 % N/A N/A < 6.6 % N/A ±20% % N/A N/A % N/A 1 Between-laboratory method reproducibility across the four participating laboratories. 2 Goal was to assess the variability due to the extraction methods; therefore no acceptance criterion was specified. 3 Insufficient PTFE filter extract was available to perform this test.

26 Method Comparison

27 Comparability for Heated Ultrasonic ID C1-R1 C1-R2 C1-R3 C2-R1 C2-R2 C2-R3 C3-R1 C3-R2 C3-R3 D MOPB % 2.7% 5.7% 6.1% 3.1% 6.1% 7.0% 4.1% 7.1% D MOPB % -10.9% 3.7% -5.0% -10.6% 4.0% -5.8% -11.3% 3.2% D MOPB % 4.2% 8.8% 6.6% 5.0% 9.6% 7.0% 5.3% 9.9% D MOPB % 7.9% 11.9% 5.9% 9.3% 13.3% 4.0% 7.4% 11.4% D MOPB % 2.4% 5.5% -1.5% 1.1% 4.2% -0.4% 2.3% 5.4% D MOPB % -13.1% -1.5% -4.7% -11.6% 0.2% -5.0% -11.9% -0.1% D MOPB % 0.3% 0.2% -2.0% 0.7% 0.6% -1.5% 1.1% 1.0% D MOPB % -0.7% 5.1% 3.9% 1.0% 6.9% 3.5% 0.6% 6.5% Comparability Test of FEM EQL (Heated Ultrasonic) against FAAS* * Requirement is 20% comparability; C = FEM EQL as a candidate FRM; R = FAAS reference method

28 Comparability for Block Digestion ID C1-R1 C1-R2 C1-R3 C2-R1 C2-R2 C2-R3 C3-R1 C3-R2 C3-R3 D MOPB % -6.0% -3.2% -2.2% -4.9% -2.1% -3.4% -6.1% -3.4% D MOPB % 2.5% 12.4% 4.3% 0.75% 1.5% 6.2% 2.6% 12.5% D MOPB % -0.23% 3.5% -0.21% 3.0% 6.8% -2.4% 0.73% 4.5% D MOPB % 0.48% 3.6% 3.7% 6.4% 9.7% -2.8% -0.29% 2.8% D MOPB % -2.0% 5.9% 0.81% -3.3% 4.5% 4.2% -0.06% -2.7% * Requirement is 20% comparability; C = FEM EQL as a candidate FRM; R = FAAS reference method

29 Inter-lab Conclusions Results Bias values ranged from 3.78 to 6.89%, demonstrating good agreement of the results between the laboratories of this study. Precision was less than the target 10% CV, demonstrating highly reproducible results within a testing facility over a broad range of concentrations. Decoupled analysis mean %CV of measured Pb in samples ranged from 3.38 to 7.80%, variation in recovered Pb concentrations was likely due to differences in sample collection technique.

30 Data Conclusions Comparison to 1978 FRM For all sample filters, the comparability values fall within the acceptance goal of ±20% comparability, demonstrating equivalency of the results obtained by the two methods. Comparability takes into consideration the variability of the sampler.

31 Conclusion Method Conclusion Both extraction methods in the 2013 FRM have demonstrated accuracy, precision, sensitivity, and comparability (to each other and FAAS) by multiple laboratories. ICP-MS will be able to accommodate any future lowering of the NAAQS limit. Both methods utilize economical extraction equipment that offer high throughput.

32 Alternative Analysis Energy Dispersive X-Ray Fluorescence (EDXRF) - Non-destructive test - No sample preparation required - Typical analysis is for 33 elements - Automated analysis

33 Handling Modules retrieved from sampling site. s extracted from module. s weighed. Off to the lab for analysis.

34 Instrument Detection Limits µg/filter Pb Mn Ni Zn ICP-MS XRF

35 Pb Comparison n=624, r=0.995 ICP-MS vs. XRF Pb µg/filter XRF ICP-MS vs. XRF Linear (ICP-MS vs. XRF) ICP-MS

36 Pb at NAAQS Levels n=526, r=0.927 ICP-MS vs. XRF Pb in µg/filter 30% to 200% of NAAQS Limit XRF ICP-MS vs. XRF Linear (ICP-MS vs. XRF) ICP-MS

37 Mn Comparison n=848, r=0.945 XRF vs. ICP-MS 0.05 to 1.5 µg/filter XRF XRF vs ICP-MS 0.05 to 1.5 Linear (XRF vs ICP-MS 0.05 to 1.5) ICP-MS

38 Ni Comparison n=577, r=0.964 XRF vs. ICP-MS Ni µg/filter XRF XRF vs. ICP-MS Ni Linear (XRF vs. ICP-MS Ni) ICP-MS

39 Zn Comparison n=798, r=0.910 XRF vs. ICP-MS Zn µg/filter XRF XRF vs. ICP-MS Zn Linear (XRF vs. ICP-MS Zn) ICP-MS

40 Potential Sources of Differences /Module handling. - Different technicians at different sites. - Gloves can contaminate (Zn, Ca). Uniformity of particle deposition. - XRF does not measure the entire exposed filter area. - ~10 X 12mm ellipse

41 Potential Sources of Differences Sample handling in the laboratory - Any contamination on support ring or back of the filter will be included in ICP-MS measurement. Calibration Method - XRF typically has 2-3 points on curve, ICP-MS typically has 5-7 points over a focused range.

42 More Information Frank X. Weber, James M. Harrington, Andrea McWilliams, Keith E. Levine Trace Inorganics Department, RTI International, Research Triangle Park, NC Publication: Environmental Science: Processes & Impacts, 2014,16, Frank X. Weber Laboratory Manager