PAH Analytical Techniques and Impacts on Risk Assessment

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This presentation summarizes the benefits of using isotope dilution high resolution mass spectrometry for detection of PAHs, especially when data is being used for a risk assessment.

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PAH Analytical Techniques and Impacts on Risk Assessment

  1. 1. Presented by Erik Martin, PhD, DABT 2011 SETAC Conference on Nov. 14, 2011 Co-Author: Court D. Sandau, PhDSETAC 2011 - www.chemistry-matters.com 1
  2. 2. 1. BACKGROUNDPolycyclic Aromatic Hydrocarbons
  3. 3. * * PAHs are a complex class of organic compounds containing two or more fused aromatic rings (only C and H atoms). * They are primarily formed by incomplete combustion of carbon-containing fuels - wood, coal, diesel or tobacco. * Sources * Anthropogenic: Wood burning, vehicle emissions, industry * Natural: Forest fires, volcanoesSETAC 2011 - www.chemistry-matters.com 3
  4. 4. * naphthalene acenaphthene anthracene acenaphthylene phenanthrene f luorene 2-ring 3-ring chrysene fluoranthene pyrene benzo[a]anthracene benzo[b]fluoranthene 4-ringbenzo[k]fluoranthene dibenz[a,h]anthracene benzo[a]pyrene benzo[ghi]perylene indeno[1,2,3-cd]pyrene 5-ring 6-ringSETAC 2011 - www.chemistry-matters.com 4
  5. 5. Why do we care? PAHs have been identified as a contaminant of concern at 401 National Priorities List (NPL) sites (roughly one-third of sites) and are ranked ninth on the CERCLA priority list of hazardous substances (2011).SETAC 2011 - www.chemistry-matters.com 5
  6. 6. 2. TOXIC EQUIVALENT SCHEME
  7. 7. Benzo(a)pyrene Toxic Equivalency – B(a)P TEQFor mixtures of structurally related chemicals with a common mechanism ofaction, use TEQ approach to evaluate the toxicity and assess risk.B(a)P TEQ are calculated by multiplying the soil conc. of individual PAHs by atoxic equivalency factor (TEF), and by subsequently summing the B(a)P TEQfor the entire PAH mixture (total B(a)P TEQ).TEFs are order of magnitude estimates of toxic potential as compared toB(a)P; which is given a reference value of 1. Where: TEFn = Toxic Equivalency Factor of Individual Congener Cn = Concentration of Congener in Complex MixtureSETAC 2011 - www.chemistry-matters.com 7
  8. 8. Compound [1] [2] [3] [4] [5] [6] [7] 1-Methylphenanthrene 0.001 Acenaphthene 0.001 0.001 0.001 0 Acenaphthylene 0.001 0.001 0.01 Anthanthrene 0.32 0.28 Anthracene 0.01 0.01 0.01 TEF Sets Benz[a]anthracene 0.145 0.1 0.1 0.1 0.1 0.1 0.014 [1] Krewski et al. (1989) Benzo[a]pyrene 1 1 1 1 1 1 1 [2] Nisbet & LaGoy (1992) Benzo[b]fluoranthene 0.141 0.1 0.1 0.1 0.1 0.1 0.11 Benzo[e]pyrene 0.004 0.01 0 [3] Malcolm & Dobson (1994) Benzo[ghi]perylene 0.022 0.01 0.01 0.01 0.012 [4] Kalberlah et al. (1995) Benzo[j]fluoranthene 0.1 0.1 0.045 [5] US EPA (1993) Benzo[k]fluoranthene 0.061 0.1 0.1 0.1 0.01 0.1 0.037 Chrysene 0.0044 0.01 0.01 0.01 0.001 0.1 0.026 [6] McClure & Schoeny (1995) Coronene 0.001 [7] Muller et al. (1995a,b, 1996) Cyclopenta[cd]pyrene 0.023 0.1 0.1 0.012 Dibenzo[a,e]pyrene 1 Others: Dibenz[a,c]anthracene 0.1 Dibenz[a,h]anthracene 1.11 5 1 1 1 1 0.89 OEHHA (1993) Dibenzo[a,l]pyrene 100 100 CalEPA (2005) Dibenzo[a,e]fluoranthene 1 Dibenzo[a,h]pyrene 1 1.2 Dibenzo[a,i]pyrene 0.1 Fluoranthene 0.001 0.001 0.01 Fluorene 0.001 0.001 0 Indeno[1,2,3-cd]pyrene 0.232 0.1 0.1 0.1 0.1 0.1 0.067 Naphthalene 0.001 0.001 Perylene 0.001 Phenanthrene 0.001 0.001 0 0.00064 Pyrene 0.81 0.001 0.001 0.001 0SETAC 2011 - www.chemistry-matters.com 8
  9. 9. PAH Mechanism of Toxicity NUCLEUS ⇌ AhR hsp90PAH PAH ARNT ARNT PAH AhR hsp90 CYP1A PAH AhR XREs CYP1A mRNA Other mRNAs apo–CYP1A ENDOPLASMIC X RETICULUM GT EH further PAH-OH R CYP1A metabolism Hepatocyte PAH ⇌ R = NADPH-cytochrome P450 reductase EH = epoxide hydroxylase PAH GT = glutathione transferase X = UDP-glucuronosyl transferase SETAC 2011 - www.chemistry-matters.com 9
  10. 10. 3. ANALYTICAL METHODS
  11. 11. Analytical Methods  A number of analytical methods are available to measure PAHs in various environmental media (including soil).  Examples: Gas chromatography/mass spectrometry (GC/MS) - US EPA Method 8270C - Standard analytical method High-resolution isotope dilution mass spectrometry (ID/MS) - Based on CARB429 - Less common methodSETAC 2011 - www.chemistry-matters.com 11
  12. 12. GC/MS VS. ID/MSSETAC 2011 - www.chemistry-matters.com 12
  13. 13. * Low Resolution MS Method High Resolution MS Method  US EPA Method 8270C  Modified California Method  Full scan analysis  Selected ion monitoring  No confirmation ions or ratios  IDMS quantitation  Inappropriate surrogate  Interferences are less likely standards  Isotopically labeled standards  Less sensitive method  More accurate and precise  Many versions of methodSETAC 2011 - www.chemistry-matters.com 13
  14. 14. * Many interferences exist in low MW range – Depends on matrix, cleanup method Specificity of HRMS allows better accuracy and precision Comes at a cost – 4 to 6x ($150 vs. $800) Difference in measuring 252 versus 252.30928 Benzo(a)pyreneSETAC 2011 - www.chemistry-matters.com 14
  15. 15. * Naphthalene Phenanthrene Benzo(a)pyrene * * * * * * * * F O N+ O- Nitrobenzene 2-Fluorobiphenyl p-TerphenylSETAC 2011 - www.chemistry-matters.com 15
  16. 16. *  Internal standards behave exactly like compounds being analyzed  Loss of analytes during method, included in measurement (adjust recovery)  Interferences in method, can usually be seen with standards as well  The most accurate measurement available (‘gold standard’)SETAC 2011 - www.chemistry-matters.com 16
  17. 17. 4. CASE STUDY
  18. 18. Case StudyLitigation involving a site with a long history of industrial activity(inc. tannery/hide treatment, rail operation, manufacturing facilities)Is more expensive better?Experiment: Sampled 5 locations Homogenized and split samples Sent 5 for routine PAH analysis Sent 5 for ID-HRMS analysis SRM – determine accuracy Duplicate – determine precision SETAC 2011 - www.chemistry-matters.com 18
  19. 19. *  How close are the analytical measurements to the ‘true’ values?  Assessed by measuring a sample with known PAH concentrations. - Standard Reference Material - NIST (National Institute of Standards &Technology)SETAC 2011 - www.chemistry-matters.com 19
  20. 20. Concentration (ng/g) Ac en 0.2 0.4 0.6 0.8 1.2 0 1 ap ht he Ac ne en ap ht hy le ne An th Be ra nz ce o( ne a) an th ra ce Be ne nz o( Be a) py nz re * Overestimation o( ne b) fluSETAC 2011 - www.chemistry-matters.com or Be an Certified SRM Value nz th o( en g, e h, i)p Be er nz yle o( ne k) f lu or HRMS an th en e Di Ch be ry nz se20 (a ne .h )a LRMS nt hr ac en Fl e uo ra nt he ne In Fl de uo no re (1 ne ,2 .3 Standard Reference Material -c 2- d) M py re et hy ne ln ap ht ha le ne Na ph th al en Ph e en an th re ne Py re ne
  21. 21. Concentration (ng/g) Ac en 0.2 0.4 0.6 0.8 1.2 0 1 ap ht he Ac ne en ap ht hy le ne An th Be ra nz ce o( ne a) an th ra ce Be ne nz o( Be a) py nz re * Overestimation o( ne b) fluSETAC 2011 - www.chemistry-matters.com or Be an Certified SRM Value nz th o( en g, e h, i)p Be er nz yle o( ne k) f lu or HRMS an th en e Di Ch be ry nz se21 (a ne .h )a LRMS nt hr ac en Fl e uo ra nt he ne In Fl de uo no re (1 ne ,2 .3 Standard Reference Material -c 2- d) M py re et hy ne ln ap ht ha le ne Na ph th al en Ph e en an th re ne Py re ne
  22. 22. *  Can the laboratory achieve the same analytical result repeatedly?  Assessed by evaluating blind duplicates  Field duplicate - includes sampling error  Lab duplicate - only laboratory error  Relative Percent Difference to determine differences in measurementsSETAC 2011 - www.chemistry-matters.com 22
  23. 23. PAH Duplicate Results HRMS 120 3% 8% 15% 16% 18% 17% 27% 11% RPD 100 Concentration 80 (ng/g) 60 40 20 0 BaA BaP BbF BkF CHRY FLUOR PHEN PYR LRMS 120 100 100% 92% 111% 100% 86% 94% 101% 90% RPD Concentration 80 (ng/g) 60 40 20 0 BaA BaP BbF BkF CHRY FLUOR PHEN PYRSETAC 2011 - www.chemistry-matters.com 23
  24. 24. PAH Duplicate Results HRMS 120 3% 8% 15% 16% 18% 17% 27% 11% RPD 100 Concentration 80 (ng/g) 60 40 20 0 BaA BaP BbF BkF CHRY FLUOR PHEN PYR LRMS 120 100 100% 92% 111% 100% 86% 94% 101% 90% RPD Concentration 80 (ng/g) 60 40 20 0 BaA BaP BbF BkF CHRY FLUOR PHEN PYRSETAC 2011 - www.chemistry-matters.com 24
  25. 25. Concentration (ng/g) Ac en ap 100 200 300 400 500 600 700 800 900 1000 0 Ac ht en he ap ne ht hy le Be An ne th LRMS Method HRMS Method nz ra o( ce a) ne an th Be ra nz ce Be o( ne nz a) o( pySETAC 2011 - www.chemistry-matters.com b) re Be flu ne nz or an o( th g, en Be h, e nz i)p o( er k) yle f lu ne or an th Di en be Ch e nz (a ry25 .h se )a ne nt hr Sample 1-1 ac Fl en uo e ra nt In he de ne no Fl (1 uo ,2 re 2- .3 ne M -c d) PAH Analytical Results et py hy re ln ne ap ht ha Na le ne ph th Ph al en en e an th re ne Py re ne
  26. 26. Total B(a)P TEQ 3500 3000 2500 17,278 32,542 2000 1500 1000 500 0 1-1 9-1 9-3 21-1 22-1 HRMS Method B(a)P guideline for industrial soil LRMS MethodSETAC 2011 - www.chemistry-matters.com 26
  27. 27. *  Detection limits are 200x lower with ID-HRMS  When calculating the total B(a)P TEQ, where a PAH is non-detect, ½DL is used. if high DLs then overestimate total TEQ.SETAC 2011 - www.chemistry-matters.com 27
  28. 28. HRMS LRMS g/kg TEF TEQ g/kg TEF TEQ Acenaphthene 1.37 0.001 0.00137 5 0.001 0.005 Acenaphthylene 2.56 0.001 0.00256 2.5 0.001 0.0025 Anthracene 10.3 0.01 0.103 12 0.01 0.12 Benzo(a)anthracene 32.7 0.1 3.27 60 0.1 6 Benzo(a)pyrene 34.7 1 34.7 46 1 46 Benzo(b)fluoranthene 49.0 0.1 4.9 70 0.1 7 Benzo(g,h,i)perylene 27.8 0.01 0.278 40 0.01 0.4 Benzo(k)fluoranthene 18.8 0.1 1.88 30 0.1 3 Chrysene 33.4 0.01 0.334 50 0.01 0.5 Dibenz(a.h)anthracene 6.81 5 34.05 10 5 50 Fluoranthene 60.7 0.001 0.0607 91 0.001 0.091 Fluorene 7.04 0.001 0.00704 2.5 0.001 0.0025 Indeno(1,2.3-cd)pyrene 26.2 0.1 2.62 30 0.1 3 Naphthalene 14.4 0.001 0.0144 10 0.001 0.01 Phenanthrene 48.4 0.001 0.0484 70 0.001 0.07 Pyrene 51.2 0.001 0.0512 74 0.001 0.074 Total B(a)P TEQ 82.32 116.28 % of TEQ from ½DL 0% 43%SETAC 2011 - www.chemistry-matters.com 28
  29. 29. 5. CONCLUSIONS
  30. 30. *  For measurement of PAHs, ID-HRMS provides unparalleled resolution, accuracy and precision.  Contaminated sites driven by PAH risk require the ID- HRMS method. – Sensitivity - for guidelines – Specificity - for interferences that are naturally present in samples  The only method that should be used for risk assessment, contaminated site closure, and litigation.  LRMS method should be used sparingly or used for screening purposes only.SETAC 2011 – for inquiries please visit: 30www.chemistry-matters.com
  31. 31. QUESTIONS

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