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Low-Level Perchlorate Analysis in Groundwater by Improved IC & LC/MS/MS

Low-Level Perchlorate Analysis in Groundwater by Improved IC & LC/MS/MS. March–April 2003 Presented by STL Denver. Presentation Outline . Background Methods currently used for perchlorate Methods & equipment for this study

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Low-Level Perchlorate Analysis in Groundwater by Improved IC & LC/MS/MS

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  1. Low-Level Perchlorate Analysis in Groundwater by Improved IC & LC/MS/MS March–April 2003 Presented by STL Denver

  2. Presentation Outline • Background • Methods currently used for perchlorate • Methods & equipment for this study • Performance Characteristics: selectivity, sensitivity, precision, and accuracy • Plans for future work

  3. Perchlorate Background • Used in some consumer products • Primarily produced for solid rocket fuel and munitions • Found in groundwater near production, test facilities, and other places of use • Persistent and mobile in groundwater

  4. What Is The Concern With Perchlorate? • Perchlorate interferes with iodide uptake in the thyroid gland • Recent studies indicate developmental and growth effects at low concentrations, particularly to the development of the nervous system • Potential carcinogen • Perchlorate has been found in 22 states, including Colorado

  5. Current Methods for Perchlorate TechniqueApplication • Ion-selective electrode (ISE) • Field screening • Colorimetric • NIOSH air • Capillary electrophoresis (CE) • FBI forensics • Ion chromatography (IC) • EPA water, 314.0 • Electrospray ionization • USAF & USEPA mass spectrometry (ESI-MS) research labs • Growing interest in DOD and DOE

  6. Evolution to Better Environmental Methods Driven by need for: 1) Sensitivity • Older “standard” 314.0 MDL = 1.5 ug/L • The action level for perchlorate in California and Texas is 4 ug/L • The proposed Federal limit is 1 ug/L when fetuses and newborns are of concern • Require quantitative limits < 1 ug/L • Require detection limits < 0.5 ug/L • Method 314.0 can meet these requirements

  7. Evolution to Better Environmental Methods (Continued) 2) Selectivity / Ruggedness • Current IC methods approved for drinking water • STL Denver’s LC/MS/MS method works well in reagent water 3) How well do the methods work in groundwater / real-world field samples?

  8. Methods for This Study 1. Ion Chromatography (IC) • Improved version of EPA Method 314.0, Revision 1, Nov. 1999 • EPA approved method for drinking water only • Data for this study was provided by STL Denver

  9. What Is Improved IC?(Improved Method 314.0) • Large volume injector - 1,000 uL • Dionex AG11 guard column • Dionex AS11 separation column • Dionex AMMS (Anion Micro Membrane Suppressor) chemical suppressor in external mode─Biggest Improvement • Still within scope of Method 314.0

  10. Methods for This Study(Continued) 2. Liquid Chromatography/Mass Spectrometry (LC/MS) 3. Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) • Magnunson et.al. (EPA National Risk Management Research Laboratory), Analytical Chemistry, Vol. 72, No. 1; January1, 2000 • E. Urbansky (EPA National Risk Management Research Laboratory), Critical Reviews in Analytical Chemistry, 2000, CRC • Data for this study was provided by STL Denver

  11. Groundwater (GW) Used for Validation Study Groundwater from Missouri landfill General water quality parameters: pH = 8.0 Conductivity = 1,600 uS TDS = 1,100 mg/L Alkalinity = 440 mg/L (as CaCO3) Sulfate = 460 mg/L Chloride = 75 mg/L

  12. Groundwater Spikes Prepared for Study ICLC/MS/MS 0.1 ug/L: 8 replicates 8 replicates 0.4 ug/L: 8 replicates 8 replicates 1.0 ug/L: 8 replicates 8 replicates 2.5 ug/L: 8 replicates 8 replicates 5.0 ug/L: 8 replicates 8 replicates

  13. Performance Characteristics 1. Selectivity

  14. Equipment Configuration

  15. Equipment Configuration(Continued)

  16. Natural Isotopes of Chlorine Provide Confirmation for LC/MS/MS Molecular ions analyzed in first stage: ClO4- = Cl35+4O16 = m/z 99, 75.5% abundance = Cl37+4O16 = m/z 101, 24.5% abundance Daughter ions analyzed in third stage: ClO3- = Cl35+3O16 = m/z 83 = Cl37+4O16 = m/z 85

  17. Selectivity • By monitoring 4 ions and ion ratios, LC/MS/MS is more selective than IC • EPA Office of Drinking Water is working on Method 314.1, a dual column method, to avoid false positive results • What about IC/MS methodology?

  18. Performance Characteristics 2. Sensitivity

  19. Working Range

  20. 1.0 ppb IC Standard in DI Water Blow Up Signal:Noise  16 40CFR MDL = 0.2 ug/L

  21. 1.0 ppb IC Standard in Ground Water Blow Up Signal:Noise (S:N)  12 40CFR136 MDL = 0.6

  22. 5ppb S:N = 10 2 ppb not detected IC Detection Limit Near Max. Conductivity Threshold (MCT)

  23. Effect of Ionic Strength on IC Background (20 ppb perchlorate)

  24. Signal:Noise = 11 40CFR136B MDL = 0.06 ug/L 0.1 ppb LC/MS/MS - m/z 83in DI Water

  25. 0.1 ppb LC/MS/MS - m/z 85in DI Water Similar sensitivity for confirmation ion

  26. 0.1 ppb LC/MS/MS Standard in Ground Water Signal:Noise  7 40CFR136B MDL = 0.056 ug/L

  27. Detection Limits in Groundwater(32% of MCT) IC = 0.41 ug/L LC/MS/MS = 0.056 ug/L

  28. Sensitivity • LC/MS/MS is more sensitive than LC/MS • LC/MS/MS sensitivity is little affected by changes in ionic strength • IC sensitivity degrades by 10x over conductivity range prescribed by method • EPA Office of Drinking Water working on Method 314.1 to include pre-treatment options to remove interferences affecting IC sensitivity

  29. Performance Characteristics 3. Method Precision

  30. LC/MS/MS Precision in Groundwater

  31. IC Precision in Groundwater * Includes Eight Replicates

  32. Performance Characteristics 4. Method Bias

  33. Technique for Controlling Effect of Ionic Strength – Method 314.0 • Determine maximum conductivity threshold (MCT), i.e., concentration that produces > 80% recovery • Dilute samples to conductance < MCT • Significant problem remains • Accuracy is controlled, but sensitivity is not • Some labs evaporate samples to get lower theoretical MDL ─ STL Denver does not

  34. Effect of Ionic Strength on LC/MS/MS Analysis (5 ppb perchlorate)

  35. Technique for Controlling Effect of Ionic Strength – LC/MS/MS • Standard addition for each sample • High degree of linearity and precision allow control of accuracy with standard additions (possible correction based on matrix spike recoveries) • High degree of precision ensures no significant loss of sensitivity • EPA is encouraging Cambridge Isotopes to make an O18 labeled perchlorate – Internal Standard

  36. Recovery In Groundwater

  37. Summary of Method Performance in Groundwater Improved ICLC/MS/MS Working Range: 1-40 ug/L 0.1-10 ug/L Linearity, r: >0.995 >0.995 MDL in GW: 0.61 ug/L 0.056 ug/L RSD: 6-17 % 6-12 % Recovery from: 0-108% 62-101% DI MDL to Mid-range

  38. Conclusions Improved Method 314.0 is method of choice where sensitivity and selectivity are adequate: • EPA approved • 4x more sensitive than older 314.0 • Accurate in samples with high ionic strength • But, sensitivity  1 / ionic strength

  39. Conclusions LC/MS/MS is a more powerful method • Includes confirmation capability • 10x more sensitive than improved 314.0 in groundwater used for study • Sensitivity less affected by ionic strength • Because of ionization suppression, requires standard addition per sample • Good precision and linearity makes method of additions practical

  40. Future Method Improvements • Dual column IC • Precolumn cleanup techniques • Barium columns • Perchlorate-specific resins • Isotope dilution technique for LC/MS/MS • STL Denver to assist in EPA’s development of MS method • STL Denver is working with Dionex on Perchlorate by IC/MS/MS

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