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Leaders in Environmental Testingwww.stl-inc.com Low-Level Perchlorate Analysis in Groundwater by Improved IC & LC/MS/MS March–April 2003 Presented by STL.

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Presentation on theme: "Leaders in Environmental Testingwww.stl-inc.com Low-Level Perchlorate Analysis in Groundwater by Improved IC & LC/MS/MS March–April 2003 Presented by STL."— Presentation transcript:

1 Leaders in Environmental Testingwww.stl-inc.com Low-Level Perchlorate Analysis in Groundwater by Improved IC & LC/MS/MS March–April 2003 Presented by STL Denver

2 Leaders in Environmental Testingwww.stl-inc.com 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 Leaders in Environmental Testingwww.stl-inc.com  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 Perchlorate Background

4 Leaders in Environmental Testingwww.stl-inc.com  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 What Is The Concern With Perchlorate?

5 Leaders in Environmental Testingwww.stl-inc.com Current Methods for Perchlorate Technique Application Ion-selective electrode (ISE)Field screening ColorimetricNIOSH air Capillary electrophoresis (CE)FBI forensics Ion chromatography (IC)EPA water, Electrospray ionizationUSAF & USEPA mass spectrometry (ESI-MS)research labs Growing interest in DOD and DOE

6 Leaders in Environmental Testingwww.stl-inc.com Evolution to Better Environmental Methods Driven by need for: 1) Sensitivity –Older “standard” 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 can meet these requirements

7 Leaders in Environmental Testingwww.stl-inc.com 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 Leaders in Environmental Testingwww.stl-inc.com Methods for This Study 1. Ion Chromatography (IC) –Improved version of EPA Method 314.0, Revision 1, Nov –EPA approved method for drinking water only –Data for this study was provided by STL Denver

9 Leaders in Environmental Testingwww.stl-inc.com 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 Leaders in Environmental Testingwww.stl-inc.com 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; January 1, 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 Leaders in Environmental Testingwww.stl-inc.com 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 Leaders in Environmental Testingwww.stl-inc.com Groundwater Spikes Prepared for Study ICLC/MS/MS 0.1 ug/L: 8 replicates8 replicates 0.4 ug/L: 8 replicates 8 replicates 1.0 ug/L: 8 replicates8 replicates 2.5 ug/L: 8 replicates 8 replicates 5.0 ug/L: 8 replicates 8 replicates

13 Leaders in Environmental Testingwww.stl-inc.com Performance Characteristics 1. Selectivity

14 Leaders in Environmental Testingwww.stl-inc.com Equipment Configuration

15 Leaders in Environmental Testingwww.stl-inc.com Equipment Configuration (Continued)

16 Leaders in Environmental Testingwww.stl-inc.com Natural Isotopes of Chlorine Provide Confirmation for LC/MS/MS Molecular ions analyzed in first stage: ClO4- = Cl 35 +4O 16 = m/z 99, 75.5% abundance = Cl 37 +4O 16 = m/z 101, 24.5% abundance Daughter ions analyzed in third stage: ClO3- = Cl 35 +3O 16 = m/z 83 = Cl 37 +4O 16 = m/z 85

17 Leaders in Environmental Testingwww.stl-inc.com 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 Leaders in Environmental Testingwww.stl-inc.com Performance Characteristics 2. Sensitivity

19 Leaders in Environmental Testingwww.stl-inc.com Working Range

20 Leaders in Environmental Testingwww.stl-inc.com 1.0 ppb IC Standard in DI Water Blow Up Signal:Noise  16 40CFR MDL = 0.2 ug/L

21 Leaders in Environmental Testingwww.stl-inc.com 1.0 ppb IC Standard in Ground Water Blow Up Signal:Noise (S:N)  12 40CFR136 MDL = 0.6

22 Leaders in Environmental Testingwww.stl-inc.com IC Detection Limit Near Max. Conductivity Threshold (MCT) 2 ppb not detected 5ppb S:N = 10

23 Leaders in Environmental Testingwww.stl-inc.com Effect of Ionic Strength on IC Background (20 ppb perchlorate)

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

25 Leaders in Environmental Testingwww.stl-inc.com 0.1 ppb LC/MS/MS - m/z 85 in DI Water Similar sensitivity for confirmation ion

26 Leaders in Environmental Testingwww.stl-inc.com 0.1 ppb LC/MS/MS Standard in Ground Water Signal:Noise  7 40CFR136B MDL = ug/L

27 Leaders in Environmental Testingwww.stl-inc.com Detection Limits in Groundwater (32% of MCT) IC = 0.41 ug/L LC/MS/MS = ug/L

28 Leaders in Environmental Testingwww.stl-inc.com 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 to include pre-treatment options to remove interferences affecting IC sensitivity

29 Leaders in Environmental Testingwww.stl-inc.com Performance Characteristics 3. Method Precision

30 Leaders in Environmental Testingwww.stl-inc.com LC/MS/MS Precision in Groundwater Test No. *True Value (ug/L) RSD (%)

31 Leaders in Environmental Testingwww.stl-inc.com IC Precision in Groundwater Test No. *True Value (ug/L) RSD (%) * Includes Eight Replicates

32 Leaders in Environmental Testingwww.stl-inc.com Performance Characteristics 4. Method Bias

33 Leaders in Environmental Testingwww.stl-inc.com Technique for Controlling Effect of Ionic Strength – Method  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 Leaders in Environmental Testingwww.stl-inc.com Effect of Ionic Strength on LC/MS/MS Analysis (5 ppb perchlorate)

35 Leaders in Environmental Testingwww.stl-inc.com 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 O 18 labeled perchlorate – Internal Standard

36 Leaders in Environmental Testingwww.stl-inc.com Recovery In Groundwater

37 Leaders in Environmental Testingwww.stl-inc.com Summary of Method Performance in Groundwater Improved ICLC/MS/MS Working Range:1-40 ug/L ug/L Linearity, r:>0.995>0.995 MDL in GW:0.61 ug/L0.056 ug/L RSD:6-17 % 6-12 % Recovery from: 0-108%62-101% DI MDL to Mid-range

38 Leaders in Environmental Testingwww.stl-inc.com Conclusions  EPA approved  4x more sensitive than older  Accurate in samples with high ionic strength  But, sensitivity  1 / ionic strength Improved Method is method of choice where sensitivity and selectivity are adequate:

39 Leaders in Environmental Testingwww.stl-inc.com Conclusions LC/MS/MS is a more powerful method  Includes confirmation capability  10x more sensitive than improved 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 Leaders in Environmental Testingwww.stl-inc.com 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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