Measurement of Bromate and Haloacetic Acids In Drinking Water by IC-MS/MS

Transcription

1 Measurement of Bromate and aloacetic Acids In Drinking Water by IC-MS/MS Richard F. Jack, R. Al-orr, C. Saini, B. Joyce, C. Pohl, R. Slingsby Dionex Corporation, Sunnyvale, CA, USA Clayton Babcock Dionex Canada Limited 245 Our water is safe to drink thanks to proven chemical water purification technology. owever 2455

2 Concern for Long-term Exposure to Disinfection By-Products (DBPs) Trihalomethanes (TMs) in 1970s 1998 U.S. EPA Stage 2 DBP: seven new regulations include AA5 and bromate Trihalomethane 20.1% aloacetonitrile 2.0% Chloral ydrate 1.5% aloacetic Acids 1.0% Cyanogen Chloride 1.0% Unknown alogenated Organics 62.4% 2455 Why have a Disinfectants and Disinfection Byproducts Rule? Trihalomethanes (TM) form Liver, kidney or central nervous system problems; increased risk of cancer. - aloacetic Acids (AA5) Increased risk of cancer Bromate causes Increased risk of cancer. Chlorite Anemia; infants & young children: nervous system effects..

3 Stage 2 Disinfectants and Disinfection Byproducts Rule Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. Location Running Annual Average (LRAA) Compliance must be met at each monitoring location, not just the system drinking water average. Drinking Water Disinfection: Treatment and By-Products Disinfection byproducts are formed when disinfectants used in water treatment plants react with bromide and/or natural organic matter. Disinfection Treatment Chlorination Chlorine Dioxide Chloramine Ozonation Disinfection By-Products Trihalomethanes aloacetic Acids Chlorate Chlorite Chlorate Chlorate Bromate

4 What Are AAs? Acid Monochloro Acetic Acid Dichloro Acetic Acid Trichloro Acetic Acid Monobromo Acetic Acid Dibromo Acetic Acid Tribromo Acetic Acid Bromochloro Acetic Acid Dibromochloro Acetic Acid Dichlorobromo Acetic Acid Abbreviation * DCAA * TCAA * * DBAA * TBAA BCAA DBCAA DCBAA Chemical Formula ClC 2 CO 2 Cl 2 CCO 2 Cl CCO 2 BrC 2 CO 2 Br 2 CCO 2 Br CCO 2 BrClCCO 2 Br 2 ClCCO 2 Cl 2 ClCCO 2 pka a, 1.29 b, 1.0 c 0.6 a, 0.65 b, 0.70 c 2.87 a, 2.86 b, 2.7 c NA 0.66 NA NA NA Boiling Point C NA NA *, DCAA, TCAA,, DBAA are collectively referred to as AA U.S. EPA Method 552. Determination of aloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid Microextraction, Derivatization, and Gas Chromatography with Electron Capture Detection Method Steps: Adjust p to 0.5 then Extract with either with methyl tert-butyl ether (MTBE) or tert-amyl methyl ether (TAME) Convert AAs to their methyl esters by addition of acidic methanol and heat for two hours Separate from the acidic methanol by adding a concentrated aqueous solution of sodium sulfate Neutralize with saturated solution of sodium bicarbonate Analyze by GC/ECD: run time 25 0 min 2458

5 U.S. EPA Method 552. Reported Detection Limits Advantages: Good selectivity Low MDLs Wide applicable concentration range: µg/l Analyte DCAA Detection Limits (µg/l) % Recovery Limitations: Requires sample pretreatment Time consuming Labor intensive Subject to multiple procedural errors BCAA DBAA TCAA BDCAA CDBAA TBAA Drinking Water Matrix Sulfate in drinking water currently has a secondary maximum contaminant level (SMCL) of 250 mg/l, based on aesthetic effects (i.e., taste and odor); this regulation is not a Federallyenforceable standard, but is provided as a guideline for states and public water systems; U.S. EPA estimates that about % of the public drinking water systems in the country may have sulfate levels of 250 mg/l or greater Chloride 250 mg/l Carbonate 150 mg/l Nitrate 20 mg/l Ammonium chloride 100 mg/l (preservative) 2462

6 Notes on using MS Detection Why use an MS Detector Improved sensitivity. No pre-concentration or pre-treatment. Precautions using an MS Matrix ions interfere and cause signal suppression. Poor recoveries and detection limits Counts Counts Counts Reversed Phase Separation Salt Matrix No Matrix Acid Matrix Column: Acclaim PA µm, 2-mm ID Suppressor: ASRS MS, 2 mm Eluent: 99% formic acid (0.15%); 1% acetonitrile Flow Rate: 0.25 ml/min Temp. 0 C Injection Loop: 100 µl Detector: MSQ plus, ESI, SIM mode Probe:.5kV, 400 C Source: 5V µg/l Analytes: DCAA BCAA DBAA 10 Matrix: Acid or salt: SO mg/l; NO 10 mg/l; Cl 50 mg/l 2175

7 Recovery of Reversed Phase Separation % Recovery Recovery of AA5 in a Simulated Matrix of 2 SO 4 DCAA DBAA TCAA Sulfate (mg/l) LC-MS/MS based Methods had Problems Weaknesses of LC-MS based Methods Poor Retention and Separation from matrix ions without strong enough acids or appropriate ion-pair agent in the mobile phase» Poor Recovery» Poor sensitivity: Signal suppression by matrix ions» Poor ruggedness: No matrix diversion due to poor separation leads to source contamination which affects MS response and sensitivity AA s have very low pka s and thus will require a strong acid to neutralize the carboxylic acids. Presence of strong acids (volatile) and/or ion-pair agents in mobile phases leads to» Poor Separation in high matrix samples» Poor sensitivity: Due to strong signal suppression from acid or ion-pair agents» Poor ruggedness: contaminate source with ion pair agent and acid» Strong volatile acids can still damage the MS_ESI source Poor performance in strong matrix 1. Recovery 2. %RSD. Detection limits An IC/MS method was a possible solution 2461

8 Method Objectives Goals: Separate all nine haloacetic acids and bromate Eliminate derivatization or pretreatment step Eliminate preconcentration Minimize matrix effects» Improve separation efficiency and resolution» Minimize MS signal suppression by matrix ions Achieve MDL of < 0.5 µg/l with recovery of > 90% Isotope labeled internal standards Solution: IC-MS/MS A new AS24 column» Significantly higher capacity than currently available ion chromatography columns Mass spectrometry as a detector:» Sensitive detection No preconcentration» Selective Limited matrix interference 2461 IC-MS/MS ardware Arrangement MSQ ICS

9 Flow Diagram with Matrix Diversion Column KO 0. ml/min Suppressor MD Ports, 4, and 5 Are Plugged CD Waste 1 MD 2 Valve GND 6 DP Pump2 100% MeCN 0. ml/min ESI Capillary MSQ inlet Cone In this configuration the DP-Pump 2 delivers acetonitrile to the MS/MS continuously; the matrix diversion valve is used to divert sample matrix to waste and then send the analytical stream to the MS instrument; the analytical stream is mixed with solvent in a high-efficiency static-mixing tee before entering the mass spectrometer 246 RFIC ydroxide Eluent Generation KO Electrolytic Chamber EluGen KO Cartridge K + Electrolyte Reservoir K + Cation- Exchange Membrane [KO] α Current Flow Rate 2 O KO Eluent KO concentration = Proportional to the current divided by flow rate

10 The Role of Suppression Eluent (KO) Sample F -, CI -, SO Without Suppression Counter Ions F CI SO 2-4 Analytical Column µs Anion Suppressor Waste + Na + NaF, NaCl, Na 2 SO 4 in KO Waste Time With Suppression CI F SO O 2 O µs F, CI, 2 SO 4 in Water Time 1294 Development of IC-MS/MS Analysis Method ESI-MS/MS conditions Optimized for each analyte» Fragmentation voltage» Collision energy Optimized ESI conditions» Temperature» Gas flow rate Choose internal standard(s) Stable-isotopically labeled No interference with analytes at detection m/z Select a high resolution separation chemistry Pursue detection limit and recovery studies 2465

11 100 Recovery of in 10 ppb 1 C- (ISTD) Concentration (ppb) C Internal Standard % Recovery Recovery of (ISTD) 1 C- in 10 ppb 1 C- Concentration (ppb) % Recovery Relative Abundance m/z Relative Abundance C- ISTD m/z 2466 Overview of Ion Chromatography Columns Evaluated Current IC columns: Why Sample Prep is needed? IonPac AS19 IonPac AS20 New IonPac AS24 column 2467

12 Problem: igh Ionic Strength Matrix Poor Sensitivity, Poor Recovery 2,500 Counts ppb Matrix No Matrix 5 10 Minutes Column: IonPac AS20, 2 x 250 mm Matrix: SO ppm NO 10 ppm N 4 Cl 100 ppm Cl 50 ppm Analyte 500 ppt 95.4 % Recovery 750 ppt 1000 ppt ppt 97.9 Starting hydroxide concentration is 4 mm 0 15 min DCAA Bromate Poor recovery Below Det TCAA Below Det DBAA Ion Chromatography: Comparison of Column Performance for AA Application Columns investigated: AS19 and AS20 Poor recovery and poor sensitivity in presence of matrix Narrow window for matrix diversion Inadequate capacity New AS24 column Significantly higher capacity Large time window for matrix diversion» Allows resolution of analytes in the presence of 250 ppm chloride Baseline resolution of SO42, TCAA, and DBCAA» Able to separate nine AAs 2469

13 Preparation and Anatomy of AS24 Resin TEM of Bead Crossection Cartoon of Surface Modification SEM of SMP Bead 2470 Summary of the IonPac AS24 2 mm Column Significantly high-capacity column No significant peak broadening with high matrix Good recovery IC-MS/MS: MDLs < 0.5 ppb for each of the AA5 and less than 1.0 ppb for each of the other AAs with matrix Low column bleed Wide enough window for matrix diversion

14 4.2e4 Intensity, cps e4 Intensity, cps mm IonPac AS24 Column: AA Separation Matrix Diversion Window 1 2 Cl - Br - NO 2- SO 4 2- Matrix: SO ppm NO 20 ppm N 4 Cl 100 ppm Cl 250 ppm DI Water Time, min Column: 2 mm Prototype Suppressor: ASRS MS, 2 mm Flow Rate: 0.0 ml/min Solvent: 0.20 ml/min MeCN Temperature. 15 C Injection Loop: 100 µl Detector: API 2000, MRM mode KO Gradient: Conc. (mm) Time (min) Peaks: 1. Chloroacetic acid ppb 2. Bromoacetic acid 2 ppb. Dichloroacetic acid ppb 4. Bromochloroacetic acid 2 ppb 5. Dibromoacetic acid 1 ppb 6. Trichloroacetic acid 1 ppb 7. Bromodichloroacetic acid 1 ppb 8. Chlorodibromoacetic acid 5 ppb 9. Tribromoacetic acid 10 ppb 247 Separation and Detection of Bromate Using IonPac AS24 2 mm Column 2 Bromate Column: AS 24 mm Prototype Suppressor: ASRS MS, 2 mm Flow Rate: 0.0 ml/min Solvent: 0.20 ml/min MeCN Temp. 15 C Injection Loop: 100 µl Detector: API 2000, MRM mode KO Gradient: Conc. (mm) Time (min) Intensity, cps 1 Peaks: 1. Chloroacetic acid 0. ppb 2. Bromate 0. ppb. Bromoacetic acid 0. ppb Time, min 2472

15 5,000 Effect of the Matrix on Recovery of AA Using IonPac AS24 Column 1.5 ppb Counts mg/l SO 4 2, 250 mg/l Cl, 100 mg/l N 4 Cl, 40 mg/l NO 100 mg/l SO 4 2, 100 mg/l Cl, 100 mg/l N 4 Cl, 20 mg/l NO Area = 1297 Area = No Matrix Area = 142, Significantly higher-capacity column No significant peak broadening Good recovery Low column bleed 1, ppt 250 mg/l SO 4 2, 250 mg/l Cl, 100 mg/l N 4 Cl, 40 mg/l NO 100 mg/l SO 4 2, 100 mg/l Cl, 100 mg/l N 4 Cl, 20 mg/l NO Area = 18 Area = 154 No Matrix 1 Area = Minutes 2474 Matrix Effects: Recovery and Retention Times Stability for AAs Using IonPac AS24 Column Analyte DCAA BCAA DBAA TCAA BDCAA CDBAA TBAA Recovery and Shifts in Retention Times for All Nine AAs Using the IonPac AS24 Prototype 250 X 2 mm Anion Exchange Column Concentration µg/l Area x10 4 DI Water N = Area x10 4 Matrix N = Recovery R.T. (min) DI Water N = R.T. (min) Matrix N = Shift (min)

16 MDLs for AA and Bromate in D.I. Water and Simulated Matrix Analyte DCAA Bromate TCAA BCAA DBAA DCBAA DBCAA TBAA D.I. 2 O MDL n=7, ng/l IC-MS/MS *Simulated Matrix MDL n=7, ng/l IC-MS/MS * Simulated Matrix: SO mg/l; Cl 250 mg/l; NO 20 mg/l; N 4 Cl 100 mg/l 2476 Conclusions With new IonPac AS24 column Separation of all nine haloacetic acids and bromate was achieved in drinking water matrix Separation in less than 60 minutes Direct injection : no derivatization or sample pretreatment is required, Fully automated MS/MS as a detector: igh sensitivity Specific (m/z) MDL < 0.5 ppb for AA5 and bromate; < 1 ppb for all other non regulated AAs Recovery values > 90% 2477