IMPROVED IDENTIFICATION OF PESTICIDES USING ATMOSPHERIC PRESSURE GAS CHROMATOGRAPHY MASS SPECTROMETRY

Transcription

1 IMPROVED IDENTIFICATION OF PESTICIDES USING ATMOSPHERIC PRESSURE GAS CHROMATOGRAPHY MASS SPECTROMETRY Kelly Dorweiler, Senior Scientist Chemical Residue Method Development North American Chemical Residue Workshop Wednesday July 23, 2014

2 ABOUT MEDALLION LABS Located at the General Mills James Ford Bell Technical Center in Golden Valley, MN Medallion Labs has been analyzing food products since 1974 ISO accredited since 2008 Pesticide Analysis in-scope

3 OUTLINE EI vs. APGC How it works Theory Examples Method development progress Pesticides and matrices evaluated Concluding remarks

4 EI VERSES APGC Electron-Impact (EI) Hard Ionization Well established Published Library (NIST) Source/Column maintenance requires significant downtime System must be dry Atmospheric Pressure Ionization (API) Soft Ionization Variable Fragment patterns Complements traditional EI instrumentation Faster source and column maintenance System does not require dryness!

5 APGC IONIZATION Charge Transfer Dry conditions No modifier Increased fragmentation Excellent for non-polar compounds (e.g. chlorinated pesticides, PCBs) Proton Transfer Wet conditions Modifier required Better retention of molecular ion Excellent for moderately polar compounds (e.g organophosphates)

6 Temperature C INSTRUMENTATION Sample Introduction: Gerstel ATEX GC Chromatograph: Agilent Inlet and GC Programs Analytical Column: Rxi-5ms 20m 0.25 mmid, 0.25 m HRMS Q-TOF: Waters Xevo G2-S APGC Conditions Water modifier ( Wet ) Corona 2 A Sampling Cone 35 V Source Temperature 150 C Source Offset 80 Cone Gas 150 L/hr Auxiliary Gas 400 L/hr QTOF Method MS E Centroid Positive API Resolution Mode amu mass range Scan Time 0.1 second Low Energy collision energy 6 V High Energy collision energy V TDU Program TDU Floating Temperature CIS Inlet Program Time (min) CIS Floating Temperature GC Oven Temperature Program TOF / QTOF Data acquired in a single run

7 APGC CHARGE TRANSFER 2 GC Transfer Line Mass Spectrometer Corona Needle Suggested mechanism proposed by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45,

8 APGC CHARGE TRANSFER e - 2 e e - 2 e - e - 2 Corona Needle Discharge Suggested mechanism proposed by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45,

9 APGC CHARGE TRANSFER + 2e e - + N 4 + 2e - N 4 + 2e - 2e - 2 Suggested mechanism proposed by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45,

10 APGC CHARGE TRANSFER + M 2 M + 2 M N N 4 + M M 2 Suggested mechanism proposed by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45,

11 APGC CHARGE TRANSFER M M + M M + 2 M + Suggested mechanism proposed by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45,

12 APGC CHARGE TRANSFER Benzoylprop-ethyl: Strong Molecular Ion Exact Mass:

13 APGC CHARGE TRANSFER Aldrin: Small Molecular Ion Fragmentation in source Exact Mass:

14 APGC PROTON TRANSFER Proposed mechanism suggested by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45, Modifier

15 APGC PROTON TRANSFER e - 2 e - N e - 2 N 2 2 e - e - e - e - e - 2 Proposed mechanism suggested by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45, Corona Needle Discharge

16 APGC PROTON TRANSFER + H + OH - 2e - N 4 + N 4 + e - N + 4 2e - H + OH - 2e - H + OH - H + OH - H + OH - 2e - e - 2e - + e - Proposed mechanism suggested by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45, Nitrogen Gas Radical Formation

17 APGC PROTON TRANSFER H + OH - e N H + OH N 2 2 H + OH - e - H + OH - H + OH - e Proposed mechanism suggested by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45, Water Radical Formation

18 APGC PROTON TRANSFER H 3 O + +OH 2e - H 3 O + 2 +OH H 3 O + 2 OH - 2e - 2 H 3 O + OH - 2e - +OH H 3 O + Proposed mechanism suggested by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45, Hydronium/Hydroxide Radical Formation

19 APGC PROTON TRANSFER +OH 2 H 3 O + H 3 O M + N OH - 2 H 3 O + M N 2 2 OH - +OH +OH M H 3 O + H 3 O + 2 Proposed mechanism suggested by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45, Analyte Introduction

20 APGC PROTON TRANSFER +OH MH + H 3 O + 2 OH - +OH 2 MH + 2 MH + +OH H 3 O + OH - Proposed mechanism suggested by Portolés, T. et. al. J. Mass. Spectrom. 2010, 45, Analyte Protonation

21 APGC PROTON TRANSFER Endosulfan- : Strong Protonated Ion Exact Mass:

22 APGC METHOD DEVELOPMENT Comprehensive pesticide screen: APGC vs. EI? APGC: Dry vs. Wet? APGC-MS vs. LC-MS? Not one technique is suited for every analyte or matrix Leverage multiple MS technologies to achieve best overall selectivity/sensitivity GCTOF/QTOF GCQQQ LCTOF/QTOF LCQQQ

23 PESTICIDES/CONTAMINANTS UNDER EVALUATION 1,2,3,4-Tetrachlorobenzene Carfentrazone-ethyl Dicloran Fludioxonil o,p-ddd 1,2,3,5-Tetrachlorobenzene Chinomethionate Dieldrin Flufenacet o,p-dde 1,2,3,6-Tetrahydrophthalimide Chlorbenside Diethatyl-Ethyl Fluroxypyr-meptyl o,p-ddt 1,2,4,5-Tetrachlorobenzene Chlorbufam CARBAMATES Diflufenican Fluometuron Oxadiazon 1-Naphthol Chlordane-cis Dimethametryn Fluorochloridone Oxadixyl 2,3,5,6-Tetrachloroaniline Chlordane-trans Diphenamid Flurtamone Oxyflourfen 2,4-Dichlorobenzophenone ORGANOHALOGENS Chlordene-trans Diphenylamine Folpet Parathion 2,3,5,6-Tetrachloroanisole Chlordimeform Endosulfan alpha Fosthiazate PCB 18 2,6-Diisopropylnaphthalene Chlorethoxyfos Endosulfan beta Fuberidazole PCB 52 2,4-Dichlorobenzophenone Chlorfenapyr Endosulfan ether Haloxyfop-methyl PCB 153 ORGANONITROGENS 2-Phenylphenol Chlorfenson Endosulfan sulfate Heptachlor Pencycuron 3-Methyl-4-nitrophenol Chlorfenvinphos Endrin Heptachlor epoxide Pentachloroaniline 3,4-Dichloroaniline Chlorflurenol methyl ester Endrin aldehyde Hexachlorobenzene Pentachloroanisole 4,4-Dichlorobenzophenone ORGANOPHOSPHATES Chloridazon Endrin ketone Hydroprene Pentachlorobenzene Akton Chlornitrofen Ethalfluralin Iodofenphos Pentachloronitrobenzene Alachlor Chlorobenzilate Ethoprophos Iprovalicarb Pentachlorobenzonitrile Aldrin Chloropropylate PYRETHROIDS Ethoxyquin Isocarbamid Pentachlorothioanisole Benalaxyl Chloroneb Etofenprox Isopropalin Perthane Benfluralin Chlorothalonil Etridiazole Isoprothiolane Phenmedipham Benodanil Chlorpyrifos-methyl Famfur Isoxaben Phthalimide Benoxacor Chlorthal-dimethyl Fenamiphos sulfoxide Isoxadifen-ethyl Piperonyl Benzoylprop-ethyl Chlorthiophos Fenchlorphos Isoxaflutole Piperophos BHC alpha Clodinafop-propargyl Fenchlorphos-oxon Leptophos p,p-ddd BHC beta Cyanophos Fenfuram Mefanacet p,p-dde BHC delta Cycloate Fenitrothion Mefenpyr-diethyl o,p-ddt BHC gamma Cyfluthrin Fenpropathrin Mepanipyrim p,p-methoxychlor Bifenthrin Cyhalofop-butyl Fenpropimorph Mepronil Procymidone Boscalid Cyhalothrin Fenson Metoxuron Profluralin Bromacil Cypermethrin Fenthion Mirex Propanil Bromophos Cyphenothrin Fenvalerate Monuron Propazine Bromopropylate Deltamethrin Fipronil Neburon Prothiofos Bromuconazole Desmetryn Fipronil desulfinyl Nitrapyrin Pyracarbolid Bupirimate Dicapthon Fipronil sulfide Nitrofen Pyrazophos Captan Dichlobenil Fipronil sulfone Nitrofluorfen Pyridaphenthion Captafol Dichlofenthion Flamprop-methyl Nonachlor-cis Pyrifenox Carbophenothion Diclofop-methyl Fluchloralin Nonachlor-trans S-Bioallethrin

24 MATRICES EVALUATED Strawberry Orange Citrus Peel Spinach RTE Multi-Grain Cereal Corn Gluten Feed Refrigerated Pie Crust Pinto bean, dried Flaxseed Soybean, dried

25 EXTRACTION METHOD Modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) for cereal grains, high fat, high protein matrices Modified QuEChERS for produce (uses same dspe cleanup as grain) method) Weigh gram high Grains/high fat samples: 1 fat/dry matrix in 50 ml tube hour shake Weigh 15 gram produce in 50 ml tube Add IS and spike; wait 30 minutes Add H2O (10-15 ml) and MeCN (10 ml) to high fat/dry matrix sample Add 15 ml MeCN w/ 1% Acetic Acid Dry Legumes: 2 hour shake Produce: No shake required Add MgSO4/NaCl (4g:1g) to high fat/dry matrix sample Add MgSO4/NaOAc (6g:1.5g) to produce Shake/ vortex for 1 minute (minimum) Centrifuge rpm for 5 minutes Deliver 3 ml extract into dspe tube: MgSO4/PSA/C18 (450 mg : 450 mg : 150 mg) Vortex for 1 minute Centrifuge rpm for 1 minute Add check std to extract and filter Analyze by APGC-QTOFMS J. Agric. Food Chem ,

26 FENVALERATE - EI VS. APGC Fenvalerate in navy bean: 400 ng/g Caliper - sample "navy bean exact mms:1", s to s s to s Time (s)

27 FENVALERATE - EI VS. APGC Fenvalerate concentration: ng/g

28 CYPERMETHRIN EI VS. APGC

29 CYPERMETHRIN EI VS. APGC Solvent Standard: 400 ng/g Soybean MMS: 200 ng/g Time (s) Time (s) Caliper - sample "solvent std:1", s to s s to s Caliper - sample "soybean mms:1", s to s s to s

30 CYPERMETHRIN EI VS. APGC Cypermethrin Cyfluthrin

31 CYPERMETHRIN - EI VS. APGC Function 1: TOF data Retention of protonated ion; improved selectivity Function 1: TOF data Moderate fragmentation; isolation of major qualifier Function 2: QTOF data High fragmentation; indistinguishable from matrix Cyfluthrin Cypermethrin

32 ANALYTE/MATRIX MASS RESOLUTION Chloroneb accurate mass helps resolve matrix issues Doublet peak containing co-extractive at 9.64 min and Chloroneb at 9.66 min with unit mass resolution Shoulder peak containing coextractive in front of Chloroneb with unit mass resolution Co-extractive mass Chloroneb mass Co-extractive mass Chloroneb mass Theoretical Isotope model Theoretical Isotope model Single peak containing only Chloroneb at 9.66 min with 20 mda mass resolution Single peak containing only Chloroneb at 9.66 min with 20 mda mass resolution

33 ANALYTE/MATRIX MASS RESOLUTION Chloroneb false positive in clean flaxseed sample Doublet peak containing co-extractive at 9.64 min and Chloroneb at 9.66 min with unit mass resolution This is a co-extractive contaminant peak, not Chloroneb that shows up with unit mass resolution Co-extractive mass Chloroneb mass Theoretical Isotope model Single peak containing only Chloroneb at 9.66 min with 20 mda mass resolution Matrix resolved at 20 md unit mass positive is actually a false positive

34 NON-POLAR COMPOUNDS IN A WET SYSTEM Primary PCB 52: ng/g spikes (current LOQs) Secondary Primary Tecnazene: ng/g spikes (current LOQs) Secondary

35 CONCLUDING REMARKS APGC useful identification tool Particularly helpful for complex matrices Limitations exist Moisture content in source will change molecular ion intensities and fragmentation Complements other traditional MS technologies GC-EI-MS APGC-MS LC-MS HRMS provides additional specificity QQQ also suitable option High Through-put friendly Reduces false positives fewer reruns required Faster maintenance

36 ACKNOWLEDGEMENTS General Mills/Medallion Laboratories Heather Larson Steve House Todd Jensen Brett Post Laura Marshak Waters Adam Ladak Peter Randles

37 THANK YOU!