Multi-Residue Pesticide Methodologies. Frans Schoutsen

Transcription

1 Multi-Residue Pesticide Methodologies Frans Schoutsen

2 Why Pesticide Analysis? Extensively used in agriculture to control pests & improve yields More than 1000 different active substances used Thoroughly tested and evaluated before approval BUT Sometimes not applied in accordance with intended purpose Banned pesticides still used in some countries Signicant public concerns about pesticide use Regulatory requirements: Regulation 396/ pesticides in variety of crops 2 2

3 Pesticide Facts 2001 WW Pesticide usage 2006, UK mygraphresults.cfm 3 3

4 EU Pesticide Residue Regulations Until 1 September 2008 legislation only partially harmonized EU- MRLs ± 250 pesticides National MRLs ± 850 pesticides 76/895/EEC (fruits and vegetables) 86/362/EEC (cereals) 86/363/EEC (animal products) 90/642/EEC (fruits and vegetables) No harmonized risk assessment for EU consumers, Trade problems Regulation 396/2005 > 490 pesticides > MRLs General MRL 0.01 mg/kg 4 4

5 Workflow for Analysis of Pesticide Residues 5 5

6 Challenges of Residue Analysis Sample variability (matrix) Compound different charecteristics Number of samples Number of analytes monitored Low levels controlled ( <10 ng/g ) Fast response required 6 6

7 Screening Methods Preferred Screening method to identify non-compliant samples Most screening methods (e.g. ELISA) focus on single analytes ONLY instrumental screening give multi residue capability Positive sample Confirmatory analysis 7 7

8 Sample Preparation Issues Losses of a number of pesticides during sample processing at ambient temperatures may occur: bitertanol, dichlofluanid, captan, chlorothalonil Solidify with solid CO2 Homogenization of frozen sample Fussell et al. (2007) Food Additives & Contam., 24:

9 Cryogenic Milling Effect on Pesticide Levels Fussell, et al. (2007) Food Additives & Contam., 24:

10 Former Pesticide Multi-Residue Method Setup Extraction Acetonitrile, Ethyl acetate, Methanol... Clean-up GPC, SPE, LLE, LC QuEChERS today Determination GC, LC, GC/MS, LC/MS, GC/MS/MS, LC/MS/MS

11 QuEChERS Acetonitrile Extraction Easy-to-use Covers broad range of analytes (less polar to highly polar) Suitable for high moisture samples (fruits and vegetables) Low costs and fast response Compatible with LC/MS and GC/MS But Limited clean-up (only dspe) Not suitable for fatty food Acetonitrile causes problems during GC analysis Anastassiades et al. (2003) J.AOAC Int, 86:

12 QuEChERS Challenges High matrix content Number of interferences present Need for more selective determination (UHP)LC-MS/MS (Ion trap, tandem MS) Accurate mass and high resolution MS 12 12

13 UHPLC/MS/MS in Pesticide Analysis Nowadays most often used approach due to: Selectivity Low detection limits achieved Speed Robustness But Target compounds only Limited number of transitions ( compounds/run) Transition set-up difficult GC compounds to be analyzed separately 13 13

14 SRM Compound Specific Optimization Goal: Maximize ion transmission into collision cell Choose optimal product ion Choose optimal collision energy OR 14 14

15 SRM Built in Databases in TraceFinder SRM already optimized and built into SW Select compounds to be analyzed from Datastore 15 15

16 Timed-SRM Maximize Dwell Time Min. Naphthol,1- Methomyl Fenuron o-phenylphenol_neg* Acephate Fuberidazole Propamocarb Tricyclazole CARBENDAZIM isoprocarb* Cymoxanil Cycluron Pyrimethanil thiabendazole Carbaryl Isoproturon Aldicarb_Sulfoxide* Promecarb Aldicarb+NH4 Aminocarb* Propoxur* Acibenzolar-S-methyl* Chlortoluron omethoate Simetryne monolinuron* Metribuzin* Pyracarbolid Thiofanox* Thidiazuron Bufencarb Methabenzhiazuron Carbofuran acetamiprid Butoxycarboxin Mexacarbate Monocrotophos Dioxacarb* Mepanipyrim Bendiocarb Mevinphos Methiocarb

17 Polar Pesticides in Food Extracts Polar pesticides dilution of QuEChERS extract necessary before injection to achieve good peak shape Acephate in acetonitrile Acephate in acetonitrile-h 2 O 17

18 Non-Polar Pesticides in Fatty-Food Extracts QuEChERS not applicable poor recoveries of non-polar compounds Gel Permeation Chromatography (GPC) clean-up Lehotay et al. (2005) JAOAC Int. 88:

19 Non-Polar Pesticides in Animal Tissues cyclohexane-ethyl acetate (1:1) extraction Anhydrous Na2SO4 GPC clean-up cyclohexane-ethyl acetate (1:1) Bio-Beads SX3 packing GC/MS and LC/MS/MS determination > 400 pesticides within % recovery (< 28% RSDs) Pang et al., (2006) J. Chromatogr. A, 1125 :

20 Why Use GC for Pesticide Aanalysis? Many compounds not amenable to LC separation Low polarity - poor atmospheric pressure ionization Difficult separation on LC columns Not extracted by QuEChERS from fatty food GPC needed GC offers many advantages Good separation efficiency Choice of detectors Easy coupling with MS 20

21 Traditional GC Approaches? GC with selective detectors: ECD, NPD, FPD still used for screening purposes Easy-to-use But cannot provide unambiguous confirmation GC/MS Robust Easy-to-use Spectral confirmation Lack of selectivity in some cases Not enough confirmation data points in difficult matrices 21

22 Problems with GC/MS Analysis of QuEChERS Extracts No concentration, final extracts <1.0 g/ml - lack of sensitivity Final extracts are in acetonitrile - problematic for GC analysis Limited injection volume due to high expansion coefficient of acetonitrile Consider (i) solvent exchange or (ii) PTV But: Solvent exchange requires care to avoid losses of volatile or unstable pesticides Repeated injection of large volumes of extracts can lead to column degradation and contamination of MS detector Limit of detection not sufficient for some analytes 22

23 Triple Quadrupole GC- MS/MS Workhorse in a Pesticide Residue Analysis Benefits of a triple quadrupole MS/MS Selectivity (Selected Reaction Monitoring) Lower detection limits Speed of analysis High number of analytes (up to 1500 in 1 run) Matrix elimination Robustness Method workflow benefits: Less sample clean-up Faster response Lower costs (labour, solvents, consumables, waste disposal) 23

24 Comparison of MS-SIM and MS/MS RT: Relative Abundance Relative Abundance Relative Abundance Relative Abundance Relative Abundance DSQIISIM Mode RT: NL: 6.37E4 m/z= F: + c SIM ms [ , , ] MS probe20f_sim RT: Time (min) TSQ Quantum GC Quinoxyfen in Hops MS/MS (SRM Mode) RT: RT: RT: NL: 2.67E4 m/z= F: + c SIM ms [ , , ] MS probe20f_sim NL: 9.94E3 m/z= F: + c SIM ms [ , , ] MS probe20f_sim NL: 6.10E5 m/z= F: + c EI SRM ms [ ] MS Genesis Probe20F NL: 1.06E6 m/z= F: + c EI SRM ms [ ] MS Genesis Probe20F 24

25 Excellent Detection in Difficult Matrices - Jam TSQ Quantum XLS: 1 µl injection of QuECheRS extract C:\Xcalibur\data\PRC jam\48275\ /23/ :47:46 STD IS RT TEST RT: SM: 9G RT: SM: 13G NL: 4.02E2 m/z= F: + c EI SRM ms NL: 1.66E4 m/z= F: + c EI SRM ms [ , ] MS [ ] MS NL: 3.21E m/z= Relative Abundance F: + c EI SRM ms [ ] MS NL: 4.06E3 m/z= F: + c EI SRM ms [ , ] MS Relative Abundance Time (min) Time (min) captan cyfluthrin SRM chromatograms for fruit preserve sample spiked at mg/kg 25

26 Comparing MS-SIM and MS/MS (SRM) for Cyfluthrin Abundance Time--> Abundance Ion ( to ): D Fruit jam sample spiked at mg/kg SIM* SRM** 1300 Ion ( to ): D Time--> *Based on acetone extraction followed by LLE and HPGPC **QuEChERS 26

27 Validation Results for GC Troublesome Compounds Pesticide 0.01 mg/kg 0.05 mg/kg mean CV mean CV captan* chlorothalonil dichlofluanid dicofol** dieldrin folpet iprodione tolylfluanid QuEChERS extraction 1 µl SL injection Excellent results *captan spike levels 0.02/0.10 mg/kg **dicofol spike levels 0.05/0.25 mg/kg 27

28 Further Options for Performance Improvement Inlet backflushing Efficient removal of non-volatiles Longer column lifetime Less frequent inlet maintenance Lower running costs and higher system uptime Highly Selective Reaction Monitoring Improvement of detection limits in difficult matrices 28

29 Use of Mass Spectrometry in Screening Analysis Simple sample preparation: QuEChERS, extract-n-shoot Target screening Single and Triple quadrupoles (SIM, SRM) Ion traps TOFs, Q-TOFs Non-target screening Single and Triple quadrupoles (SCAN) Ion traps (SCAN, Auto MS/MS) TOFs, Q-TOFs (accurate mass) 29

30 Exactive LC-MS unique tool in pesticide analysis Ultra-high resolution for separation of matrix from analytes Excellent mass accuracy for high confidence screening Quantitative capabilities Mass axis stability without lock mass calibration - robustness UHPLC compatibility No compound specific set-up ease-of-use 30

31 Exactive Residue Screening Strategy: QuEChERS extraction UHPLC/Exactive analysis Quantification: Xcalibur, LCQuan Target screening: ToxID Unknown screening: Sieve 31

32 Quantification Problems With Low Resolution Relative Abundance ppm 10 ppm 50 ppm 100 ppm Time (min) Relative Abundance Time (min) Relative Abundance Time (min) Relative Abundance Time (min) NL: 1.85E5 NL: 1.70E5 R=100k 100,000 R=10k 10,000 Imazalil, 25 ng/g in feed 32 32

33 High Resolution Benefits Detection Improvement R= 10,000 Acephate in spinach extract, 1 ng/g Poor peak shape at low resolutions R= 10,000 Clofentezine in spinach extract, 1 ng/g Not detected at low resolutions R= 100,000 R= 100,

34 Quantification Too! Excellent linearity in routine work 34 34

35 UHPLC Compatibility FWHM FWHM Enough data points even at FWHM resolution with common UHPLC peak widths 35 35

36 Compliance with Regulations Identification Criteria Identification point system: Decision 2002/657/EC Now accurate mass criteria added 2 ions < 5 ppm mass accuracy > Resolution FWHM SANCO/10684/2009: METHOD VALIDATION AND QUALITY CONTROL PROCEDURES FOR PESTICIDE RESIDUES ANALYSIS IN FOOD AND FEED 36 36

37 Conclusions Multi-residue methods are a must - saves time and cost to combine but some compounds are not suited - special methods needed. Pesticide properties and the matrix-type requires different extraction & sample prep. methods Pesticide type dictates whether GC or LC but important to separate matrix co-extractives from the analytes. MS/MS & high resolution MS increase multi-residue method success - ability to collect data for non-target compounds at the same time as acquisition for target compounds 37 37

38 A Global Perspective Food Safety Methods & Technologies 2010 COFFEE BREAK