Target and Non-target Pesticide Residue Analysis Using GC/QQQ and GC/Q-TOF with a Discussion on Ways to Use Sandwich Injections

Transcription

1 Target and Non-target Pesticide Residue Analysis Using GC/QQQ and GC/Q-TOF with a Discussion on Ways to Use Sandwich Injections Philip L. Wylie Agilent Technologies Wilmington, DE 1

2 Topics Target vs. Non-target vs Comprehensive Pesticide Analysis 10X more sensitive GC/QQQ Agilent 7010 GC/Q-TOF as a screening tool for >740 pesticides Sandwich injections make life easier & chromatography better 2

3 Target and Non-target Pesticide Analysis Target Compounds are known Have mass spectra or MRMs Have a defined list of compounds You know what you are looking for You will only find what you are looking for Typically look for pesticides True Non-target It could be anything May not be in any library May need multiple tools to identify it Sort of Non-target or Comprehensive Screening It could be any pesticide It is in a library or PCDL You cast a much wider net May find pesticides you didn t expect to see Screen for virtually all GC-able pesticides (>740) 3

4 GC/MS tools for target and non-target pesticide residue analysis Target Non-target 7010 GC/QQQ (or GC/MS SIM) 7200 GC/Q-TOF (or GC/MS Scan) 4

5 GC/QQQ Electron Ionization has gotten much more sensitive with introduction of the 7010! 500 attograms of OFN 5

6 Dioxins 2,3,7,8-TCDD at 5 fg Level 2,3,7,8-TCDD 10 fg on column 5 fg/µl; 2 ul injected Courtesy of Jessica Westland, Agilent Technologies 6

7 Taking advantage of 10X increase in GC/QQQ sensitivity Reduce sample amount for extraction - Use less solvent and QuEChERS reagents Save $ Reduce injection volume - Liners last longer Save time and $ - Column stays cleaner Better chromatography - Source stays cleaner More up time Shorter dwell times & still more sensitive - More analytes in the method More comprehensive - More MRMs per compound More confidence in hits 7

8 Recoveries for 126 Difficult Pesticides Spiked into Carrot, Tomato & Celery at 1, 5, 10 & 50 ng/g Reduced QuEChERS extraction from 15 g to 2 g Reduced injection volume from 2 µl to 0.5 µl Melissa Churley and Joan Stevens, ASMS 2015 Poster WP 060 8

9 64 Injections of a QuEChERS Extract of an Apple Comparing 2 µl to 0.5 µl Injections 2 µl 0.5 µl 9

10 Build a Pesticide MRM Method in Minutes from the Pesticides & Environmental Pollutants Database >1000 compounds Average of 8 MRMs/compound $70,000 of standards purchased 10

11 But, why do we also need to screen? About 300 pesticides listed with names beginning with C

12 Comprehensive Pesticide Screening is Needed along with Target Analysis Screen for >740 GC-able pesticides by GC/Q-TOF in TOF Mode Add any hits to the GC/QQQ target method 12

13 Enhanced Selectivity using Accurate Mass 5 ppb in Ginseng Extract Extracted Ions = and /- 10 ppm Full Scale 200,000, , /- 10 ppm /- 10 ppm 13

14 PCDL : Personal Compound Database & Library with ~740 Pesticides Name Mol. Formula Mono-isotopic exact mass Locked RT CAS # Exact mass spectrum

15 All Ions data processing - Method setup Specify PCDL Lock your acquisition method to the RTs in the PCDL Choose mass extraction window size Choose the number of significant ions to extract Choose the minimum number of Qualified ions for a hit Pesticide screening GC-Q/TOF

16 Vinclozolin: 10 ppb in Catfish Extract

17 Vinclozolin: 10 ppb in Catfish Extract Target Compound List And Results Compound Identification Results Extracted Ion Chromatograms Molecular Ion / Isotope Ratio Results Coelution Plot Spectrum & Extracted Ion Plots

18 Analysis of spiked fruits and vegetables Use organically grown produce EN QuEChERS extraction 2 spiking levels 10 ppb and 100 ppb Compare two different GC methods 20 min vs 40 min Optimize All Ions setpoints See how many pesticides can be found Measure TOF mass accuracy 18

19 Backflush, RTL GC Methods Employed 40.5 Minute Constant Flow Method 20 Minute Constant Flow Method Columns 2 x 15m 5m + 15m Back flush type Mid-point Mid -point # Spiked Pesticides in PCDL Inlet Mid-point Back flush Aux Inlet Mid -point Back flush Aux Column #1 15m Column #2 15m Column #1 5m Column #2 15m PCT MS PCT MS

20 Chromatograms of QuEChERS Extracts

21 MassHunter Qual Showing Compound Details View: Results for Quinoxyfen at 10 ng/ml in Green Bean Extract a) b) c) e) d) f) 21

22 Quinoxyfen at 10 ng/ml in Green Bean Extract Extracted ion chromatograms Coelution plot Compound identification results 22

23 Quinoxyfen at 10 ng/ml in Green Bean Extract: Molecular ion isotope pattern Red rectangles show theoretical abundance and spacing Extracted exact mass ions of M *+ TIC in M *+ range 23

24 Pesticides Identified at 10 ng/ml Spiking Level Matrix Ave. % Identified (5X15) Of 93 Pest. % Identified (15X15) of 86 Pest % %

25 Pesticides Identified at 100 ng/ml Spiking Level Matrix Ave. % Identified (5X15) Of 93 Pest. % Identified (15X15) of 86 Pest % %

26 Sandwich Injections 2-layer or 3-layer 26

27 Analyte Protectants in a Sandwich Injection ethylglycerol *sorbitol *gulonolactone shikimic acid Examples of Analyte Protectants *APs used in the following experiments

28 Ratio of peak heights for 17 pesticides when APs are on bottom compared to APs on top layer 2.00 Ratio Bottom:Top Ratio Bottom:Top

29 Ratio of APs on bottom to APs on Top (blue) Ratio of APs on bottom to no APs injected (yellow) Ratio Bottom:Top Ratio Bottom:No APs

30 Atrazine APs on bottom APs on top No APs

31 Conclusions Target and comprehensive screening methods are needed for pesticide residue analysis Target analysis is usually done by GC/QQQ New GC/QQQ is 10X more sensitive Attogram level detection (for some compounds) New Screening approach uses GC/Q-TOF with exact mass PCDL with >740 GC-able pesticides >97% of spiked pesticides were found at 10 ppb level in spiked produce (>99% at 100 ppb) Sandwich injections: an easy way to add analyte protectants (and/or matrix and/or internal standards) 31

32 Acknowledgements Agilent Colleagues Joni Stevens Sophia Nieto Kai Chen Melissa Churley Jessica Westland 32

33 Portrait with Vegetables (The Greengrocer) Artist: Giuseppe Arcimboldo b d. 1593, Milan, Italy Thank You