A Novel Approach to the Reduction of False Positive and Negative Identifications in Screening of Pesticide Residues in Food Analysis

Transcription

1 A Novel Approach to the Reduction of False Positive and Negative Identifications in Screening of Pesticide Residues in Food Analysis M McCullagh, Severine Goscinny, Ramesh Rao and Vincent Hanot 2013 Waters Corporation 1

2 Overview Introduction Classification of screening Benefits of Tof screening CCS screening a new identification point Collision Cross Section screening software Routine screening using ion mobility Ion mobility spectral cleanup Protomer/isomer characterisation Summary 2013 Waters Corporation 2

3 Residue screening classification Targeted screening (QQQ) Well-defined target list of analytes Selective acquisition and/or processing modes Analytical standards available for every compound Non-targeted (suspect) screening (Tof) Non-targeted relates to the acquisition type Screen against a comprehensive library of known compounds Analytical standards available for most compounds Unknown screening (Tof) No defined target list Compound not present in the library, maybe a new chemical structure Structural elucidation required 2013 Waters Corporation 3

4 Key drivers for accurate mass screening? Ability to perform full spectral analysis Provides greater insight into the composition of a complex sample Increased specificity in complex matrices Accurate mass, diagnostic fragment ions Ability to perform non-targeted analysis The freedom to measure compounds without prior compound specific tuning Ability to screen for larger number of compounds and adducts Compared to QQQ based screening 2013 Waters Corporation 4

5 Detection results used to reduce false detects Pesticide Screening Library - Over 2000 compounds with structure, synonyms, and formulae. Over 600 of which have detection results False detection rates increase with increasing library size Critical information that is used for ID process Name (chemical, common, synonyms, marker residue definition) Chemical formula Structure Retention time Accurate mass precursor ions Accurate mass fragment ions Isotopic patterns Isotope intensity s 2013 Waters Corporation 5

6 2013 Waters Corporation 6

7 SYNAPT G2-S High Definition MS (HDMS) - instrument schematic 1. Increased sensitivity Orthogonal acceleration QToF 2. Ion mobility 3. Accurate mass measurement Size Shape Charge 2013 Waters Corporation 7

8 What is CCS? CCS is an important distinguishing characteristic of an ion which is related to: chemical structure 3-dimensional conformation CCS is a robust and precise physicochemical property of an ion Waters Corporation 8

9 Orthogonal mobility separation % Ion mobility orthogonal separation Mandarin 1000 ppb SynaptG2S_ WIVI_27MARCH2012_ SynaptG2S_ WIVI_27MARCH2012_165.raw : : TOF MS ES+ BPI 9.69e Time UPLC separation 2013 Waters Corporation 9

10 Ion Mobility Orthogonal Separation 2013 Waters Corporation 10

11 Boscalid in mandarin matrix B: Conventional background subtracted spectrum A: Conventional MS spectrum generated 2013 Waters Corporation 11

12 UPLC resolution of analytes and mandarin matrix components Resolution obtained for boscalid and matrix components 2013 Waters Corporation 12

13 Orthogonal mobility resolution of boscalid and mandarin matrix components Overlaid intensity versus mobility drift time plots 1. Boscalid 2. Matrix 3. Matrix Mobility resolved analyte and matrix components 2013 Waters Corporation 13

14 Single component mass spectra of analyte and mandarin matrix components Single component matrix spectrum Single component matrix spectrum Single component boscalid spectrum 2013 Waters Corporation 14

15 Boscalid: Matrix Dependent Retention Time Shifts Boscalid Expected Retention Time 7.35 mins (standard): Matrix Dependent Retention Time Shifts Matrix Rt (mins) %Error Pear Mandarin Leek Ginger Waters Corporation 15

16 Drift Time(mS) Impact of matrix on ion mobility drift time 7 Plot of Drift Time Vs Expected Mass for Pesticides in Different Matrices Mandarin Ginger Leek Pear Expected Mass (Da) 2013 Waters Corporation 16

17 % Drift time deviation Confidence in using ion mobility for screening 2.0 % Mean drift time deviation of four matrices against solvent standard control Imazalil Napropamide Pyrimethanil Pirimicarb Metribuzin Tetraconazole Cyproconazole II Oxadiazon Simazine Fenoxycarb Heptenophos Monolinuron Sulfosulfuron Flufenoxuron_1 Haloxyfop Propamocarb prosulfuron paraoxon methyl Triasulfuron Thiophanate-methyl Thiacloprid Pyriproxifen Pyraclostrobin Omethoate Nitenpyram Metolachlor Mesotrione Isoproturon Imidacloprid Fosthiazate Flutriafol Flutolanil Fluroxypyr Fenhexamid Diuron Dicrotophos Dichlorvos Cyprodinil Clethodim Chloridazon (Pyrazon) Chlorbromuron Boscalid Azoxystrobin Acetamiprid -2.5 Mean %deviation calculated from 4 matrices Pesticide p = Waters Corporation 17

18 New Ion Mobility Software UNIFI CCS Research Edition 2013 Waters Corporation 18

19 Multiple identification points: Intelligent software filtering Cast the net wide Intelligent software: Target identified 2013 Waters Corporation 19

20 Results summary for EU RL proficiency sample FV-13 8 Expected to be detected 29 Observed using a wide screen 2013 Waters Corporation 20

21 Results summary for EU RL proficiency sample FV-13 8 Expected to be detected False +ve False -ve 9 Observed after 10 ppm accurate mass and fragment filtering 2013 Waters Corporation 21

22 Results summary for EU RL proficiency sample FV-13 Ion mobility More SPECIFICITY More CONFIDENCE More EFFICIENCY False +ve removed False -ve avoided 8 observed after CCS filtering 2013 Waters Corporation 22

23 New Ion Mobility Software UNIFI CCS Research Edition 2013 Waters Corporation 23

24 Observed MS E spectra for spinosad in EU RL proficiency sample FV-13 Ion mobility resolution spectral clean up, more specificity 2013 Waters Corporation 24

25 Mobility resolved observed MS E spectra for spinosad in EU RL proficiency sample FV-13 Fragments are mobility aligned and retention time aligned Ion mobility resolution spectral clean up, more specificity 2013 Waters Corporation 25

26 New Ion Mobility Software UNIFI CCS Research Edition 2013 Waters Corporation 26

27 Observed residue indoxacarb with retention time aligned fragments One chromatographic peak Two fragments peaks M R M E Q U I V A L E N T 2013 Waters Corporation 27

28 Observed MS E spectra for indoxacarb in EU RL sample FV-13 Data processed to target two protomers Observed for 1 st time Only Possible With SYNAPT G2-S Ion mobility protomer resolution and even more specificity 2013 Waters Corporation 28

29 Observed MS E spectra comparison for indoxacarb protomers in EU RL sample FV Waters Corporation 29

30 Indoxacarb identification points A unique combination Providing a unique solution X 3 CCS Unique confidence and 2 efficiency fragmentation routes Unique with ion 2 mobility Protomers Retention time and drift time aligned Spectral clean up Accurate mass precursor and fragments 2013 Waters Corporation 30

31 Summary False positives can be removed and false negatives avoided using CCS values as a screening parameter. CCS can be used as a complimentary identification point. Mobility resolution facilitates spectral clean-up for both precursor and fragment spectra. CCS adds confidence in identification where retention time or mass shifts have been observed. Protomers not previously observed have been routinely identified and characterised Waters Corporation 31