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Screening for Hundreds of Pesticides in Fruits and Vegetables using the Agilent 7200 GC/Q-TOF with a new Exact Mass Pesticide Library
Philip L. Wylie, Ph.D.
Agilent Technologies
Wilmington, DE
March 2, 2015
ASMS
1
7200 Quadrupole Time of Flight
What Can the GC/Q-TOF Do?
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TOF mode (full spectrum acquisition) • High resolution full spectral acquisition • Accurate mass measurements • Fast acquisition of full spectra
Q-TOF mode (MS/MS) • Full spectrum of Product Ions (SIM-TOF)
- With high resolution and accurate mass
• Selectivity beyond any “triple quad” MRM method - Confirm TOF spectrum without interferences
• High sensitivity structural elucidation tool
Ideal tool for solving complex analytical problems
7200B Performance Specifications
Resolving Power: >12.5K at m/z 272 • 13K to 15K typical
Mass Accuracy: <3 ppm for 7200B • <2 ppm typical
MS Sensitivity <250 fg of OFN derived statistically
Dynamic Range: > 3 orders of magnitude • 4 orders with Dual Gain
TOF Mass range: 20-3000 u
MS/MS Mass range: 20-1050 u
Spectral Rate: 1-50 Spectra/sec
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Internal Reference Mass (IRM) Compound
1,3,5-Triazine, 2,4,6-tris(pentafluoroethyl)-, [C9F15N3]*+ = 434.9847
Accurate mass EI spectrum [M]+ = 434.9847 Measured mass Accurate Mass Mass Accuracy ppm
434.9839 434.9847 -1.8391
434.9839
Tune TOF Mass Axis as Part of a Sequence
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In sequence table: - Choose “Keyword” for Type - Choose “MassCal” for Keyword Mass calibration takes only 90 seconds
I usually do not use the Internal Reference Mass because it is not needed.
Camphor Accurate Mass – Internal Reference Mass (IRM) Turned Off
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Measured M*+ =
152.1197
Calculated M*+ = 152.1196 Difference = 0.88 ppm
Where is the GC/Q-TOF being used?
Natural Products
Metabolomics
Food Safety and Testing
Flavor and Fragrances
Forensics and Toxicology
Environmental
Energy and Petrochemical
Screening Pesticides with a GC-Q/TOF
• Accurate Mass provides added compound selectivity - Higher resolution provides added interference selectivity • TOF mode : Always full spectral data, Non-targeted acquisition • ‘Unlimited’ number of compounds can be screened (search
accurate mass compound database for identification) • Sensitivity is the same regardless of number of compounds
screened • MS/MS (Q/TOF Mode) further assists compound
identification
Pesticide screening GC-Q/TOF
About 300 pesticides listed with names beginning with “C”
Enhanced Selectivity using Accurate Mass
March 2, 2015 11
Full Scale
200,000,000
200,000
5000
230.9737 +/- 10 ppm
383.9871 +/- 10 ppm
Ethion @ 5 ppb in Ginseng Extract Extracted Ions = 230.9737 and 383.9871 +/- 10 ppm
PCDL : Personal Compound Database & Library with ~750 Pesticides
• Name • Mol. Formula • Mono-isotopic exact mass • Locked RT • CAS # • Exact mass spectrum
All Ions data processing - Method setup (1) Formula Source
Pesticide screening GC-Q/TOF
• All Ions always uses RT
• Specify PCDL
All Ions data processing - Method setup (2) Formula matching
Pesticide screening GC-Q/TOF
• Set mass window for fragment EICs
All Ions data processing - Method setup (3) Fragment Identification
Pesticide screening GC-Q/TOF
• Select minimum number of qualified fragments required to identify compound
• Co-elution score is the major function to qualify compounds based on similarity of extracted ion peak shapes & RTs
• Select number of fragment ions to be evaluated
Vinclozolin: 10 ppb in Catfish Extract
Vinclozolin: 10 ppb in Catfish Extract
Target Compound List And Results
1 2
3 4
5
Compound Identification Results
Extracted Ion Chromatograms
Coelution Plot
Molecular Ion / Isotope Ratio Results
Spectrum & Extracted Ion Plots
Vinclozolin 10 ppb: EICs and Coelution Plot
Fenpropathrin in Catfish: Is it really there?
Fenpropathrin in Catfish Extract: M+* Isotope Ratios are not Perfect
Fenpropathrin in Catfish Extract: Retention Time and Mass Accuracy are Very Good
Δ RT = 0.008 min Mass Accuracy = 2.45 ppm
Hexachlorobenzene 10 ppb in Catfish Extract
Kadethrin: Review shows that this is a false Positive
Library Spectrum
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
March 2, 2015
ASMS
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Backflush, RTL GC Methods Employed 40 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
100 108
Inlet
MS
Aux
Column #1 15m
Column #2 15m
PCT
Mid-point Back flush Inlet
MS
Aux
Column #1 5m
Column #2 15m
PCT
‘Mid’-point Back flush
Matrix
Ave.
% Identified
(5X15) Of 108 Pest.
95.4 86.1 90.7 96.3 90.7 93.5 92.1
% Identified
(15X15) of 100 Pest.
96 91 94 98 89 94 93.7
Pesticides Identified at 10 ng/mL Spiking Level
Matrix
Ave.
% Identified
(5X15) Of 108 Pest.
100 100 96.3 99.1 98.1 96.3 98.3
% Identified
(15X15) of 100 Pest.
100 99 97 100 100 98 99
Pesticides Identified at 100 ng/mL Spiking Level
Mass Accuracy in Matrix– A function of S/N
Measured S/N Average difference between Exact Mass and Measured Mass (ppm)
< 10 6.7
> 10 < 100 1.8
> 100 1.2
Broccoli extract spiked at 100 ng/mL
Pesticide Screening by GC/Q-TOF Summary
Pesticide screening GC-Q/TOF
• Continuing trend towards comprehensive pesticide screening methods using accurate mass instruments
• Innovative data mining tools for identification of trace contaminants in complex matrices
• All Ions integrated workflow for enhanced qualification of suspected compounds by additional fragment ions in qualitative screening
- Similar Workflow as on LC- QTOF • Easy customizable and generation of user PCDL Libraries • Personal compound database library contains > 700 pesticides
with GC/MS accurate mass MS spectra and locked retention times
• Seamless integration of compound identification and MH Quantitation for easy and quick batch review
