Page 24 - Application Notebook - Solution for Food Safety

LAAN-A-LM-E124

Application Liquid Chromatography Mass Spectrometry

News Applying ‘MRM Spectrum Mode’ and Library
Searching for Enhanced Reporting Confidence in
Routine Pesticide Residue Analysis
No. C154 David R. Baker , Chris Titman , Jonathan Horner , Neil Loftus 1
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Shimadzu Corporation, UK; Scientific Analysis Laboratories, UK

„ Abstract „ Introduction
To help reduce the incidence of false positive and false Multiple Reaction Monitoring (MRM) based LC-MS/MS
negative reporting in pesticide residue monitoring techniques are widely used on triple quadrupole
routine multiple-reaction monitoring (MRM) methods platforms for targeted quantitation as a result of high
have been enhanced to monitor a higher number of selectivity, sensitivity and robustness. In a regulated
fragment ion transitions to increase specificity and environment such as food safety there is a growing need
reporting confidence. In this workflow, typically 6-10 to enhance the capability in routine monitoring
fragment ion transitions were monitored for each programs by increasing the number of pesticides
target pesticide as opposed to a conventional measured in a single analysis and at the same time
approach using 2-3 fragment ions. By acquiring a high delivering the highest confidence in compound
number of fragment ion transitions, each target identification to reduce false detect reporting. For
pesticide had a corresponding fragmentation spectra pesticide analysis in the EU, identification criteria in
which could be used in routine library searching and SANTE/11945/2015 requires the retention time and the
compound verification using reference library match ion ratio from at least 2 MRM transitions to be within
*1
scores. This ‘MRM Spectrum Mode’ was applied to acceptable tolerance limits. However, even applying
quantify and identify 193 pesticides using 1,291 MRM this criteria it is well reported that false positives can
transitions without compromising limits of detection, occur in certain pesticide/commodity combinations. *2-*4
linearity or repeatability.
To reduce false negative and false positive reporting a

higher number of MRM transitions were used for each

target pesticide to increase the level of confidence in
assay specificity. The number of fragment ion
Compound Name Linuron transitions monitored for each target pesticide was
Formula C9H10Cl2N2O2
CAS 330-55-2 dependent upon the chemical structure with typically
between 6-10 fragment ions for each compound. MRM
Spectrum mode combines conventional MRM
quantitation with the generation of a high quality MRM
Conventional approach MRM Spectrum Mode
2 MRM’s 9 MRM’s product ion spectrum which can be used in routine
1:248.80>160.00 1:248.80>160.00 library searching and compound verification and
2:248.80>182.10 2:248.80>182.10 identification.
3:250.80>162.00

4:248.80>133.10
5:250.80>135.00 In this application paper we present the development
6:248.80>161.00 of a method for 193 pesticides, with 1,291 MRM
7:250.80>184.10 transitions, and a 15 minute cycle time. In order to
8:248.80>125.00 acquire this number of MRM transitions using a short
9:248.80>153.00
run time a 3 msec dwell time was applied to each MRM
Higher specificity transition and a 5 msec polarity switch was used. On
Higher reporting confidence average 7 MRM transitions were applied to each
Library searchable fragment compound. The method was quickly set up using the
data
Shimadzu Pesticide Method Package, a data base with
7.75 8.00 min 7.75 8.00 min more than 750 pesticides and over 6,000 MRM

transitions designed to accelerate method set-up and
Using a higher number of fragment ions in MRM data help compound verification. MRM Spectrum mode was
acquisition increases the specificity of detection and reduces
false negative and false positive reporting. In the case of also compared to a conventional pesticide monitoring
linuron, 9 precursor-fragment ion transitions were used to method with 2 MRMs per compound (386 MRMs in
increase confidence in assay specificity. There is no compromise total) in order to assess the effect on data quality when
in data quality between methods despite a higher number of adding additional MRM transitions to the method.
fragment ions monitored. Signal intensity, linearity, Several different food commodities were analysed with
reproducibility are in good agreement between both methods. varying complexity (turmeric, plum, peppermint,
parsnip, cherry, lime, pumpkin, tomato, potato). Data
was processed using LabSolutions Insight software
which provides automated library searching of target
MRM spectrum.