33
switching is illustrated in data presented in Figure 3. Consistent ion ratios were achieved regardless of residue level for confirmation of positive findings.
The method and approach should be future proof in order to cope with most analytical challenges but modifications could be made to solve particular problems and to ensure that data remains SANTE compliant even when analysing very difficult matrices.
The instrument’s fast electronics means that more MRM transitions could easily be incorporated into the acquisition methods without sacrificing the integrity of the data. An additional 9 pesticides were added to method B for 2017 work using the same LC conditions without any compromise in performance. The high sensitivity of the instrument would allow significant dilution of the QuEChERS extracts to ensure that ‘dirty’ matrices would not foul the mass spectrometer.
The linear ion trap was not used in any of the work presented here but this additional functionality already included within the system could be utilised to enhance the method in the future. The QTRAP allows the use of Data Independent Acquisition (DIA) to collect additional MS/MS enhanced product ion (EPI) scans for additional identification. EPI spectra are highly selective and very sensitive due to accumulation of ions in the trap.
Highly selective and sensitive quantitation using MS/MS/MS is another option using the QTRAP, not as part of a routine workflow, but as a tool to solve a particular problem such as matrix interference affecting ion ratios. This is only an option if suitable fragments with enough sensitivity can be obtained.
Conclusions
Implementation of this method has had an extremely positive impact on workflow. Quantitative LC/MSMS data are acquired for hundreds of pesticides in 2 x 17 minute runs with repeat runs required only if positive findings exceed the calibration range. Less than 10 minutes per week are spent on instrument cleaning. Significant time has been saved on data processing due to the excellent signal to noise. The method/ system has the capacity for modifications to address future challenges that may be encountered in pesticide residue analysis.
References
1. Regulation (EC) No 396/2005 of the European Parliament and of the Council of 23 February 2005 on maximum residue levels of pesticides in or on food and feed of plant and animal origin.
Figure 3: Performance Data (100 injections over 28 hours run time using full acquisition method described above).
2. Commission Implementing Regulation (EU) 2017/660 of 6 April 2017 concerning a coordinated multiannual control programme of the Union for 2018, 2019 and 2020 to ensure compliance with maximum residue levels of pesticides and to assess the consumer exposure to pesticide residues in and on food of plant and animal origin
3. Anastassiades M, Lehotay SJ, Stajnbaher D and Schenck FJ, JAOAC Int 86(2) (2003) 412-31
4. European Commission. SANTE/11813/2017 21 –22 November 2017 rev.0.
Guidance document on analytical quality control and method validation procedures for pesticide residues and analysis in food and feed.
5. BS EN 15662:2008. Foods of plant origin. Determination of pesticide residues using GC-MS and/or LC-MS/MS following acetonitrile extraction/partitioning and clean- up by dispersive SPE. QuEChERS-method
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