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Abstract No.: MoP-LB2
Session: LATE-BREAKING/Food and Nutrition
Presentation date: Mon, Aug 28, 2006
Presentation time: 14:30 – 16:00

Method Development for the Analysis of Pesticide Residues in High Fat Content Foodstuffs

Petra Kopecka1,2, Matthew J. Almond1, Jas Oliver-Kang2

1 The University of Reading, Reading, United Kingdom
2 CEM Analytical Services, North Ascot, United Kingdom

Correspondence address: Petra Kopecka, The University of Reading, School of Chemistry, Whiteknights, Reading, RG6 6AD United Kingdom.

Keywords: Chromatography, Gas; Mass Spectrometry; Matrix Effects; Pesticides.

Novel aspect: Pesticide residue analysis in high fat content matrices.

 

Currently more than 800 pesticides are used worldwide. Thus, various pesticides may be present in food products, many at very low concentrations. Most persistent pesticides are lipophilic compounds, therefore monitoring their levels in high fat content foodstuffs is a major concern. For screening of these foodstuffs, multi-residue analytical aproaches are necessary to reduce the analytical workload.

A multi-residue method is being developed for the analysis by GC-MS and HPLC-MS of a wide range of pesticide residues at low concentrations (LOQ at 10 ppb) in high fat content foodstuffs.
The presented work focuses on the technique of GC-MS. A mixture of 48 pesticides was prepared (including aldrin, endrin, dieldrin, the DDT group, the HCH group, chlordane, heptachlor, etc.) over a concentration range from 10 to 10 000 ng/mL. Preliminary experiments have centred upon determining the optimum experimental and instrumental parameters for GC-MS analysis of this pesticide mixture. Parameters studied include: optimisation of resolution, SIM quantitation and testing the influence of the solvent and the optimised GC-MS parameters will be presented.
The crucial stage in this work is to develop sufficient extraction and clean-up procedures prior to sample analysis to overcome the strong influence of the high fat content in the matrices.
Initial results, presented in the poster, demonstrate that fatty matrices have a very strong influence on the detection of target analytes. The creation of ions via fragmentation is strongly affected, i.e. enhanced or repressed, according to the chemical environment of the analytes. Moreover, ions of analytes interact with ions of the matrix, and/or in the presence of the matrix the analyte ions are often not stable enough to be detected. Furthermore, the analyte responses may be obscured by overlapping matrix peaks, or other analyte responses may be enhanced significantly because of the presence of the matrix. This confirms the need for an efficient clean-up procedure.
The results from experiments utilising Florisil as a clean-up step are encouraging, since introducing a Florisil column allowed the detection of significantly more compounds in the pesticide mixture (34 in total), compared to a sample pre-treatment procedure without any purification step. Further optimisation of the extraction and clean-up steps is the main objective of this study.

Acknowledgement
This study has been funded by CEM Analytical Services (CEMAS) and the Knowledge Transfer Partnership of the UK Department of Trade and Industry.