The analysis of pesticides & related compounds using mass spectrometry

The determination of pesticides and related materials in food and environmental samples is important and presents an enduring challenge to analytical chemists. For practicality it is important that as many pesticides as possible are compared using a common technique. Mass spectrometry is the method of choice for multi-residue detection techniques, because of its sensitivity and specificity. This thesis comprises a detailed analysis and critical review of the mass spectrometric behaviour of over 600 commonly encountered pesticides and related compounds. The work described in this thesis was undertaken in two tranches, one old and one new. The former experimental work was performed during the author’s employment at the Ministry of Agriculture, Fisheries & Food (Harpenden, Hertfordshire, UK) and at Unilever Research (Colworth House, Sharnbrook, Bedfordshire, UK). The data helped underpin the analytical work of the UK national pesticide residues monitoring surveillance team and the pesticide formulations safety team. Qualitative and quantitative aspects were both important, e.g. for identification and characterisation of active ingredients, contaminants and degradation products in technical pesticide formulations, as well as unambiguous detection and/or confirmation of residue levels in UK fruit and vegetables. The latter experimental work was undertaken recently (2015) at the Cardiff School of Chemistry during the preparation of this thesis. The newly acquired data helped confirm the validity and robustness of the original data, and helped to better understand them. Understanding the complex and sometimes unexpected behaviour of molecules during their extraction/analysis is essential, especially when performing trace analysis at the parts per billion level. Rationalisation of the mass spectrometric fragmentation pathways of these compounds was undertaken in order to better understand the fundamental processes taking place in the mass spectrometer. This improved understanding was essential in order to ensure the quality and validity of the data generated using these techniques. For comparison, some additional data are included, e.g. for chemical warfare agents, using literature data. Mass spectrometry was chosen because of its power as an analytical technique. General approaches and specific precautions which should be taken when using mass spectrometry for pesticide analysis are discussed and explained in this document and literature data were critically reviewed. It is hoped that these data and recommendations will find continued and future use as an adjunct to the plethora of literature data and MS instrument manufacturer databases