Investigation of photochemical behavior of pesticides in a photolysis reactor coupled on-line with a liquid chromatography electrospray ionization tandem mass spectrometry system - Application to trace and confirmatory analyses in food samples

The photochemical behavior of pesticides in a photolysis reactor coupled on-line with a liquid chromatography-electrospray ionization mass spectrometer (LC-h nu-MS) was investigated. This paper describes the application of LC-h nu-MS, in combination with tandem mass spectrometry (MS-MS), to identification of phototransformation products and to the establishment of possible photolytic pathways of pesticides. In addition, the applicability of LC-h nu-MS as an alternative to LC-MS-MS, for trace and confirmatory multiresidue analysis in food samples was investigated. To demonstrate the potential of this technique, a series of N-heterocyclic compounds, phenylureas and carbamates, was studied. Several parameters, such as irradiation time and nature of photosensitizers, were investigated, and their impact on the photolytic transformation is presented here. The technique's versatility is also exhibited by using it for identification of triazine isomers, and for detection of pesticide residues in food sample extracts. Illustrative applications for analysis in lettuce and blueberry extracts are described. (C) 1998 Elsevier Science B.V.