Transformation studies of some polar pesticides in water by on-line solid-phase extraction and liquid chromatography/particle beam-mass spectrometry

An on-line automated method for phototransformation studies of alachlor, aldicarb, and methiocarb by means of liquid chromatography/mass spectrometry (LC/MS) with particle beam (PB) interface is described. Surface water samples were first spiked with 50 mu g/l of each pesticide and then exposed to the radiation of a medium-pressure mercury lamp. Next, in regular intervals of 60 min, aliquots of 50-ml sample were enriched on a solid-phase extraction (SPE) cartridge and on-line eluted by a gradient of LC eluent onto analytical column for separation, followed by MS detection. A phototransformation experiment with each pesticide was performed twice, with MS operated in electron ionisation (EI) and positive chemical ionisation (PCI) modes. Many transformation products (TPs) of parent pesticides were detected and in numerous instances, tentatively identified. Appearance of several transformation products is reported for the first time.