Determination of pesticides and chloroanisoles in water samples using gas chromatography-mass spectrometry.

Traditionally, pesticide residue analysis methods have focused on the analysis of a single pesticide or a group of chemically related pesticides, but this does not reflect the true varied distribution of residues within the environment. Initially, in this project multi-pesticide residue analysis methods were developed for capillary gas chromatographs using electron capture detection. Variation in temperature conditions, ramp rates and carrier gas flow rates were made to optimise both the resolution and speed of analysis for mixtures of carbaryl (a carbamate), lindane (an organochlorine), chlorpyrifos and chlorpyrifos-methyl (both organophosphorus compounds) and simazine (a triazine herbicide). These methods were then applied to the determination of pesticides spiked into surface and drinking water samples and the recoveries measured.The same procedure was applied to the chromatographic determination of chloroanisoles, which are believed to result from biotic O-methylation of phenols within the environment. Methods were optimised for the analysis of eleven out of the possible nineteen chloroanisoles available.Traditionally, such chromatography would have been preceded by solvent extraction of residues, followed by concentration of the resulting organic extract. These methods were compared with the use of the more recently developed Solid Phase Extraction (SPE) cartridges. These allow the extraction of organic materials from large volumes of aqueous samples onto a cartridge followed by subsequent elution using a second solvent. Preliminary work was done on SPE in order to find suitable solvent for both steps so that the analytes could be selectively retained and subsequently released from the cartridges.The next stage involved the extraction using SPE methods from water samples from rivers around Sheffield. Samples were spiked with a range of pesticides or chloroanisoles prior to extraction and the extracts analysed by gas chromatography-mass spectrometry. Recoveries were found to vary between compounds. Lindane, one of the pesticides used to spike the samples was found to be already present in samples taken from the River Rother at low part per billion levels. Possible sources for this finding are discussed. The presence of chloroanisoles which had previously been reported in this river was not observed.