Determination of pesticides and their degradation products in water samples by solid-phase extraction coupled with liquid chromatography-mass spectrometry

In this study, solid-phase extraction (SPE) of the pesticides, including ametryn, prometon, bentazon, carbendazim, tebuconazole, dimethoate and their degradation products, deisopropylatrazine and hydroxyatrazine, with high-performance liquid chromatography-tandem mass spectrometric analysis, was reported. The SPE approach consisted of the application of hydrophilic lipophilic-balanced polymer (HLB), strong cation, and anionic exchange sorbents packed in layered sequence in a single cartridge. The influence of various parameters on the extraction process was investigated, including sample solution pH, elution solvent, ionic strength and sample loading volume. Under the optimal conditions, the relative recoveries of the analytes ranged from 76 to 97% for spiked water and surface water samples with relative standard deviations of 1-9%. The method displayed low method detection limits for both water matrices (0.001-41.27 ng L-1) and achieved good linearity over the tested range of concentrations. Sequential-mode SPE provided higher extraction efficiency for pesticides than liquid-liquid extraction, and the adsorption capacity was greater than that of commercial HLB material, in the presence of humic acids. Eleven reservoir water samples were processed by the procedure, and tebuconazole was detected in all samples at concentrations of between 0.12 and 15.93 ng L-1, confirming that this mode of SPE was suitable for application to real samples.