Rapid and sensitive on-line solid phase extraction-ultra high performance liquid chromatography-electrospray-tandem mass spectrometry analysis of pesticides in surface waters

A simple, fast and sensitive method has been developed for the determination of 37 LC-amenable pesticides in surface water samples. On-line solid phase extraction (SPE) coupled to ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS. was employed for pre-concentration and analysis of all compounds in 16 min. SPE parameters were evaluated in order to increase sample throughput and detectability. Thus, injected sample volume, sample loading flow, carryover effects and reusability of the cartridges employed were studied, observing that 70 extractions can be performed with the same cartridge. Validation parameters were performed and good linearity (R2 > 0.99 in all cases) and precision (interday relative standard deviation values were lower than 14%) were obtained. Limits of detection (LOD) and limits of quantification (LOQ) were lower than 6.0 and 18.0 ng L−1 applying an injection sample volume of 1.5 mL, respectively, with exception of thifensulfuron methyl, whose limits were 10.0 and 33.0 ng L−1, respectively. On-line SPE recoveries were evaluated for three concentration levels (0.01, 0.03, 0.10 and 0.20 μg L−1) and acceptable values were found. The on-line SPE method was also compared with off-line SPE. Matrix effects were observed for majority of compounds and standard addition method was selected for analysis of real water samples. Finally, surface water samples were analyzed and, in all cases, the pesticide concentrations were below than the allowable limit in water for human consumption.