Monitoring of pesticides in river water based on samples previously stored in polymeric cartridges followed by on-line solid-phase extraction-liquid chromatography–diode array detection and confirmation by atmospheric pressure chemical ionization mass spe

Solid-phase extraction coupled on-line with liquid chromatography–diode array detection was applied to the monitoring study of a group of pesticides and metabolites of different chemical groups in water samples from the Ebro delta area (Tarragona, Spain). Liquid chromatography–atmospheric pressure chemical ionisation-mass spectrometry was used for confirmatory purposes. The developed method involves the preconcentration of 50 ml of water samples through styrene–divinylbenzene precolumns. The most frequently detected pesticides in the analysed samples were bentazone, molinate, metolachlor and the triazine herbicides simazine, atrazine and its dealkylated metabolites, deisopropilatrazine and deethylatrazine and, at concentration levels ranging from 0.03 to 2.4 μg l−1. The stability of several pesticides stored on styrene–divinylbenzene cartridges was also evaluated. The effect of different storage temperatures (room temperature, 4°C and −20°C) and two storage periods (one week and three months) on the recovery of the pesticides were considered. In general, the recoveries were greater than 90% after three months of storage at −20°C on the polymeric cartridges.