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

Solid-phase extraction coupled on-line with liquid chromatography-diode arr ay detection was applied to the monitoring study of a group of pesticides a nd metabolites of different chemical groups in water samples from the Ebro delta area (Tarragona, Spain). Liquid chromatography-atmospheric pressure c hemical ionisation-mass spectrometry was used for confirmatory purposes. Th e developed method involves the preconcentration of 50 mi of water samples through styrene-divinylbenzene precolumns. The most frequently detected pes ticides in the analysed samples were bentazone, molinate, metolachlor and t he triazine herbicides simazine, atrazine and its dealkylated metabolites, deisopropilatrazine and deethylatrazine and, at concentration levels rangin g from 0.03 to 2.41 mu g l(-1). The stability of several pesticides stored on styrene-divinylbenzene cartri dges was also evaluated. The effect of different storage temperatures (room temperature, 4 degrees C and -20 degrees C) and two storage periods (one w eek and three months) on the recovery of the pesticides were considered. In general, the recoveries were greater than 90% after three months of storag e at -20 degrees C on the polymeric cartridges. (C) 1999 Elsevier Science B .V. All rights reserved.