Monitoring of pesticides in river water using fully automated on-line solid-phase extraction and liquid chromatography with diode array detection with a novel filtration device

A modification of the SAMOS (System for the Automated Monitoring of Organic pollutants in Surface water) has been performed, which includes the attachment of four refrigerated flasks prior to the preconcentration unit, which act as sample reservoirs. River water is driven to the SAMOS, where it is pumped inside the flasks and afterwards it is preconcentrated onto C-18 precolumns of the Prospekt (Spark Holland, Netherlands), which is coupled on-line with liquid chromatography using the HP1090 equipped with a diode array detector (Hewlett Packard, Waldbron, Germany). The system is programmed in such a way that eight samples are analyzed on each day and it can be operated unattended for at least five days. In order to prevent clogging of the equipment due to the presence of particulate matter, a novel filtering device, comprising a 50-cm stainless steel cylindrical tube with 10 mu m pores, connected to a 190-mm diameter glass fiber filter with 1 mu m pores was installed. This configuration permitted satisfactory performance, with the unattended monitoring of Llobregat river water and with limits of detection (LODs) of 30-100 ng/l. Terbuthylazine was detected in Llobregat river effluent at a concentration of 13 mu g/l. Confirmatory analyses were performed by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry. This latter technique was also used to screen organophosphorus pesticides in the Llobregat river. (C) 1998 Elsevier Science B.V.