Automated sample preparation with extraction columns by means of anti-isoproturon immunosorbents for the determination of phenylurea herbicides in water followed by liquid chromatography–diode array detection and liquid chromatography–atmospheric pressure chemical ionization mass spectrometry

Abstract

The retention of five phenylurea herbicides (chlorotoluron, isoproturon, diuron, linuron and diflubenzuron) was evaluated by solid-phase extraction with an automated sample preparation (ASPEC) system using anti-isoproturon immunosorbents. The extraction was carried out after the percolation of 50 ml of LC-grade water and groundwater samples spiked with a mixture of the five pesticides at the ppb level and then elution with 4 ml of a mixture of methanol–water (70:30, v/v) and 1 ml of LC-grade water. The recoveries obtained ranged from 16 to 97% indicating a good affinity of the polyclonal antibodies of the immunosorbent for compounds with similar structures to the antigen pesticide isoproturon. An inter-laboratory study using Aquacheck certified samples was performed in order to validate the use of the immunosorbent for the analysis of environmental water samples. For the groundwater samples the calibration curves were linear in the range between 1 and 3 μg/l for each compound using liquid chromatography with diode array detection (LC–DAD). The overall mean difference comparing the values obtained by this method and the real values given by Aquacheck varied between 1 and 22%. All samples were analyzed simultaneously by LC–DAD and liquid chromatography–atmospheric pressure chemical ionization mass spectrometry.