Determination of chlorpyrifos in water used for agricultural production

Abstract

The quality of the water for irrigation in conventional, but especially in organic food production is very important. The presence of pesticide residues in water may cause yield reduction and decrease product quality, due to its uptake. Chlorpyrifos is one of the most widely used insecticide in the world and it ts detected in surface and groundwaters more frequently than any other organophosphorus insecticide. Also, chlorpyrifos is one of the most important water pollutants (EU Directive 2008/105/EC). The aim of this study was determination of chlorpyrifos in river and ground water, wich are widely used for irrigation in agricultural production. The Extraction of chlorpyrifos was performed using ENVI C18 SP disc (47 mm). Prior to the extraction disc was conditioned with 5 ml of acetonitrile/methanol (50/50, v/v) and 5 ml deionized water. Under vacuum 500 ml of river and ground water with added chlorpyrifos standard solutions in concentration 0.01-1.0 ug ml ', was filtered through the disc. Disc was being dried at 25°C for I h. Chlorpyrifos was eluted with 6 ml (23 ml) of acetonitrile/methanol (50/50, v/v) mixture and evaporated to dryness. The extract was diluted in 2 ml of acetonitrile/methanol (50/50, v/v). Analysis was performed with a Hewlett— Packard (HP) model 5890 Series II gas chromatograph with EC Ni®’ detector. Determination conditions were — t °C of column 190 °C with an increase of 30°C min’! up to 275°C, t°C of injector 230°C and t°C of detector 300°C. The linearity of the method was evaluated by chromatographing chlorpyrifos solution in concentrations 0.001-1.0 pg mI'. Correlation coefficient (R°) was 0.995 and limit of detection (LOD) and limit of quantification (LOQ) were 0.004 pg ml! and 0.01 wg mI', respectively. The average recovery for river water was 87.5% and for groundwater 97.9%.