Determination of chlorpyrifos in water used for agricultural production

Abstract

Chlorpyrifos is one of the most frequently used insecticide worldwide and it is more often detected in surface and ground waters compared to other organophosphorus insecticides. Also, chlorpyrifos is one of the most important water pollutants (EU Directive 2008/105/EC). In this study a solid phase extraction method was developed for determination of chlorpyrifos in surface and ground water, which are used for irrigation in agriculture production, Samples were prepared by spiking in 500 ml of water (surface and ground) with standard chlorpyrifos solution at rates 0.01-1 g/ml. Extraction was carried out using ENVI C18 SP disc (47mm; Supelco No. 57171). Prior to extraction, the disc was conditioned with 5 ml of acetonitrile/methanol (50/50, v/v) mixture and 5 ml of deionised water. Chlorpyrifos was eluted from the disc with 6 ml (2x3 ml) of acetonitrile/methanol (50/50, v/v). Eluent was evaporated till dry, than diluted in 2 ml of acetonitrile/methanol (50/50, v/v) and homogenised with ultrasound. Chlorpyrifos content was analyzed using gas chromatograph (HP 5890 series II) with EC Ni® detector (column SUPELCO 24048, SPB'™-S, 30mx0.32mm, 0.25um FILM; gas carrier He). Injected volume was 2ul. Determination conditions were — column temperature 190°C, increase of 30°C/min, final temperature 275°C; injector temperature 230°C; detector temperature 300°C. Linearity of detected response was determined by injecting standard chlorpyrifos solution at rates 0.001-1.0 pg/ml. Correlation coefficient (R°) was 0.995 %. Limit of detection (LOD) for analyzed chlorpyrifos was estimated from the fortified samples, while the limit of quantification (LOQ) was calculated from LOD. LOD and LOQ were 0.004 pg/ml and 0.01 pg/ml, respectively. Average recoveries of chlorpyrifos detection method in surface water were ranged from 84 % to 89 %, and in groundwater from 87 % to 95 %.