PE-HPLC/DAD analysis of bentazone and azinphos-methyl in water sample

A simple and reliable method was developed for the determination of bentazon and azinphos-methyl in water using high-performance liquid chromatography with diode array detection (HPLC-DAD) at 254 nm. Chromatographic separation was carried out on a BDS Hypersil C8 column (15 0mm x 4mm, 5 µm particles) at 200C and 0.8 ml/min flow rate with a mobile phase consisting of acetonitrile - ultrapure water (80 : 20, v/v). Satisfactory separation of two pesticides was obtained in 7 minutes by injecting 10µl standard solution. The linearity ranges of the calibration curves ranged from 0.27 µg/ml to 2.47 µg/ml for bentazon and from 0.34 µg/ml to 3.1 µg/ml for azinphos-methyl. The selectivity of the method was tested by injecting standard solution containing a mixture of azinphos-methyl, bentazon, atrazine, simazine and propazin. These compounds were separated at differents retention times, this showing the selectivity of method. The recovery rate was tested using two SPE cartridges: Strata X (Phenomenex) and LiCrholut EN (Merck). The Strata X cartridges were found to be more suitable for extracting the two organophosphorus pesticides from surface water samples. The average recoveries were 95.8% for azinphos-methyl and 105.6% for bentazon.