ANALYTICAL VALIDATION METHOD FOR THE DETERMINATION OF SULFONYLUREA HERBICIDES IN WATER SAMPLES BY SOLID-PHASE EXTRACTION AND HPLC WITH DIODE-ARRAY DETECTION

Pesticides having different structures and biological activities are widely used for agricultural and non-agricultural purposes. Due to their widespread use, pesticides need to be determined in various environmental matrices. A wide range of analytical techniques have been developed in order to identify the organic contaminants often present at trace levels in environmental samples. The aim of this work was to develop a reliable, rapid, robust and cost-effective method for the determination of five sulfonylurea herbicides (nicosulfuron, oxasulfuron, tribenuron methyl, triasulfuron and tritosulfuron) in spiked river water samples. The samples were diluted with 0.5% acetic acid (1:1) and purified by solid-phase extraction (SPE) on Oasis MAX cartridges. After the cartridges were sequentially washed with water, methanol, ethyl acetate, and acetonitrile, they were eluted with 0.1% formic acid in acetonitrile. Elutes were evaporated to dryness and reconstituted in acetonitrile. The purified extracts were analyzed by reversed-phase high-performance liquid chromatography with diode-array detection (HPLC-DAD) system. The best separation was achieved on a Zorbax Eclipse XDB-C-18 (50mm x 4.6mm x 1.8 mu m) analytical column with gradient elution at a flow rate of 1 mL/min. The analyte was monitored at 230 nm. The linearity of calibration curve within the tested concentration range exhibited correlation coefficients (r(2)) higher than 0.998. The accuracy of the method was acceptable since the average recoveries measured at two fortification levels were in the range of 92.5-97.5% (n=3). The precision of the developed procedure expressed as the relative standard deviations (RSDs) were lower than 4.76% in all cases. The repeatability of the retention time and peak area was checked by injecting standard solution ten times. The relative standard deviation of the retention time and the peak area was found to be less than 0.2% and 0.6%, respectively. The method was also validated by analyzing freshly spiked river water samples. The proposed analytical method might be successfully applied in monitoring of sulfonylurea herbicides (nicosulfuron, oxasulfuron, tribenuron methyl, triasulfuron and tritosulfuron) in surface water and groundwater samples.