Fluorometric determination of asulam in water by using solid-phase extraction.

Abstract

A fluorometric determination method for asulam(methyl4-aminosulphonylcarbamate, herbicide) in environmental water samples by using solid-phase extraction(SPE) has been proposed. The method is based on the addition of EDTA to a sample solution for the elimination of interferences from metal ions and the use of ethylsilanized silica(tC2) and polystyrene gel(PS-2) combination cartridges to remove any fluorescent impurities in the matrix. Asulam in a sample solution(pH2∼3) was hardly retained in the tC2 combined upon the PS-2, and retained in the PS-2. Asulam, which was slightly adsorbed on the tC2, was retained in the PS-2 by washing with 20ml of water. Asulam was then eluted from the PS-2 with 2ml of methanol. After adjusting the pH to 8∼10 and diluting to 10ml, asulam was determined by measuring the fluorescence intensity at 343nm with excitation at 252nm. The calibration graph was linear over the range of 0.02 to 0.3mgl-1(r=0.997). The average recovery of 0.25mgl-1 asulam in 100ml of distilled water was 98.9%(n=5) with a relative standard deviation of 1.16%. The proposed method has been successfully applied to some environmental water samples with recoveries of 93∼96%.