Residue Determination and Monitoring of the Levels of Metsulfuron Methyl in Selected Rivers at Tasik Chini, Pahang, Malaysia

The levels of metsulfuron methyl (methyl 2-(4-methoxy-6-methyl-1,3,5-trazine-2-ylcarbamoylsulfamoyl) benzoate (IUPAC) (MSM) and its metabolite IN-A4098 (4-methoxy-6-methyl-1,3,5-triazine-2-amine (AMMT) were determined from surface water samples of six rivers located at Tasik Chini, Pahang, Malaysia. The optimization analytical method was developed for the determination of the MSM herbicide and its metabolite, AMMT in surface water up to 0.05 ng/ml with good linearity in the calibration range 0.1 - 10 ng/ml. The procedure involves a clean-up process using the IST ISOLUTE ENV+ solid phase extraction (SPE) method and the pesticide level are determined using the HPLC with variable wavelength detector (VWD) and 81 - 105 % recovery. The MSM compound represents one of main herbicides used in the Tasik Chini oil palm plantation. The method enables study to be made of the herbicide and its transformation products through simultaneous detection and quantification. In the field study levels of MSM in the surface water ranged from undetectable to 0.1378 ng/ml from the first season to forth season, while levels of the metabolite, AMMT ranged from undetectable to 1.473 ng/ml. The variation of the MSM and AMMT levels depended directly on the time of the pesticide application and the season. (author)