Determination of the herbicide thifensulfuron-methyl by differantial pulse polarography

A novel differential pulse polarographic (DPP) method was developed for the determination of trace amounts of thifensulfuron-methyl in pesticide formulation, soil and orange juice. This polarographic procedure was based on an highly sensitive peak formed due to the reduction of thifensulfuron-methyl on dropping mercury electrode. The pH range studied were pH 1.0-10.0 in Britton-Robinson buffer. The polarographic reduction exhibits only a single peak in the pH ranges pH ? 3.0, pH ? 6.0 and pH = 10.0 located at potential values of -1010 mV, -1350 mV and -1610 mV (versus SCE), respectively. The single peak appeared at pH 3.0 (-1010 mV) corresponding was well resolved and suitable to be investigated for analytical use. This peak showed quantitative increments with the additions of standard thifensulfuron-methyl solution under the optimal conditions. The cathodic peak current was linearity proportional to the thifensulfuron-methyl concentration in the range of 2x10-7- 5x10-5 M. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.05 x 10-7 M and 3.50 x 10-7 M respectively. The proposed method was applied to pesticide formulation (Harmony® Extra) and average percentage recovery was found as 97.82 %. This recovery was in agreement with that obtained by spectrophotometric method (102.6 %) used for comparison. The method was applied to determination of thifensulfuron-methyl vii in spiked soil and orange juice. The results showed good repeatability and accuracy with a relative standard deviation of 4.55 % and 1.40%, and relative errors of +2.80 % and +1.90 %, respectively.