Polarographic determination of herbicide thifensulfuron methyl/application to agrochemical pesticide, soil, and fruit juice

A novel, sensitive, simple, fast, and fully validated differential pulse polarographic (DPP) method for the determination of trace amounts of thifensulfuron-methyl in pesticide formulation, soil, and orange juice is reported. This procedure was based on a highly sensitive peak formed due to the reduction of thifensulfuron-methyl on a dropping mercury electrode over the pH range 1.00-10.00 in Britton-Robinson buffer. The polarographic reduction exhibits only a single peak in the pH ranges pH >= 3.0 and pH <= 6.0 and pH=10.0 located at potential values of -1.010, -1.350, and -1.610 V (vs. SCE), respectively. The single peak appeared as a maximum at pH 3.0 (-1.010 V) 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, and the cathodic peak current was linearity proportional to the thifensulfuron-methyl concentration in the range of 2 x10(-7) -5x10(-5) M. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.05x10(-7) and 3.50x10(-7) M, respectively, according to the relation k x SD/b (where k=3 for LOD, k=10 for LOQ, SD is the standard deviation of the blank, and b is the slope of the calibration curve). The proposed method was applied to pesticide formulation (Harmony's(R) Extra), and the average percentage recovery was in agreement with that obtained by the spectrophotometric comparison method, 97.82 and 102.6%, respectively. The method was extended to determination of thifensulfuron-methy in spiked soil and orange juice, showing a good reproducibility and accuracy with a relative standard deviation of 4.55 and 1.40%, and relative errors of +2.80 and +1.90%, respectively.