Determination of insecticide pymetrozine by differential pulse polarography/application to lake water and orange juice

A simple, fast and sensitive differential pulse polarographic method (DPP) for the determination of pymetrozine insecticide in pure form, agrochemical formulation, natural water and orange juice samples is proposed. The polarographic behavior of pymetrozine exhibited a double well-defined polarographic peaks at −580 and 950 mV (versus SCE), respectively. The peak potentials were strongly pH-dependent in that they shifted to more negative values with increasing pH. The polarographic reduction corresponding to the first peak at pH 2.0 (B–R buffer solution) showed quantitative increments with the additions of standard pymetrozine solution under the optimal conditions and the corresponding peak current was linearly proportional to pymetrozine concentration in the range of 4.97 × 10 −7 to 7.35 × 10 −5 mol L −1. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.48 × 10 −7 and 4.93 × 10 −7 mol L −1, respectively. The mean recoveries of the 5.0 × 10 −6 mol L −1 pymetrozine spiked to lake water and orange juice were (4.89 ± 0.23) × 10 −6 and (4.97 ± 0.19) × 10 −6 mol L −1 at 95% confidence level, respectively. The method was extended to the determination of pymetrozine in agrochemical insecticide formulation Plenum ® and accuracy was in agreement with that obtained by HPLC comparison method. Influences of some interfering ions and some other pesticides were also investigated. The mechanistic study was not pursued.