Residue Analysis of Fluroxypyr-meptyl in Wheat and Soil by GC–ECD

Abstract

A simple and reliable analytical method for fluroxypyr-meptyl residues in wheat and soil was established. The residual levels and dissipation rates of this pesticide in wheat and soil were determined by gas chromatography with electron capture detector (GC-ECD). Samples of wheat grains and soil were extracted with methanol-water, and then liquid-liquid partitioned with dichloromethane. The extracts were further cleaned up by solid-phase extraction (SPE) with Florisil cartridges (500 mg, 3 mL), and eluted with petroleum ether-acetic ether (95/5, v/v). The eluate was collected and concentrated for GC-ECD analysis. The results showed good linearity (r 2 = 0.999) over the concentration range of 0.01-1.0 lg mL -1 . Limits of quantification (LOQ) of the method were 0.005 mg kg -1 for both soil and wheat grains. Average recoveries for the wheat grains and soil samples were 84.45-108.2% and 95.33-106.6%, respectively, and the corresponding relative standard deviations (RSDs) of the recovery data were 0.819-3.77% and 1.55-5.28% for the three fortified levels (0.005, 0.1, 0.5 mg kg -1 ). The half-life of fluroxypyr-meptyl in soil from experimental field was 1.93 days (in Beijing) and 3.01 days (in Tianjin). The final residue of the pesticide in wheat and soil was lower than 0.005 mg kg -1 , respectively, at harvest time. The analytes in real samples were further confirmed by gas chromatography-mass spectrometry (GC-MS). It was demonstrated that the proposed method was simple and efficient, and particularly suitable for detecting fluroxypyr-meptyl residues in wheat and soil.