Residue Dynamics of Clopyralid and Picloram in Rape Plant Rapeseed and Field Soil

Abstract

A new method for simultaneous analysis of clopyralid and picloram residues in rape plant, rapeseed and field soil was developed and validated. The residual dynamics and final residues of clopyralid and picloram in rape plant, rapeseed and soil were determined by High Performance Liquid Chromtography-Diode Array Detector (HPLC-DAD) and High Performance Liquid Chromtography-Mass Spectroscopy Detector (HPLC-MSD). The limit of quantification (LOQ) was established as 0.02 mg/kg for soil sample, 0.5 mg/kg for rape and rapeseed sample, respectively. It was shown that recoveries ranged from 71.3%–109.0% for clopyralid, and 84.0%–100.5% for picloram at fortified levels of 0.02–2 mg/kg. From residue trials at two geographical experimental plots in China and laboratory simulated pots, the results showed that the half-lives of clopyralid in rape and soil were 3.66–4.83 and 2.53–5.17 days, respectively, for picloram with half-lives of 5.17–10.73 and 3.45–7.11 days. For tirals applied according to the label recommended, at harvest time the final residues of clopyralid in rapeseed were below 1.82 mg/kg, while the picloram residues could not be detected in rapeseed (<LOQ).