Dissipation and residue behavior of mepiquat on wheat and potato field application.

A modified LC-MS method for the analysis of mepiquat residue in wheat, potato, and soil was developed and validated. A hydrophilic interaction liquid chromatographic column has been successfully used to retain and separate the mepiquat. Mepiquat residue dynamics and final residues in supervised field trials at Good Agricultural Practice (GAP) conditions in wheat, potato, and soil were studied. The limits of quantification for mepiquat in all samples were all 0.007 mg kg(-1), which were lower than their maximum residue limits. At fortification levels of 0.04, 0.2, and 2 mg kg(-1) in all samples, recoveries ranged from 77.5 to 116.4% with relative standard deviations of 0.4-7.9% (n = 5). The dissipation half-lives (T 1/2) of mepiquat in soil (wheat), wheat plants, soil (potato), and potato plants were 4.5-6.3, 3.0-5.6, 2.2-4.6, and 2.4-3.2 days, respectively. The final residues of mepiquat were below 0.153 mg kg(-1) in soil (wheat), 0.052-1.900 mg kg(-1) in wheat, below 0.072 mg kg(-1) in soil (potato), and below 1.173 mg kg(-1) in potato at harvest time. Moreover, pesticide risk assessment for all the detected residues was conducted. A maximum 0.0012% of acceptable daily intake (150 mg kg(-1)) for national estimated daily intake indicated low dietary risk of these products.