Determination of Haloxyfop-methyl and Its Metabolites in Tobacco by Dispersive Solid-Phase Extraction Coupled with Liquid Chromatography-Mass Spectrometry

A method was developed for determination of haloxyfop-methyl and its metabolite haloxyfop in tobacco leaves using dispersive solid phase extraction-high performance liquid chromatography-tandem triple quadrupole mass spectrometry (HPLC-MS/MS). Under alkaline condition (pH≥10), haloxyfop-methyl and its conjugate in samples were hydrolyzed to haloxyfop. The samples were extracted by acetonitrile, purified by dispersive solid phase extraction, and detected by HPLC-MS/MS. The average recoveries were 93%-99% and the relative standard deviations (RSDs) were 3.1%-4.9% when haloxyfop-methyl was added at 0.02-1.0 mg/kg in fresh tobacco leaves. The average recoveries were 92%-96% and the RSDs were 3.3%-4.6% when haloxyfop-methyl was added at 0.05-1.0 mg/kg in dry tobacco leaves. The linear relationships between the standard curves of fresh and dry tobacco leaves were good in the range of 0.005-1.0 mg/kg, and the correlation coefficients were all greater than 0.99. The limit of quantitations (LOQs) of haloxyfop-methyl in fresh tobacco leaves and dry tobacco leaves were 0.02 mg/kg and 0.05 mg/kg, respectively. The residue of haloxyfop-methyl in both fresh and dry tobacco leaves were lower than its LOQs. This method is simple, reliable, efficient, and rapid, and is suitable for the determination of haloxyfop-methyl and its metabolite haloxyfop residues in tobacco samples.