Determination of chlorinated phenoxy acid herbicides in tobacco by modified quechERS extraction and high-performance liquid chromatography/tandem mass spectrometry.

A new method for determination of phenoxy acid herbicide residues in tobacco based on the use of liquid extraction/partition and dispersive SPE followed by HPLC/electrospray ionization-MS/MS is reported. Formic acid (2%, v/v) in acetonitrile as the extraction solvent and inclusion of citrate buffer helped partitioning of all analytes into the acetonitrile phase. Quantitative analysis was done in the multiple-reaction monitoring mode using two combinations of selected precursor ion and product ion transition for each compound. The recoveries obtained for each pesticide ranged between 85 and 110% at two spike concentration levels. Good linear relationships were observed, with the correlation coefficient (r2) >0.998 for all analytes. The method is simple, efficient, and sensitive, and each of its performance characteristics meets the requirements for determination of phenoxy acid herbicide residues in tobacco.