Stereoisomeric separation of the chiral herbicide profoxydim and residue method development in rice by QuEChERS and LC-MS/MS.

A method for the simultaneous determination of the four stereoisomers of the chiral herbicide profoxydim in rice and husk was developed using the QuEChERS method and LC-tandem mass spectrometry. Four polysaccharide-based chiral stationary phase columns were evaluated. All four stereoisomers were successfully separated on a Chiracel OJ-3R column. The effects of mobile phase, modifiers, mobile phase flow rate and temperature on the separation were also investigated. Different QuEChERS methods were compared for the development of an optimized sample preparation procedure. The method, following SANTE guidelines, showed excellent linearity (R ≥ 0.99), the LODs were below 4.0 µg kg, and the LOQs did not exceed 12.5 µg kg. The overall average recoveries at three levels (12.5, 25.0 and 250 µg kg) ranged from 76.77 % to 106.53 %, with RSD values less than 7 %. The method is demonstrated to be convenient and reliable for the routine monitoring of profoxydim stereoisomers in rice and husk.