Enantioselective determination of carboxyl acid amide fungicide mandipropamid in vegetables and fruits by chiral LC coupled with MS/MS.

An efficient enantioselective method for the determination of mandipropamid in vegetables and fruits was presented by LC coupled with MS/MS. The mandipropamid residues in samples (potato, pepper, grape, and watermelon) were extracted with acetonitrile containing 1% acetic acid. An aliquot was cleaned up with primary and secondary amine and C18 sorbent. Complete enantioseparation of mandipropamid enantiomers in <4 min was obtained on a Lux Cellulose-2 column at 25°C using methanol with 0.1% formic acid/0.1% aqueous formic acid solution (85:15, v/v) as mobile phase. Good linearity was obtained over the concentration range of 0.5-250 μg/L for each enantiomer in the standard solution and sample matrix calibration curves. Quantification was achieved using matrix-matched standard calibration curves. The interday mean recoveries, intraday repeatability, and inter-day reproducibility varied from 76.4 to 97.1%, 3.4 to 9.4%, and 3.5 to 11.4%, respectively. The limits of quantification for mandipropamid enantiomers in vegetables and fruits were both 1 μg/kg. Moreover, the absolute configuration of mandipropamid enantiomers was determined by the combination of experimental and predicted electronic circular dichroism spectra, and the first eluted enantiomer was confirmed as (R)-mandipropamid on five chiral columns.