Enantioseparation and determination of isofenphos-methyl enantiomers in wheat, corn, peanut and soil with Supercritical fluid chromatography/tandem mass spectrometric method

Supercritical fluid chromatography/tandem mass spectrometry (SFC-MS/MS) is an effective tool in separation science which uses the nontoxic CO2 fluid for better control of analyte retention. Also the technology of a postcolumn additive to complement MS/MS ensure the high-selectivity determination. In this paper, a green and sensitive analytical method was developed for the enantioselective separation and determination of isofenphos-methyl enantiomers in foodstuff and soil by SFC-MS/MS. The enantioseparation was performed within 3.50 min using Chiralpak IA-3 column with CO2/isopropanol (90:10, v/v) as the mobile phase at 2.2 mL/min flow rate. The postcolumn compensation technology provided with 0.1% formic acid/methanol greatly improved the ionization efficiency of mass spectrometry. Column temperature, auto back pressure regulator pressure, and flow rate of compensation solvent were optimized to 30 degrees C, 2200 psi, and 0.1 mL/min, respectively. The QuEChERs method was adopted in this study, which mean recoveries of isofenphos-methyl enantiomers ranged from 75.7% to 111.4%, with relative standard deviations less than 11.3% at three concentration levels in all matrices. The limits of detection for both enantiomers varied from 0.02 mu g/kg to 0.15 mu g/kg, while the limit of quantification did not exceed 0.50 mu g/kg. The proposed method was then successfully applied to analyze authentic samples, confirming that it was a versatile strategy for the analysis of isofenphos-methyl enantiomers in food and environmental matrices. (C) 2016 Elsevier B.V. All rights reserved.