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 °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 μg/kg to 0.15 μg/kg, while the limit of quantification did not exceed 0.50 μg/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.