Specific determination of (-)- and (+)-gossypol in vegetable oil by ultra-performance liquid chromatography-tandem mass spectrometry with chiral pre-column derivatization

Abstract Background As the unique ingredient of cottonseed oil, gossypol is toxic and there are differences between the enantiomers. Although the determination of (-)- and (+)-gossypol in cotton plants or cottonseed was performed, the detection about the gossypol enantiomers in vegetable oil was rarely reported. Objective To develop a specific inspection method for (-)- and (+)-gossypol in vegetable oil by ultra-performance liquid chromatography (UPLC) -tandem mass spectrometry with chiral pre-column derivatization. Method (-)- and (+)-gossypol were separated on an ACQUITY C18 reverse phase column (100 mm × 2.1 mm, 1.7 μm) maintained at 40 °C on an UPLC system with gradient elution. The mobile phases was composed of methanol (solvent A) and water containing 0.1% formic acid (solvent B). Analytes were detected with Electron Spray Ionization source in the positive mode. The contents of (-)- and (+)-gossypol standard derivatives were quantified by Multiple Reaction Monitoring with the transitions of m/z 633/483 for quantitative ion pairs and m/z 633/558 for qualitative ion pairs. Results The results indicated that the quantitative analysis could be accomplished within 12.5 minutes and the limits of detection of (-)- and (+)-gossypol were 25.55 μg/kg and 14.67 μg/kg, respectively. When this method was applied to olive oil spiked with gossypol standards, good recoveries (95.37%-105.84% for (-)-gossypol, 98.96%-105.14% for (+)-gossypol) and RSDs (3.41%-6.02% for (-)-gossypol, 4.50%-6.94% for (+)-gossypol) were achieved. Conclusion The present study confirms the feasibility of determining the gossypol enantiomers and achieves trace determination of (-)- and (+)-gossypol in vegetable oil. These results make this method more suitable for the qualitative identification of whether the vegetable oil has been mixed with cottonseed oil. Highlights The trace determination of (-)- and (+)-gossypol in vegetable oils has been achieved. This method provides technical support for further identification of whether commercially available vegetable oil has been mixed with cottonseed oil.