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

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.