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 has been performed, the detection of the gossypol enantiomers in vegetable oil has rarely been 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. METHODS: (-)- 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 were composed of methanol (solvent A) and water containing 0.1% formic acid (solvent B). Analytes were detected using an electrospray ionization (ESI) source in positive mode. The contents of (-)- and (+)-gossypol standard derivatives were quantified by multiple reaction monitoring (MRM) 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 min and the LODs of (-)- and (+)-gossypol were 25.55 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 and 98.96-105.14% for (+)-gossypol] and RSDs [3.41-6.02% for (-)-gossypol and 4.50-6.94% for (+)-gossypol)] were achieved. CONCLUSION: The present study confirms the feasibility of determining 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.