Determination of eight cannabinoids in foods with enhanced matrix removal-lipid adsorbent by ultra performance liquid chromatography-tandem mass spectrometry

Abstract

A novel method was developed for the simultaneous determination of eight cannabinoids in six types of food matrices, including chocolate, fondant, biscuit, beverage, cookie and baijiu, using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample extraction and cleanup steps were optimized, and various purification methods were investigated to remove the oil matrix and glue in chocolate and fudge, respectively. Enhanced matrix removal-lipid adsorbent (EMR-Lipid) provided efficient, selective cleanup of the evaluated matrices. The sample was extracted using acetonitrile, followed by EMR-Lipid cleanup, and then dried using anhydrous sodium sulfate. The acetonitrile layer was concentrated by nitrogen to near-dry after 100 μL 10% glycerol in methanol was added to improve the recovery by reducing loss during concentration under the stream of nitrogen gas. Eight cannabinoids were separated using a Waters ACQUITY UPLC BEH Shield RP18 column (100 mm×3.0 mm, 1.7 μm). The responses of the cannabinoids in the positive and negative ionization modes were investigated and optimized, and the responses were superior in the negative ion mode compared to those in the positive ion mode. MS detection was performed in the multi-reaction monitoring (MRM) mode using an electrospray source in the negative ion mode. The cannabinoids were quantified using an external standard with matrix calibration curves to reduce the influences of the matrix effects on the quantitative results. The developed method was verified, and the conditions of sample pretreatment were also optimized. The calibration curves of tetrahydrocannabinol, cannabidivarin, tetrahydrocannabivarin, and cannabigerol and those of cannabidiol, cannabinol, cannabidiolic acid, and tetrahydrocannabinolic acid exhibited good linearities, with r>0.995, in the ranges of 2-200 and 0.4-40 ng/mL, respectively. The respective limits of detection (LODs, S/N=3) and quantification (LOQs, S/N=10) of tetrahydrocannabinol, cannabidivarin, tetrahydrocannabivarin, and cannabigerol were 4 and 10 μg/kg, and those of cannabidiol, cannabinol, cannabidiolic acid, and tetrahydrocannabinolic acid were 0.8 and 2 μg/kg. The average recoveries of the cannabinoids were 82.0%-114.9% under three spiked levels with corresponding relative standard deviations (RSDs) of <15% (n=6). EMR-Lipid provided efficient, selective cleanups of food matrices with good accuracy. The method is sensitive, rapid, accurate, simple to execute, and it is suitable for the determination of cannabinol compounds in typical food matrices.