Determination of 3 Cannabinols in Puffed Foods by Ultra-High Performance Liquid Chromatography- Tandem Mass Spectrometry with Dispersive Solid Phase Extraction Optimized by Response Surface Methodology

The method mentioned by the title was proposed after optimizing amounts of purification agent and extraction solvent by single factor and response surface methodology. The 2 g of crushed puffed food sample was taken, and 10 mL of water, 10 mL of acetonitrile, 4 g of anhydrous magnesium sulfate and 1 g of sodium chloride were added in sequence. The mixture was vortexed for 15 min and centrifuged for 5 min, and 2 mL of supernatant was taken and placed into a centrifuge tube containing 200 mg of octadecylsilane bonded silica gel (C₁₈) and 30 mg of N-propylethylenediamine (PSA). After vortexing for 2 min, and centrifuging for 5 min, the supernatant was passed through a 0.22 μm filter membrane, and the filtrate was determined by ultra-high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UHPLC-Q-TOF/MS). Cannabidiol, cannabinol and tetrahydrocannabinol in the filtrate were separated by gradient elution with mixed solutions of 0.1% (volume fraction) aqueous ammonia solution and acetonitrile at different volume ratios on the Agilent Extend C₁₈ chromatographic column, ionized by negative ion mode of electrospray ion source, and quantified by matrix matching method. It was shown that the established three-factor three-level response surface model was a quadratic regression equation with correlation coefficient of 0.994 9. Under the optimal conditions (C₁₈, PSA, and acetonitrile amounts of 200 mg, 30 mg, and 10 mL, respectively), the experimental value (94.1%) and predicted value (93.6%) of the tetrahydrocannabinol recovery were consistent. Linear relationships between values of the mass concentrations of the 3 targets and peak areas of the corresponding parent ions were kept in the range of 5.0-200 μg·L⁻¹, with the same detection limit (3S/N) of 10.0 μg·kg⁻¹. Test for the spiked recovery at the 3 concentration levels was conducted on negative rice cakes, giving recoveries in the range of 81.9%-94.1%, and RSDs (n=6) of the determined values ranged from 3.9% to 7.3%. The proposed method was used for the analysis of samples of rice cakes, biscuits, and potato chips samples. Cannabinol (27.8 μg·kg⁻¹), cannabidiol (113 μg·kg⁻¹) and tetrahydrocannabinol (30.6 μg·kg⁻¹) were detected in one imported biscuit sample, while these 3 targets were not detected in the other samples.