Optimization of microwave‐assisted extraction for quantification of cannabinoids in hemp tea by liquid chromatography‐mass spectrometry

Abstract

Microwave‐assisted extraction (MAE) of cannabinoids from hemp tea was optimized, for the first, using response surface methodology. The effect of temperature (50, 65, and 80°C), irradiation time (4, 7, and 10 min), and solvent‐to‐solid ratio (20, 30, and 40 mL of methanol/g of hemp tea) on cannabinoid extractability were investigated. The concentrations of five cannabinoids, namely Δ9‐tetrahydrocannabinol (Δ9‐THC), cannabidiol (CBD), cannabigerol (CBG), cannabichromene (CBC), and cannabinol (CBN), were selected as response variables. For the quantitative analysis, a liquid chromatography‐mass spectrometry method was developed and validated. The proposed analytical approach demonstrated satisfactory performance characteristics in terms of linearity (R2 ≥ 0.9998), precision (intra‐day: 1.99%–5.97% relative standard deviation [%RSD], inter‐day: 1.95%–6.08%RSD), sensitivity (limit of detection: 1.35–2.36 ng/g, limit of quantification: 4.05–7.08 ng/g) and carry‐over effect (signals ≤ 5.03%), with all cannabinoids eluting within 6 min. For comparison purposes, soxhlet extraction, ultrasound‐assisted extraction (UAE), and conventional‐stirring extraction were additionally performed. MAE proved to be a more effective technique for the extraction of CBD and CBN, while UAE managed to extract Δ9‐THC, CBG, and CBC at higher concentration levels.