Cannabidiol (CBD), cannabinol (CBN), and Δ9-tetrahydrocannabinol (THC) are the most important components of hemp, whose concentrations determine the properties and applications of hemp. Hemp contains a large number of impurities, which must be removed from the extracting solution before determining the cannabinol contents by ultra-high performance liquid chromatography (UHPLC). Neutral alumina, magnesium silicate, and graphitized carbon black have different surface characteristics when used as adsorbents. The removal rates of pigments, total sugar, total fatty acid glyceride, and metal ions as well as the recoveries of the three cannabinols in the extraction solution were evaluated. The amounts of neutral alumina, magnesium silicate, and graphitized carbon black were 1.80 g, 0.15 g, and 0.05 g, respectively. The three adsorbents were mixed well and packed into a polypropylene pipe to prepare a special 2 g/6 mL solid phase extraction (SPE) column for determining the three cannabinol compounds in hemp. The chemical components of the hemp flowers and leaves were extracted with an ethyl acetate/methanol (9∶1, v/v) mixture. After the extracting solution was allowed to pass through the SPE column, the recoveries of CBD, CBN, and Δ9-THC were 98.9%, 95.7%, and 99.2%, respectively. The removal rates of xanthophyll, chlorophyll a, and chlorophyll were 96.3%, 99.2%, and 95.5%, respectively. The removal rates of total sugar, total fatty glyceride, and metal ions were 98.5%, 96.9%, and 85.4%, respectively. In this study, the chromatographic conditions for analyzing the three cannabinol compounds were optimized. The cannabinol compounds were separated within 10 min on an Eclipse Plus C18 column (50 mm×2.1 mm, 1.8 μm) using a mobile phase consisting of 1% (v/v) acetic acid and acetonitrile (30∶70, v/v) at a flow rate of 0.5 mL/min. The detection wavelength was set at 210 nm with a diode array detector, and the sample injection volume was 1 μL. Good linear relationships were observed between the mass peak areas and mass concentrations of CBD, CBN, and Δ9-THC in the range of 0.5-50 mg/L. The corresponding correlation coefficients (R2) were 0.9983, 0.9995, and 0.9981, while the detection limits were 0.45 μg/L, 0.53 μg/L, and 0.38 μg/L. The recoveries of CBD, CBN, and Δ9-THC were 90.3%-96.9%, 93.7%-95.6%, and 90.8%-96.1%, with relative standard deviations (RSDs) of 2.2%-6.1%, 4.1%-8.0%, and 2.4%-4.8%, respectively. The results were satisfactory, demonstrating that the special SPE column made of neutral alumina, magnesium silicate, and graphitized carbon black was well suited for the determination of the three cannabinol compounds in hemp.
大麻中的主要成分大麻二酚(CBD)、大麻酚(CBN)和Δ9-四氢大麻酚(Δ9-THC)的含量决定了其性质和应用。在液相色谱分析中,由于大麻提取液中含有较多杂质,需要净化。该文基于大麻中CBD、CBN和Δ9-THC的结构特征及样品基质组成,根据中性氧化铝、硅酸镁和石墨化炭黑的不同表面特征,考察了这3种吸附剂对大麻提取液中叶绿素、多糖、高级脂肪酸酯及重金属离子的去除率和对3种大麻酚的回收率,确定了3种吸附剂的用量分别为1.80 g、0.15 g、0.05 g混合装填成的2 g/6 mL小柱为3种大麻酚类化合物测定的专用固相萃取柱。该小柱对大麻乙酸乙酯-甲醇提取液样品中CBD、CBN和Δ9-THC的回收率分别为98.9%, 95.7%和99.2%,对叶黄素、叶绿素a和叶绿素b的去除率分别为96.3%、99.2%和95.5%,对总糖的去除率为98.5%,对脂肪酸甘油酯的去除率为96.9%,对重金属离子的平均去除率为85.4%。优化了色谱分析条件,采用Eclipse Plus C18色谱柱(50 mm×2.1 mm, 1.8 μm),在1%乙酸水溶液-乙腈(30:70, v/v)流动相条件下等度洗脱,流速为0.5 mL/min,柱温为30 ℃,检测波长为210 nm,进样量为1 μL,在10 min内可完成样品分析。方法学考察表明,在0.5~50 mg/L范围内,CBD、CBN和Δ9-THC的液相色谱峰面积与其质量浓度呈良好的线性关系,相关系数(R2)分别为0.9983、0.9995和0.9981,检出限分别为0.45 μg/L、0.53 μg/L和0.38 μg/L,加标回收率为90.3%~97.0%、93.7%~95.6%、90.8%~96.1%,相对标准偏差(RSD)分别为2.2%~6.1%、4.1%~8.0%、2.4%~4.8%。研究结果表明,该文以中性氧化铝、硅酸镁和石墨化炭黑制作的复合型大麻酚类成分测定专用固相萃取柱在大麻植物中3种酚类化合物的测定中具有净化杂质、防止色谱柱污染的功能。由于大麻不同部位的化学成分存在差异,在后续的研究中,还要进一步考察小柱对其他杂质的去除情况,使得制备的固相萃取小柱更具有普适性。
Keywords: cannabidiol; cannabinol; hemp; special solid phase extraction column; ultra-high performance liquid chromatography (UHPLC); Δ9-tetrahydrocannabinol;.