针对现有方法有机试剂消耗量大、测定值与标签值不一致等问题,提出了题示方法。称取约0.1 g样品,撕掉防黏层后置于顶空瓶中,加入5 mL N,N-二甲基甲酰胺(DMF)后振荡10 s,于80℃处理1 h。分取2 mL并离心1 min,取上清液100 μL,用乙酸乙酯定容至1 mL,供气相色谱仪分析。用VF-17ms毛细管色谱柱分离薄荷脑,用火焰离子化检测器(FID)检测。结果显示:薄荷脑的质量浓度在10~500 mg·L^-1内与其对应的峰面积呈线性关系,检出限(3S/N)为0.02 mg·kg^-1;对实际样品进行精密度以及回收试验,测定值的相对标准偏差(n=6)为1.4%,回收率为97.1%~103%;与《中华人民共和国药典》2020年版中检测薄荷脑粉末的方法进行比对,两种方法存在显著性差异,部分药典方法测定值低于标签值;方法用于6个实际样品的分析,取得了满意结果。

In view of the large consumption of organic reagent and inconsistency between the determined value and the label value in the existing methods, the method as mentioned by the article was proposed. About 0.1 g of the sample was taken and placed into a headspace bottle after removing the anti-stick layer. After 5 mL of DMF was added, the mixture was shaken for 10 s, and heated at 80 ℃ for 1 h. An aliquot (2 mL) of the solution obtained was taken and centrifuged for 1 min. The supernatant of 100 μL was taken, diluted to 1 mL with ethyl acetate, and analyzed by gas chromatograph. Menthol was separated by VF-17ms capillary chromatographic column, and detected by flame ionization detector (FID). As found by the results, mass concentrations of menthol showed a linear relationship with peak areas in the range of 10-500 mg·L^-1, with detection limit (3S/N) of 0.02 mg·kg^-1. Tests for precision and spiked recovery were made on actual samples, and RSDs (n=6) of the determined values was 1.4%, giving recoveries in the range of 97.1%-103%. Compared with the method for detection of menthol powder in the pharmacopoeia of the People's Republic of China (2020 edition), there was a significant difference between the 2 methods, and some values determined by the pharmacopoeia method were lower than the label values. The proposed method was used for the analysis of 6 actual samples, and satisfactory results were obtained.