热辅助下的在线甲基衍生化-气相色谱法分析银杏叶中的银杏酸

采用热辅助下的在线甲基衍生化-气相色谱法测定银杏叶中的银杏酸。银杏叶样品与衍生化试剂四甲基氢氧化铵(TMAH, 25%甲醇溶液)同时进样,在300 ℃的进样口瞬间生成了银杏酸甲基衍生物,银杏叶中6种银杏酸得到很好的分离。在一定的质量浓度范围内银杏酸的线性关系良好,回归系数均大于0.9966,最低检出限范围为0.8～2.8 mg/kg。银杏叶中主要的烷基酚类物质为银杏酸C13∶0,C15∶1和C17∶1,它们的含量(用质量分数表示)分别为11.0%,36.7%和42.8%,3次平行测定的相对标准偏差(RSD)均小于3.4%(n=3)。银杏叶样品中总银杏酸的含量为4.0～10.9 mg/g。该方法无需繁琐费时的衍生化和纯化等前处理步骤,不失为银杏叶中银杏酸测定的一种快速、简便、准确的方法。

Determination of ginkgolic acids in Ginkgo biloba leaves by gas chromatography with on-line pyrolytic methylation

A method to determine ginkgolic acids in Ginkgo biloba leaves was developed on the basis of pyrolytic methylation-gas chromatography. Pyrolytic methylation of G. biloba leaves in the injector at 300 ℃ in the presence of an organic alkali, tetramethylammonium hydroxide (TMAH, 25% methanol), allowed quantitative analysis of ginkgolic acids as their corresponding methyl derivatives. On the basis of the relative areas of these peaks, chemical composition of the ginkgolic acids in G. biloba leaves was determined with the relative standard deviations (RSDs) less than 3.4%(n=3). The calibration curves of 5 main ginkgolic acids showed good linearity with the correlation coefficients greater than 0.9966. The detection limits were between 0.8-2.8 mg/kg for the 5 compounds (S/N=3). It is a simple, accurate and highly sensitive method for the chemical analysis and quality control of ginkgolic acids in G. biloba leaves and extracts.