甜菊素中总甜菊糖苷的定量分析方法之比较

Comparison of quantitative determination of total steviol glycosides in steviosin

甜菊糖苷在药用辅料中被称为甜菊素,其总甜菊糖苷的定量分析依据中国药典的容量分析法;而在食品应用中,总甜菊糖苷的定量分析依据国标GB8270-2014的反相HPLC法。两类方法的检测原理和结果不尽相同,因而会给实际应用带来困扰。本文分别采用容量分析法、正相HPLC法和反相HPLC法测定七种市售甜菊素和一种葡萄糖基甜菊糖苷中的总甜菊糖苷含量;并以红外光谱分析上述甜菊糖样品和其他合成甜味剂。实验结果表明,个别市售甜菊素中可能有外加其他甜味剂。分别依据药典和国标的方法分析所试样品的总甜菊糖苷含量,依据药典所得结果相对依据国标所得结果基本为负偏差,最大相对偏差可达-16.04%。容量分析法因为其最终结果以斯替夫苷当量计算,所以比较适用于测定平均分子量接近斯替夫苷分子量的产品;而液相色谱法由于考虑了11种甜菊糖苷,与实际结果将较为接近。建议用反相HPLC法检测甜菊素中总甜菊糖苷的含量。

The methods for quantitative determination of total steviol glycosides can be the volumetric analysis by Chinese Pharmacopoeia or high performance liquid chromatography based on National standard of GB8270-2014,respectively. However,the principles and the analysis are different in these two methods,often cause the confusion. In this study,the content of total steviol glycosides in seven commercial steviosin and a glucosylized steviol glycosides product were analyzed using volumetric and HPLC,respectively. Their IR spectrum were also presented. The experimental results show since sample might contain other synthetic sweetener,the volumetric method presented negative deviation up to-16.04% compared with the results by GB8270-2014. The conclusion is that the volumetric method is more suitable for samples which the average molecular weight of steviol glycosides is close to that of stevioside,because it is based on the equivalent of stevioside;while HPLC is more suitable for the quantitative determination of total steviol glycosides in steviosin,especially by RP-HPLC.