紫石英样品中氟化钙含量测定方法的比较

Comparison of different methods for determining the Ca F2 in Fluoritum

目的:建立中药紫石英专属性强的含量测定方法。方法:利用药典法、扣减法、酸溶法及X-粉末衍射法对38批紫石英样品进行含量测定,并利用X-粉末衍射法对样品进行物相分析。结果:物相分析结果显示,23批样品为紫石英正品,其X-粉末衍射图谱峰形尖锐简单,除氟化钙外含有少量的石英、铁等杂质;13批样品为紫石英不合格品,其X-粉末衍射图谱峰形尖锐复杂,除氟化钙外含有大量的方解石、石膏及云母族等矿物杂质;2批样品为紫石英伪品,其X-粉末衍射图谱峰形尖锐复杂,主要含有大量的碳酸盐类矿物杂质。含量测定结果显示,正品紫石英样品中氟化钙含量,X-粉末衍射法分析结果略高于药典法结果,有的可达100%,紫石英不合格品与伪品X-粉末衍射法分析结果远远小于药典法结果,表明X-粉末衍射法为半定量分析,此方法具有一定的不确定性;药典法测定结果实际为样品中包含碳酸钙等杂质在内的总钙含量,测定结果均有误差(RSD>2%);酸溶法存在二次滴定,且操作繁琐;扣减法数据在氟化钙含量较高杂质含量较低时,其数据接近药典法,当氟化钙含量较低,杂质含量较高时,其数据接近酸溶法,扣减法测定数据在药典法和酸溶法之间。结论:扣减法准确度高,专属性强。建议《中华人民共和国药典》将扣减法作为中药紫石英的含量测定方法。

Objective: To stablish accurate and specific method of Fluoritum. Methods: Thirty-eight samples of commercial Fluoritum were determined by the EDTA titrimetric method in Pharmacopoeia method, Deduction method, Acid digestion method and X-ray power diffraction method(XRD), respectively. Results: The results of XRD phase analysis showed that 23 samples were Fluoritum, the XRD patterns were simple and sharp. Fluorite was the main phase of Fluoritum, and often accompanied by a small amount of impurities such as quartz and iron. The results also indicated that 13 samples non-conformed with Fluoritum, the content of calcite, gypsum and mica group in which were high. These XRD patterns were complicated and sharp. According to the phase analysis, 2 samples were counterfeiter whose main content was carbonate minerals, the XRD patterns were complicated and sharp. The results of determination analysis showed that calcium fluoride content analyzed by X-ray power diffraction method were higher and even content to hundred, non-confirmed Fluoritum were lower when compared with Pharmacopoeia method. From determination results, it could be found that X-ray power diffraction method was semi-quantitative analysis so this method is indeterminate. It was found that the results analyzed by Pharmacopoeia method had great errors(RSD>2%) because titration outcome of Pharmacopoeia method was total calcium content contains calcium carbonate content. Acid digestion method was complicated and involve secondary titration. When analyzing the Ca F2 content in samples containing high fluorite content and low impurity content, Deduction method data closed to the Pharmacopoeia method. When analyzing the Ca F2 content in samples containing low fluorite content and high impurity content, Deduction method data close to the Acid digestion method, and Deduction method data were between Pharmacopoeia method data and Acid digestion method data. Conclusion: Deduction method is accurate and specific. In this study, the result suggest that the Deduction method should be used as the determination method for Fluoritum include in the Chinese Pharmacopoeia.