间接银液滴定法测定雷贝拉唑钠肠溶片的含量
Assay of Sodium Rabeprazole Enteric Tablets by Indirect Argentimetry
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摘要: 称取一定量的题示药片,粉碎后溶于乙醇中,将溶液过滤入于100 mL棕色容量瓶中,定容后保存于冰箱中.分取一定量试样溶液,用氨水调至pH 8~9,定量加入硝酸银标准溶液后置于50 ℃水浴中加热20 min,在此反应中,该药物分子中咪唑环中氮原子上的钠离子被银离子所置换而生成雷贝拉唑银盐沉淀.过滤后,用硫氰酸铵标准溶液在pH 4~5酸度条件下滴定所得滤液,用三价铁离子作指示剂.根据所耗滴定剂的体积间接计算此药物中雷贝拉唑钠含量.经试验,该方法测定值的相对标准偏差(n=5)为0.9%,用标准加入法测得的回收率在98%~102%之间.Abstract: A definite amount of the drug tablets was weighed,pulverized and dissolved in ethanol. The solution was filtered and made up to 100 mL in a brown colored volumetric flask and kept in a refrigerator. An aliquot of the sample solution was taken and reacted in an amoniacal solution of pH 8~9,with a definite amount of standard AgNO3 solution,heated at 50 ℃ in a water bath for 20 min. During the reaction,the Na+-ion attached to nitrogen atom of the imidazole ring of the drug molecule was replaced by Ag+-ion quantitatively forming an insoluble silver salt with the drug. After filtering,the filtrate was titrated with standard NH4SCN solution at pH 4~5,with ferric ion as indicator. Content of sodium rabeprazole in the drug was calculated indirectly from the amount of titrant used. Precision of the proposed method was tested,giving value of RSD′s (n=5) of 0.9%. Recovery of the method was also tested by standard addition method,giving values of recovery in the range of 98%-102%.