用在线萃取-流动注射分光光度法(FISP)测定了作为杂质与2,5-二羟基苯磺酸钙共存的对苯二酚.专门设计并制作了与流动注射分光光度测定单元组合在一起的在线萃取流路,对苯二酚用乙醚萃取进入有机相并在此相中于其吸收峰297.5 nm波长处测定其吸光度,通过萃取基体成分,即2,5-二羟基苯磺酸钙的干扰,由于其在乙醚中不溶解而得以消除.对苯二酚的吸光度与其相应浓度在3.5×10-6-5.0×10-4mol·L-1之间呈线性关系,相关系数达0.999 4.该方法的检出限为2.53×10-6mol·L-1.应用此方法分析了来自不同批次的3个试样,所得结果的RSD在069%-1.65%之间,且其值与药典法所测得结果相符.

Hydroquinone present as impurity with calcium 2,5-dihydroxy phenyl sulfonate was determined by FI-spectrophotometry with online extraction with ethyl ether.A manifold of online extraction incorporated with the FI-spectrophotometric unit was designed and fabricated especially for this purpose.Hydroquinone.was extracted into ether and its absorbance was measured at its absorption maxima of 297.5 nm in the organic phase,while the interference of the matrix compound,calcium 2,5-dihydroxy phenyl sulfonate,which is insoluble in ether,was eliminated.Linear relationship was kept between absorbance and concentration of hydroquinone in the range of 3.5×10-6～5.0×10-4mol·L-1 with a correlation coefficient of 0.999 4.Detection limit of the method was found to be 2.53×10-6mol·L-1.This method has been applied to the analysis of 3 samples from different batches of raw materials,the RSD′s (n=5) of the analyt.results obtalned were in the range of 0.69%-1.65%,and the results were also in consistency with the results obtained by the pharmacopeia method.