氢化物发生-原子荧光光谱法间接测定中草药中的稀土元素

稀土元素的化学性质十分相似，能与偶氮胂Ⅲ结合生成稳定的配位化合物，该配位化合物在二苯胍的作用下易被萃取到正丁醇中，再利用减压蒸馏法将有机相蒸干后用稀HCl溶解，加高锰酸钾溶液释放出配位化合物中的As后，用原子荧光光谱法测定As从而间接测定稀土元素。本法以硫酸铈为标准溶液对实验的萃取条件、KMnO₄用量、蒸馏温度、偶氮胂Ⅲ用量、干扰离子等条件进行了优化，并采用国家标准物质对方法的精密度和准确度进行验证，测定结果与标准值能很好吻合。在最优条件下，方法检出限为0.44 μg·mL-1，线性范围为0.2～25 μg·mL-1。采用低温灰化，HNO₃-H₂O₂消化法处理中草药样品，测定结果满意，相对标准偏差为1.3%～2.5%，加标回收率为94.4%～106.0%。该法该法简便快速，仪器设备简单，准确度高。将稀土元素富集到有机相，使待测元素与基体分离;将有机相蒸干后酸溶解试样，水相进样能避免有机溶剂对泵管的影响。

Indirect Determination of Rare Earth Elements in Chinese Herbal Medicines by Hydride Generation-Atomic Fluorescence Spectrometry

Based on their similarity in chemical properties, rare earth elements were able to form stable coordinated compounds with arsenazo Ⅲ which were extractable into butanol in the presence of diphenylguanidine. The butanol was removed under reduced pressure distillation; the residue was dissolved with diluted hydrochloric acid. As was released with the assistance of KMnO₄ and determined by hydrogen generation-atomic fluorescence spectrometry in terms of rare earth elements. When cesium sulfate worked as standard solution, extraction conditions, KMnO₄ amount, distillation temperature, arsenazo Ⅲ amount, interfering ions, etc were optimized. The accuracy and precision of the method were validated using national standard certified materials, showing a good agreement. Under optimum condition, the linear relationship located in 0.2~25 μg·mL-1 and detection limit was 0.44 μg·mL-1. After the herbal samples were digested with nitric acid and hydrogen peroxide, the rare earth elements were determined by this method, showing satisfactory results with relative standard deviation of 1.3%~2.5%, and recoveries of 94.4%~106.0%. The method showed the merits of convenience and rapidness, simple instrumentation and high accuracy. With the rare earths enriched into organic phase, the separation of analytes from matrix was accomplished, which eliminated the interference. With the residue dissolved by diluted hydrochloric acid after the solvent was removed, aqueous sample introduction eliminated the impact of organic phase on the tubing connected to pneumatic pump.