微波消解-硫酸亚铁铵滴定法测定钴铬烤瓷合金中铬

钴铬烤瓷合金作为齿科最常用的材料之一,尚无对应的检测标准,国内外相关的检测标准及论文报道较少,而铬作为钴铬烤瓷合金的主要成分,迫切需要开发其检测方法进而为生产、使用和贸易等方面带来重要的指导作用。采用10mL盐酸、3mL硝酸和2mL氢氟酸对样品进行微波消解,然后在硫磷混酸介质中,以硝酸银溶液作为催化剂,用过硫酸铵溶液将样品溶液中的铬(Ⅲ)氧化成铬(VI),加入硫酸锰溶液,当Mn²⁺被氧化至出现紫红色时,即可判断铬已被氧化完全,锰同时被氧化为高锰酸。加入少量氯化钠溶液并煮沸以破坏高锰酸,以苯基代邻氨基苯甲酸溶液作为指示剂,采用硫酸亚铁铵标准滴定溶液进行滴定,实现了对钴铬烤瓷合金中铬的测定。根据样品中各元素的含量范围,按照各共存元素含量最大值的2~4倍加入共存元素进行干扰试验,结果表明,在试验条件,铬的回收率为98%~100%,这说明样品中的共存元素不干扰铬的测定。将实验方法应用于钴铬烤瓷合金实际样品中铬的测定,结果的相对标准偏差(RSD,n=11)为0.49%和0.50%,加标回收率在99%~101%之间。根据样品中各元素的组成范围合成钴铬烤瓷合金模拟样品,按照实验方法进行测定,测得铬的含量与理论值相符。

Determination of chromium in cobalt-chromium ceramic alloy by ammonium ferrous sulfate titration method with microwave digestion

Cobalt-chromium ceramic alloy is one of mostly used in dentistry. So far, there is no related test standard, and there are only few reports on the related detection methods at home and abroad. Chromium is the main composition in cobalt-chromium ceramic alloy. It urgently need to develop the testing methods and provide important guidance for its production, use and trading. In experiments, the sample was treated by microwave digestion using 10mL of hydrochloric acid, 3mL of nitric acid and 2mL of hydrofluoric acid. The chromium (III) in sample solution was oxidized to chromium (VI) by ammonium persulfate in medium of sulfuric acid-phosphoric acid mixture using silver nitrate as catalyst. Manganese sulfate solution was added. It could be considered that chromium had been completely oxidized when Mn²⁺ was oxidized until purple red appeared. Meanwhile, Mn²⁺ was oxidized to permanganate. Little sodium chloride solution was added to destroy the permanganate by boiling. N-phenylanthranilic acid solution was added as the indicator for the titration using standard titration solution of ammonium ferrous sulfate. The determination of chromium content in cobalt-chromium ceramic alloy was realized. According to the content range of each element in sample, the interference tests of coexisting elements were conducted using 2-4 times of maximum content. The results showed that the recoveries of chromium were between 98% and 100% under experimental conditions, indicating that the coexisting elements in sample had no interference with the determination of chromium. The experimental method was applied for the determination of chromium in actual sample of cobalt-chromium ceramic alloy. The relative standard deviations (RSD, n=11) were 0.49% and 0.50%, and the recoveries were between 99% and 101%. According to the composition range of elements in sample, the simulated samples of cobalt-chromium ceramic alloy were synthesized and determined using the experimental method. The found results of chromium content were consistent with the theoretical values.