酸溶-苯基荧光酮光度法测定矿样中钽

将苯基荧光酮光度法应用于矿样中Ta的测定时,Nb、Ti、Mo等元素也会与显色剂发生反应从而干扰测定。针对这一问题,实验提出采用HF-HNO₃-H₂SO₄体系分解样品,以草酸掩蔽Nb,H₂O₂掩蔽Ti,抗坏血酸和EDTA还原掩蔽Mo、Fe、V、Sn,以酒石酸和溴化十六烷基三甲基铵为络合剂,在表面活性剂聚乙烯醇存在下,用苯基荧光酮光度法对Ta进行测定,实现了矿样中Ta的分析。实验表明,Ta在0.02~1.0 μg/mL范围内符合比尔定律,线性相关系数为0.999 1,方法的检出限为0.02 μg/mL。将实验方法分别应用于锂矿石、钽矿石和稀有稀土矿这3种标准物质中Ta的测定,测得结果与认定值基本一致,相对标准偏差(RSD,n=10)为6.9%~8.5%。方法适用于野外矿样中Ta的批量测定。

Determination of tantalum in ore by phenylfluorone spectrophotometry with acid dissolution

When phenylfluorone spectrophotometry is applied for the determination of Ta in ore sample, the coexisting elements such as Nb, Ti and Mo could also react with coloring agent, which had interference with the determination. The sample was decomposed with HF-HNO₃-H₂SO₄ system. Nb was masked with oxalic acid, Ti was masked with H₂O₂, and Mo, Fe, V and Sn was reduced and masked with ascorbic acid and EDTA. The content of Ta was determined by phenylfluorone spectrophotometry with tartaric acid and cetyl trimethyl ammonium bromide as complexing agent in presence of surfactant polyvinyl alcohol. Consequently, the determination of Ta in ore sample was realized. The results showed that Beer’s law was obeyed for mass concentration of Ta in range of 0.02-1.0 μg/mL. The linear correlation coefficient was 0.999 1, and the detection limit was 0.02 μg/mL. The proposed method was applied to the determination of Ta in three certified reference materials including lithium ore, tantalum ore and rare earth ore. The results were basically consistent with the certified values, and the relative standard deviations (RSD, n=10) were between 6.9% and 8.5%. The proposed method was suitable for the determination of Ta in batch ore samples in field.