锍镍试金-电感耦合等离子体质谱法测定硫铁矿中铂族元素

摘要

Nickel sulphide fire assay is the common method to determine platinum group elements ( PGEs) for most geological samples by inductively coupled plasma-mass spectrometry (ICP-MS). However, there are few reports on pyrite samples. According to the characteristics of pyrite, which is abundant in S and Fe, routine fusion flux cannot produce an ideal nickel sulphide button, which makes the next chemical steps difficult ie dissolution and filtration. In this paper, the chemical procedure of nickel sulphide fire assay has been improved to measure the PGEs contents for pyrite by ICP-MS. The fusion flux and molten slag was changed in order to yield the ideal button without losing any of the sampling weight. The improved method gives the button the optimum capability to extract PGEs from the fusant and avoid PGEs loss from prolonged heating and reaction. As the button is easy to peel and effloresce, the procedure of button crushing is unnecessary, which not only simplifies the process, but also avoids the possibility of cross contamination. The results indicate that high content of Fe do not significantly affect the measurement of PGEs content. The whole recovery procedure was more than 94% and the detection limits of 10 g samples for Ru, Rh, Pd, Os, Ir and Pt were 0.018 ng/g, 0.017 ng/g, 0. 18 ng/g, 0.019 ng/g, 0.013 ng/g and 0. 11 ng/g, respectively. The results of different pyrite samples and standard material indicate that this method is an improvement on previous methods by meeting the requirements for PGEs determination of most pyrite.%锍镍试金常用于富集常规地质样品中的铂族元素( PGEs)；而用于富集硫铁矿中的PGEs鲜有报道.硫铁矿中硫和铁的含量较高,采用常规的试金配方不能得到较好的锍扣,影响下一步样品的溶解和过滤.本文对锍镍试金-电感耦合等离子体质谱法测定硫铁矿中PGEs的流程进行改进.针对硫铁矿中硫和铁含量高的特点,在不减少称样量的情况下,调整常规锍镍试金中的试剂配方,获得了理想的锍扣和熔渣,使锍扣富集PGEs的能力达到最佳,且避免了由于反应时间过长而造成PGEs损失.同时利用硫化铁易剥落和粉化的特点,省去了锍扣的机械粉碎工序,简化了流程,避免了碎扣时的机械损失和样品间可能的交叉污染.结果表明,高含量的铁对PGEs的测定无显著影响.加标回收试验显示PGEs全流程回收率大于94％.按10 9取样量计算,方法检出限分别为Ru 0.018 ng/g,Rh0.017ng/g,Pd 0.18 ng/g,Os 0.019 ng/g,Ir 0.013 ng/g,Pt 0.11 ng/g.实际样品分析和加标回收试验表明,改进后的锍镍试金-电感耦合等离子体质谱测定流程可以满足大多数硫铁矿中PGEs的测定要求.