泡塑分离富集-火焰原子荧光光谱法测定地球化学样品中的痕量金

Determination of Trace Gold in Geochemical Samples by Flame Atomic Fluorescence Spectrometry with PUFP Separation and Enrichment

火焰原子荧光光谱法(FAFS)测定痕量金的灵敏度好、稳定性高及线性范围广,但在测定时干扰极为严重,如果干扰元素不加以分离或扣除,对0.5ng/g以下金无法进行准确测定。本方法在传统泡塑分离富集金的基础上,研究了FAFS法测定痕量金的最佳条件:在选定仪器条件下,提出了选择低背景值(≤0.25ng/g Au)泡塑分离富集Au,采用3.0g/L硫脲-1%盐酸为解脱液可消除记忆效应,在标准系列中加入5μg/mL的Fe3+溶液扣除铁对测定金的干扰。采用本分析方法对国家标准物质GBW07805、GBW07242、GBW07244a、GBW07245a和GBW07247进行测定,相对误差≤4.7%,相对标准偏差(RSD)≤23.2%;采用FAFS法与ICP-MS法对90个原生晕样品和4个控制样品中痕量金同时进行测定,两组测定结果数统计分析的F检验值为1.23,相关系数为1.01,符合性较好,无显著性差异。本分析方法简便、快速与实用,金检出限为0.08ng/g,线性范围为0.08~500ng/g,可达3个数量级。

BACKGROUND: The detection sensitivity, stability, and linear range of Au using flame atomic fluorescence spectrometry(FAFS) is comparable to the method of inductivity coupled plasma-mass spectrometry(ICP-MS). When Au concentration is below 0.5 ng/g, it is difficult to accurately determine Au if the interference elements in FAFS are not separated and eliminated.OBJECTIVES: To optimize the conditions during determination of trace Au by FAFS method.METHODS: The optimized conditions for trace Au detection using FAFS were provided based on the conventional Au separation and enrichment method of polyurethane foam plastics(PUFP). Using the thiourea(3.0 g/L) and HCl(1%) as desorption solution can effectively eliminate the Au memory effect after separation by PUFP with low Au background value(≤0.25 ng/g), and 5μg/mL of Fe3+ solution added into Au standard solutions was used to eliminate the interference during Au detection using FAFS.RESULTS: The method was used to analyze national standard materials GBW07805, GBW07242, GBW07244 a, GBW07245 a and GBW07247, which yielded the relative error(RE) and relative standard deviation(RSD) of less than 4.7% and 23.2%, respectively. The Au contents for 90 primary halo samples and 4 monitor samples were analyzed simultaneously using FAFS and ICP-MS. Results showed that no significant differences existed between the two methods with F=1.23 and the correlation coefficient of 1.01, which further proved the accuracy and reliability of FAFS. CONCLUSIONS: FAFS is simple, convenient, fast and practical. Method detection limit of Au is as low as 0.08 ng/g, and the linear range(0.08-500 ng/g) is three orders of magnitude.