微波消解-石墨炉原子吸收光谱法测定痕量银的研究

Determination of trace amounts of silver by microwave digestion graphite furnace atomic absorption spectrometry

传统的应用石墨炉原子吸收光谱法测定化探样品中的痕量银,一般采用盐酸-硝酸-氢氟酸-高氯酸电热板加热溶样,使用铱、铂为基体改进剂,但存在分析流程繁琐、成本高等缺点。相比于电热板消解法,微波消解技术的高压密闭消解和微波快速加热等特点,具有酸用量少、消解完全、消解过程损失少等优点。本文对传统的微波消解和仪器工作参数进行了改良,确定了最佳测定条件。建立了HNO_3-H_2O_2高压密闭消解样品,石墨炉原子吸收法测定水系沉积物、土壤、岩石中痕量银的方法。采用65%的HNO_3和H_2O_2微波消解溶样,加入12 g/L硫脲为介质,消除了基体干扰。方法检出限为0.018μg/g,将所建立的分析方法用于沉积物标准物质(GBW07309、GBW07311)、土壤标准物质(GBW07402、GBW07404)和岩石标准物质(GBW07103、GBW07104)验证,结果显示测定值与推荐值吻合,准确度△lg C(GBW)≤±0.024、RE(GBW)≤±5.71%,精密度RSD(GBW)≤5.97%。该分析方法适用于大批化探样品中痕量银的测定。

A method for determination of trace silver in stream sediments,soils and rocks by graphite furnace atomic absorption spectrometry(HNO3-H2 O2) was developed in this study.The microwave digestion and instrument working parameters were optimized and the optimum conditions were determined.In traditional method,determination of trace silver in geochemical exploration samples is conducted by graphite furnace atomic absorption spectrometry through heating the hydrochloric acid nitric acid hydrofluoric acid and perchloric acid electric heating plate digestion,with iridium,platinum as matrix modifier;the analytical process is complex,and the cost is high.Compared with the electric heating plate digestion method,the microwave digestion technique is characterized by highpressure closed digestion with small amounts of acid,complete digestion and less loss in the digestion process.In this paper,HNO3(65%) and H2O2 microwave digestion was used to dissolve the matrix interference by adding 12 g/L thiourea as the medium.The detection limit was 0.018 μg/g,and the analytical method was used for verification of sediment reference materials(GBW07309,GBW07311),soil standard substance(GBW07402,GBW07404) and rock reference materials(GBW07103,GBW07104).The measured results were consistent with the recommended values,the accuracy of lg C(GBW) is △lg C(GBW)≤± 0.024,RE(GBW)≤± 5.71%,the precision of RSD(GBW) is ≤5.97%.The method is suitable for the determination of trace silver in a large amount of geochemical samples.