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微波消解电感耦合等离子体质谱法测定地球化学样品中钒铬镍锗砷

Simultaneous Determination of V, Cr, Ni, Ge and As in Geochemical Samples by ICP-MS Combined with Microwave Digestion Sample Preparation

  • 摘要: 地质样品中多种元素的分析,通常采用高压密封消解电感耦合等离子体质谱法(ICP-MS),而应用于测定地球化学样品中的V、Cr、Ni、Ge、As等元素,影响分析准确度的主要原因有:样品前处理方面,高压密封罐会释放Cr和Ni污染样品,同时Ge和As属于易挥发元素容易造成损失;质谱测定方面,多原子分子离子会产生干扰。本文针对两方面的干扰因素,对比了微波消解硝酸提取、微波消解王水提取、高压密封硝酸复溶、高压密封王水复溶四种前处理方法中待测元素的溶出效果以及污染或损失情况。结果表明,采用微波消解替代高压密封罐消解可消除引入的Cr、Ni污染,避免了Ge、As挥发损失,同时微波消解的时间短。而采用硝酸提取,由于避免了氯的引入,分析效果优于王水提取。且使用八极杆ICP-MS氦气碰撞模式消除了样品基体中的氯多原子分子离子干扰(如37Cl14N对51V干扰,35Cl16OH对52Cr干扰,35Cl37Cl对72Ge干扰以及40Ar35Cl对75As干扰等)。应用微波消解硝酸提取、ICP-MS测定岩石、水系沉积物和土壤国家标准物质,V、Cr、Ni、Ge、As的检出限分别为1.09、0.19、0.55、0.02、0.50 μg/g,精密度(RSD) < 4%,而采用高压密封消解、ICP-MS测定V、Cr、Ni的检出限为3.48、13.09、21.67 μg/g(Ge和As由于挥发无法用此法检测)。运用微波消解硝酸提取-ICP-MS氦气碰撞模式测定地球化学样品中V、Cr、Ni、Ge、As,简化了分析流程,样品消解时间仅2 h,相比于高压密封方法(消解时间48 h)具有消解快速、多元素同时测定、检出限低的特点。

     

    Abstract: A microwave digestion method to simultaneously determine V, Cr, Ni, Ge and As in geochemical samples by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is proposed. There are two main factors to influence the method accuracy: Cr and Ni released from stainless bomb could contaminate the samples by high press digestion and volatile elements, such as Ge and As, lost during pretreatment, and polyatomic molecular ions have mass influence on the determination by ICP-MS. In order to eliminate these two kinds of influences, four kinds of digestion methods were compared, including microwave digestion with nitric acid/aqua regia extraction and high pressure digestion with nitric acid/aqua regia extraction. The method by microwave digestion instead of high pressure digestion avoids the problem of contamination of Cr and Ni and loss of Ge and As with short digestion times. The nitric acid extraction, avoiding the addition of Cl-, has better analysis effect when compared with aqua regia extraction. A helium dilution technique based on the octopole reaction system ICP-MS was applied to decrease the interference of polyatomic molecular ions, such as 37Cl14N interference on 51V, 35Cl16OH interference on 52Cr, 35Cl37Cl interference on 72Ge and 40Ar35Cl interference on 75As. Based on the study of rock, stream sediments and soil national standard material by ICP-MS combined with nitric acid extraction, the results showed that the detection limits of V, Cr, Ni, Ge, and As by the proposed method were 1.09 μg/g, 0.19 μg/g, 0.55 μg/g, 0.02 μg/g and 0.50 μg/g, respectively. The RSDs were less than 4%. The detection limits of V, Cr and Ni by high pressure digestion were 3.48 μg/g, 13.09 μg/g and 21.67 μg/g, respectively. The proposed method was simple, time-saving (from 48 h to 2 h) and has the capability of simultaneous determination of multielements with low detection limits.

     

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