混合酸比例对ICP-MS/OES测定地球化学样品中多元素的影响

The Effect of Mixed Acid Ratio on the Determination of Multielements in Geochemical Samples by ICP-MS/OES

应用电感耦合等离子体质谱/发射光谱仪(ICP-MS/OES)测定地球化学样品中的多元素时,通常采用混合酸(盐酸-硝酸-氢氟酸-高氯酸)分解试样,但不同比例的混合酸对试样的分解效果影响极大,导致测试结果中经常出现铬、锰、铁、铝、钛及部分稀土元素测定结果偏低、精密度不理想的情况。本文通过改变混合酸中各类酸的混合比例,采用逆王水-氢氟酸-高氯酸分解试样,逆王水提取,使上述元素获得了较为理想的分解效果,特别是这些元素含量较高的样品分解效果的改善尤为显著。实验证明:当取样量为0.100 g时,采用8 mL逆王水、6 mL氢氟酸、3 mL高氯酸分解试样,8 mL逆王水提取,用国家一级标准物质进行验证,测试结果的相对标准偏差(n=6)为0.34%~4.02%,本方法精密度和准确度均满足地质实验室质量管理规范要求,可快速、准确、批量测定地球化学样品中的多元素。

When determining elements in geochemical samples,the sample is usually decomposed by mixed acid( hydrochloric acid-hydrofluoric acid-perchloric acid) by Inductively Coupled Plasma-Mass Spectrometry( ICP-MS)and Inductively Coupled Plasma-Optical Emission Spectrometry( ICP-OES). However,the different proportions of mixed acid have a great influence on sample decomposition,resulting in lower analytical results of chromium,manganese,iron,aluminum,titanium and parts of rare earth elements,and bad analytical precision. In this study,samples are digested by mixed solution of inverse aqua regia,hydrofluoric acid,and perchloric acid,and then extracted by inverse aqua regia. This improves the decomposition of the above elements,especially for samples with high contents of these elements. Results show that the relative standard deviation( n = 6) ranges from 0. 34% to 4. 02% for repeated determination of national level standard materials when 0. 1 g sample was digested by 8 mL inverse aqua regia,6 mL hydrofluoric acid,and 3 mL perchloric acid,and then extracted by 8 mL inverse aqua regia. The accuracy and precision of this method can satisfy the quality control standard requirements of the geology laboratory. This method establishes a fast and accurate approach to batch determination of multielements in geochemical samples.