Department of Lithospheric Research, University of Vienna, Vienna, 1090, Austria.
Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budapest, 1112, Hungary.
Rapid Commun Mass Spectrom. 2021 Jun 15;35(11):e9081. doi: 10.1002/rcm.9081.
Complete decomposition of silicate rock matrices is crucial in determining their isotopic compositions, but acid dissolution in a high-pressure steel-jacketed bomb, which has been the only powerful, effective technique thus far, is time-consuming and expensive. Rock dissolution using ammonium bifluoride (ABF), as described here, is a viable alternative.
Geological reference materials (GRMs) were digested using ABF in closed Teflon beakers at temperatures of 220/230°C in a convection oven and subsequently treated with HNO . Hf-Sr-Nd were separated and purified using ion-exchange chemistry columns calibrated for 50-2 mg samples. The isotopic compositions of Sr-Nd were measured by Thermal Ionization Mass Spectrometry, while that of Hf by Multi-Collector Inductively Coupled Plasma Mass Spectrometry, both with normal 10 Ω and gain calibrated 10 Ω amplifiers.
Total procedural blanks of our protocol are 0.5 ng for Sr, 0.2 ng for Nd and <25 pg for Hf. Test runs with GRMs, ranging in composition from basic to felsic and dissolved in ABF, yield accurate Sr/ Sr, Nd/ Nd and Hf/ Hf isotope ratios as compared with those obtained with the bomb dissolution technique. Reproducibilities were comparable, on the order of 10-20 ppm. Our technique allows combined Hf-Sr-Nd isotope analyses of low-mass (50-2 mg) samples.
The ABF digestion is an alternative technique to high-pressure bomb dissolution in matrix decomposition for accurate and reproducible Hf-Nd-Sr isotope analyses of geological samples within a reasonable time (3-4 days), with high sample throughput and low costs in geochemistry and environmental sciences.
彻底分解硅酸盐岩石基质对于确定其同位素组成至关重要，但迄今为止，唯一强大有效的技术是在高压钢套炸弹中进行酸溶解，这种方法既耗时又昂贵。本文所述的使用氟化氢铵（ABF）溶解岩石是一种可行的替代方法。
地质标准物质（GRMs）在 220/230°C 的对流烘箱中使用 ABF 在封闭的聚四氟乙烯烧杯中进行消化，并随后用 HNO 处理。使用离子交换化学柱分离和纯化 Hf-Sr-Nd，该柱经过 50-2 mg 样品校准。Sr-Nd 的同位素组成通过热电离质谱法测量，而 Hf 的同位素组成通过多收集电感耦合等离子体质谱法测量，两者均使用标准 10 Ω 和增益校准 10 Ω 放大器。
我们方案的总程序空白分别为 Sr 的 0.5 ng、Nd 的 0.2 ng 和 Hf 的 <25 pg。用 ABF 溶解的从基性到长英质组成的 GRMs 进行的测试运行，与炸弹溶解技术相比，可得到准确的 Sr/ Sr、Nd/ Nd 和 Hf/ Hf 同位素比值。重现性相当，约为 10-20 ppm。我们的技术允许对低质量（50-2 mg）样品进行 Hf-Sr-Nd 同位素联合分析。
ABF 消化是一种替代高压炸弹溶解的技术，可用于地质样品中准确和可重现的 Hf-Nd-Sr 同位素分析，在合理的时间（3-4 天）内具有较高的样品通量和较低的地球化学和环境科学成本。
