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Total Rock Dissolution Using Ammonium Bifluoride (NH4HF2) in Screw-Top Teflon Vials: A New Development in Open-Vessel Digestion

Complete sample digestion is a prerequisite for achieving reproducible and accurate analytical results for geological samples. Open-vessel acid digestions successfully dissolve mafic samples, but this method cannot achieve complete dissolution of felsic samples, because of the presence of refractory minerals such as zircon. In this study, an efficient and simplified digestion technique using the solid compound NH4HF2 in a screw-top vial has been developed for multielement analysis of different types of rock samples. NH4HF2 has a higher boiling point (239.5 °C) than conventional acids such as HF, HNO3 and HCl, which allows for an elevated digestion temperature in open vessels, enabling the decomposition of refractory phases. Similar to HF, HNO3 and HCl, ultrapure NH4HF2 can be produced using a conventional PFA sub-boiling (heating and cooling) purification system. A digestion time of 2–3 h for 200 mg NH4HF2 in a Savillex Teflon vial at 230 °C is sufficient to digest 50 mg of the felsic rock GSP-2, which is...

Authors:   Wen Zhang; Zhaochu Hu; Yongsheng Liu; Haihong Chen; Shan Gao; Richard M. Gaschnig
Journal:   Analytical Chemistry
Year:   2012
DOI:   10.1021/ac302327g
Publication date:   05-Dec-2012
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