Assessment of Dissolution of Silicate Rock Reference Materials with Ammonium Bifluoride and Nitric Acid in a Microwave Oven

Autor(es)

Magaldi, Thais T. ^[1] ; Navarro, Margareth S. ^[1] ; Enzweiler, Jacinta ^[1]

Afiliação do(s) autor(es)

^[1] Univ Campinas UNICAMP, Inst Geosci, Rua Carlos Gomes 250, BR-13108855 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: GEOSTANDARDS AND GEOANALYTICAL RESEARCH; v. 43, n. 1, p. 189-208, MAR 2019.
• Citações Web of Science: 4

Resumo

The complete dissolution of representative test portions of powdered rock samples for the determination of the mass fractions of trace elements by ICP-MS relies either on aggressive and time-consuming acid digestions or fusion/sintering with appropriate fluxes. Here, we evaluate a microwave oven dissolution method that employs a solution of NH4HF2 and HNO3. The entire procedure occurs in a closed vessel system and takes up to 4 h. In hundreds of digestions, the precipitation of fluorides was never observed. Replicate decomposition of 100 mg of twenty-one international reference materials (RMs) of igneous rocks, and also one of a shale presented mostly satisfactory recoveries of forty-one trace elements. Important exceptions were Zr and Hf in G-2 and GSP-2 (mean recoveries of ca. 70%), although for four other felsic rock RMs, the digestion was complete. For ultramafic rock RMs, we present Cr results that indicate quantitative dissolution of Cr-bearing phases. We discuss the findings and conclude that advances in sample preparation of geological materials for instrumental analysis would benefit from a better understanding of how specific characteristics, such as composition and crystallinity of certain minerals, may affect their reactivity. (AU)

• Processo FAPESP: 18/07317-3 - Geoanalysis 2018
• Beneficiário: Jacinta Enzweiler
• Modalidade de apoio: Auxílio à Pesquisa - Reunião - Exterior