Sample preparation for geochemical analysis: Strategies and significance

Accurate determination of elemental and isotopic compositions of geological samples must be a pre-requisite for successful mineral exploration, basic geochemical and geochronological studies. During rock analysis, sample digestion which involves steps from simple dilution to partial or total digestions, is a crucial step and is the limiting factor many times for achieving reproducible and accurate analytical results. Sample preparation is a critical step in the geochemical analysis, and complete sample dissolution is a pre-requisite for obtaining accurate and precise data for geological materials in most studies. Sample matrix, analytes of interest, the analytical technique, and intended purpose play a major role in selecting the optimum sample preparation method. This review focuses on the recent advances, developments, and trends in sample digestion methods, such as open-vessel acid digestion, closed digestions, microwave digestion, alkali fusion, use of NH4F for both open and closed digestions, sintering with Na2O2, fire-assay methods, infrared radiation digestions, high-pressure asher digestions, and automated sample preparation systems (based on artificial intelligence) along with examples of some important and exciting applications in geochemical and geochronological studies. Various sample decomposition methods have been compared to bring out advantages and limitations for a particular application.