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

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.