Abstract: Boron(B) isotope analysis is an important tool in the research of earth and planetary science. However, challenges still exist for precise and accurate measurements of boron isotope ratios of silicate material due to the challenges in sample digestion.
Alkaline fusion is a suitable sample dissolution method for boron isotope analysis in silicates. At present, alkaline fusion  methods require expensive platinum or glassy carbon crucibles as well as high flux-to-sample ratios. Additionally, the existing methods used for dissolving the fusion cake may cause boron loss. To achieve full dissolution and effectively prevent B loss, this study reports an improved alkali fusion method using sodium hydroxide and silver crucibles with a low flux-to-sample mass ratio of 5:1. Full dissolution was achieved through gentle heating in the presence of water combined with a stepwise dissolution procedure, which effectively prevented B loss during the dissolution of the fused alkaline cake. Using this improved procedure for dissolution, Amberlite IRA743 B-specific resin for B purification, and a multi-collector inductively coupled plasma mass spectrometer (MCICP- MS) for isotope analysis, we report boron isotope compositions and concentrations data for five silicate international standards. The results are consistent with the published data within analytical uncertainties. This safe and efficient method will greatly facilitate B isotope research of silicates.

Key words: boron isotope, alkaline fusion, ion-exchange chromatography, MC-ICP-MS