LAUSR

Abstract Various refractory samples of boron such as titanium borides, rare earth borides, boron carbides having natural and non-natural isotopic composition were analysed by thermal ionization mass spectrometry as Na2BO2+ ions. Samples were fused with Na2CO3 directly on the filament after adjusting the B/Na mole ratio to 2 and in certain cases modifications in the loading technique were required to obtain precise 10B/11B isotopic ratio. A few of the samples expected to have natural 10B/11B ratio were observed to be slightly enriched in 10B. Dissolved samples as well as boron purified by extraction with 5% 2-Ethyl Hexane Diol(EHD) were analysed for 10B/11B ratio to ascertain the accuracy of the results obtained by the direct fusion method. Precision of about 0.02% (1RSD) was obtained for 10B/11B isotopic ratio measured in all the three types of samples. A good agreement of the dissolved sample and purified boron fraction with the directly fused sample validated the direct fusion method as a fast and reliable technique for isotopic analysis of boron in refractory samples.