MEASUREMENT OF ISOTOPE RATIOS OF BORON AN D SILICON BY GLOW-DISCHARGEMASS-SPECTROMETRY USING A SMALL QUANTITY OF SAMPLE

Glow discharge mass spectrometric (GDMS) analysis of isotopic composit ions of pure boron and silicon has been studied by using a VG9000 inst rument and a small quantity sample. A disk sample was prepared by pres surizing the mixture of metallic boron (or silicon) and 1.0 g of galli um with 39 MPa (400 kg/cm(2)). Optimum ratio of mixing of the sample a nd the gallium binder was examined. Increasing the sample content of t he mixture caused a counting error due to the dead time of a Daly dete ctor, which was estimated to be 0.014 mu s for an integration time of 200 ms. Observed isotopic compositions of metallic boron powder and si licon thin film showed good agreement with the natural abundance or es timated values. The relative standard deviation (RSD) of repetitive fi ve measurements was less than 0.5% for the analytical values of the is otopic compositions.