Isotopic analysis of boron in boron trifluoride by mass spectrometry, and measurement of natural boron 10 concentration

A conventional mass spectrometer is used for precise measurements of the isotope ratios of boron in boron trifluoride samples with widely differing concentrations of boron 10. "Memory" effects caused by the adsorption of boron trifluoride on to the surfaces of the inlet system have been investigated, and it is found that these can be reduced to a workable level by careful design of the inlet system. By blending together enriched and depleted boron trifluoride, standard samples with known isotopic constitutions are prepared and used to calibrate the mass spectrometer. The true and measured isotope ratios are thus found to differ by several per cent, an effect attributed to mass discriminations in the ion source. After correcting for this error, the boron 10 atomic concentration in some naturally-occurring boron is found to be 19.27 ± 0.13%.