HIGH-ACCURACY ASSAY OF SUB PPM TRACES OF SILICON BY ISOTOPE-DILUTION MASS-SPECTROMETRY

Thermal ionization mass spectrometry of silicon has been developed enabling high accuracy assay of Si by isotope dilution mass spectrometry (ID-MS). The method works with silicon in the form of sodium silicate and uses barium hydroxide to enhance ionization. In the process a Si-29 spike reference material was established. The new method was tested on water samples doped with 15 ppb of silicon and it was shown that ppb traces of silicon in water can be assayed to better than 10% accuracy (total uncertainty).