Continuous mass spectrometric determination of 18O in hydrogen/water vapour gas mixtures

Mass spectrometry was used to monitor the decrease in 18O concentration in the gas phase when determining the oxygen tracer diffusion coefficient in a series of titanium oxides (TinO2n-1 with 3 ⩽ n ⩽ 8). To maintain constant oxide composition at temperature (1413 K), hydrogen/water vapour gas buffers were used; the continuous mass spectrometric determination of H218O in these buffers was achieved by operating the mass spectrometer dynamically at 433 K and monitoring the appropriate mass peaks. The precision in determining the H218O/H216O ratio was within 3%.