New Analytical Method for Measuring the Atomic Weight of Neon Using Gas Chromatography with a Thermal Conductivity Detector

The atomic weights of neon (Ne) gases were measured by gas chromatography with a thermal conductivity detector (GC-TCD). High-purity neon gas was used as the carrier and sample gases in this study, which is different from typical GC analysis. The peak signals from the GC-TCD appear when the thermal conductivity between the sample and carrier gases is different. In most gaseous molecules, the thermal conductivity has been assumed to be the same if the chemical species is the same. However, the thermal conductivity of neon gases shows different values among several manufacturers, because the relative abundance of the Ne-22 isotope, which is quite large (similar to 10% in atmospheric neon), varies due to the mass fractionation during air separation. We identified the atomic weights of seven neon gases. Additionally, the absolute isotope ratios of all neon gases were measured using a magnetic sector type gas/mass spectrometer. The atomic weights of the seven neon gases were compared with the results obtained from GC-TCD, and the results agreed with each other within the expanded uncertainty (k = 2).