The effects of carrier gas viscosity on column efficiency in capillary gas chromatography

Abstract

The objective of this study is to determine the effects of carrier gas viscosity of hydrogen and helium on column efficiency; particularly when employing thin films. When using thin films, mass transfer in the stationary phase becomes negligible and mass transfer in the mobile phase predominates. It was envisioned that when employing thin films hydrogen would be the carrier gas of choice due to its higher diffusivity and lower viscosity. The combination of the previous factors should lead to faster analyses (isothermal) and higher column efficiency with hydrogen. Viscosity is the resistance of a liquid or gas to flow. The viscosity of a gas is determined by two factors: (1) the molecular weight of the gas; and (2) its temperature. When the temperature or molecular weight of the gas is increased its viscosity is also increased. In a chromatographic system, with a constant pressure drop, an increase in viscosity results in a decrease in the linear velocity of the carrier gas, ultimately resulting in lower column efficiency.