Dependence of the relative retention of organic compounds on the nature and pressure of the carrier gas and on the thickness of the PEG-20M film in the capillary column

The effects of the carrier gas nature and pressure on the relative retention values of organic compounds were studied using a series of capillary columns differing in the film thickness of the polar stationary phase (PEG-20M). Relative retention depends linearly on the carrier gas pressure. This dependence becomes more pronounced in the following order of carrier gases: helium < nitrogen < carbon dioxide. The limiting relative retention at a carrier gas pressure approaching zero rather than relative retention values measured experimentally (relative retention time, Kovats retention index, etc.) is an invariant characteristic of a compound subjected to chromatography. For the carrier gases studied, the limiting retention value almost does not depend on the nature of the carrier gas used. The limiting retention values depend on the thickness of the stationary liquid phase PEG-20M film, indicating the complex absorption-adsorption nature of these parameter. Dissolution of a carrier gas in the stationary liquid phase has an effect on the relative retention.