DEPENDENCE OF THE RELATIVE RETENTION OF ORGANIC-COMPOUNDS ON THE NATURE AND PRESSURE OF THE CARRIER GAS AND ON THE THICKNESS OF THE PEG-20MFILM IN THE CAPILLARY COLUMN

The effects of the carrier gas nature and pressure on the relative ret ention values of organic compounds were studied using a series of capi llary columns differing in the film thickness of the polar stationary phase (PEG-20M). Relative retention depends linearly on the carrier ga s pressure. This dependence becomes more pronounced in the following o rder of carrier gases: helium < nitrogen < carbon dioxide. The limitin g relative retention at a carrier gas pressure approaching zero rather than relative retention values measured experimentally (relative rete ntion time, Kovats retention index, etc.) is an invariant characterist ic of a compound subjected to chromatography. For the carrier gases st udied, the limiting retention value almost does not depend on the natu re of the carrier gas used. The limiting retention values depend on th e thickness of the stationary liquid phase PEG-20M film, indicating th e complex absorption-adsorption nature of these parameter. Dissolution of a carrier gas in the stationary liquid phase has an effect on the relative retention.