Carrier gas as a new factor influencing the selectivity of the gas–stationary liquid phase chromatographic system

This paper generalizes studies on the influence of carrier gas on relative and absolute retention values. This line of research is also of importance due to the fact that, in the opinion of many chromatographers, the role of the carrier gas is limited only to transporting analyzed compounds along the column. However, even under conditions of the conventional capillary gas–liquid chromatography (i.e. at column pressures under 5 atm) carrier gas (its nature and pressure) significantly influences retention and separation of the analyzed compounds. First, carrier gas (N2 and CO2, for example) dramatically affects relative retention values. For this reason, one should use limit values of αij(0)=lim αij(Pav) and Ii(0)=lim Ii(Pav) Ii(0)=limIi(Pav) with Pav→0 as chromatographic constants, rather than traditional relative retention values αij(Pav) and Ii(Pav). Second, the average pressure Pav of the carrier gas in a column and the nature of the carrier gas influence the selectivity of the gas–stationary liquid phase chromatographic system. Third, wishing to maximize the role of the carrier gas as a factor that improves separation of analyzed compounds, we should design a special gas chromatograph that would allow work with pressures in the column up to 30–50 atm.