Dependence of the efficiency of a capillary column in gas chromatography on the relative pressure of the carrier gas

The effect of relative pressure on the efficiency of an open capillary column in gas chromatography was studied. It was shown that the relative pressure was not the only parameter determining the column efficiency. The pressure drop in the column is an additional parameter. At high values of relative pressure, the pressure drop in the column becomes determining for the column efficiency. The smallest value of a height equivalent to a theoretical plate (HETP) is achieved at the minimum values of the pressure drop and the relative pressure, which is accompanied by a decrease in the optimal flow rate of the carrier gas and an increase in the time of determination. The maximum improvement in the column efficiency is determined by the column properties and can exceed 12.5%, that is, the value predicted by Cramers for open capillary columns.