Effect of etching with gaseous hydrogen chloride on the quality of glass capillary columns

Abstract The effect of etching with gaseous HCl on the quality of glass capillary columns made of soft soda-lime glass and coated with OV-101 and Carbowax 20M has been studied. The quality of the columns was evaluated in terms of the number of theoretical plates, coating efficiency and Kovats retention indices of polychlorinated biphenyls (PCBs). The retention indices depend, inter alia , on the time and temperature of etching of the inner walls of the capillary. Columns coated with a thin film of OV-101 show adsorption properties resulting in an increase in Kovats retention indices and are capable of separating pairs of PCBs which, when chromatographed on columns coated with a thicker film of stationary phase, remain unresolved. It has been found that by coupling shorter columns together, extremely efficient columns or columns of required polarity can be prepared.