Sandwiched columns in gas—liquid chromatography

Abstract

Sandwiched capillary columns consisting of one or more carbon threads inserted in a glass capillary and coated with a stationary phase have been prepared and the dependence of the performance characteristics on the capillary diameter and on the number of carbon threads has been investigated. Van Demeter equation constants, gas and liquid phase mass transfer resistance terms, performacne indices and performance parameters have been calculated. A comparison between sandwiched columns and other types of columns that regarding permeability, performance index, performance parameter and loading capacity, the former have intermediate values between open tubular and clasical packed columns. The advantage of the sandwiched columns with respect to packed capillary columns lies in the ease of their preparation and the lower pressure drop corresponding to a minimum plate height. Large columns with more than a hundred threads offer no advantage over classical packed columns.