Headspace gas analysis: the role and the design of concentration traps specifically suitable for capillary gas chromatography

Abstract

The wealth of recommended headspace techniques causes almost overwhelming evaluation problems. Some techniques work perfectly, and could hardly be improved upon. Many others suffer from their origin; they were developed for use with packed columns and have been improperly adapted to capillary gas chromatography. The critical point is the lack of conformity, particularly in terms of gas flow-rates, of the traditional concentration traps with the requirements of capillary columns. Important advantages (simpler technique, increased quantitative reliability) are gained with narrow-bore and open-tubular traps that permit instantaneous thermal desorption. Two types of such traps, both showing the dimensions of a piece of capillary column are presented and tested. The first type contains charcoal particles melted into the glass surface. Of particular importance, far smaller charcoal particles can be used than for packings. The second type contains extremely thick (12–15 μm) coatings of stationary phase. Some examples of applications show the present state of development. Intensive further development is necessary to provide the basis for a complete evaluation.