Direct chromatographic comparison of the relative adsorption activity of various types of capillary transfer tubing

The relative inertness of PTFE, polyether ether ketone (PEEK), nickel, stainless steel and deactivated fused silica for use as transfer tubing in gas chromatography was determined. These surfaces were compared by examining the apparent capacity factors for a wide variety of polar and non-polar substances. In all instances the capacity factors were based on the peak maximum time for the substance of interest relative to that of methane on the uncoated tubing. In general, as expected, deactivated fused silica was the least sorptive material, although for a few test solutes PTFE was superior. The results clearly show that neither PTFE nor PEEK tubing is inert for all solutes. A wide variety of peak shapes was observed; in some instances, a single species gave two peaks, indicating the complexity of the interactions taking place.