Preparation of small-diameter capillary columns for gas and supercritical fluid chromatography

Abstract

Small diameter (25–100 μm I.D. fused-silica capillary columns with non-extractable SE-33, SE-54 and 50% phenyl polysiloxane stationary phases were prepared. Elevated coating temperatures and mixed solvent coating solutions facilitated the static coating of these small-diameter columns. Azo- tert.-butane was used as the free-radical initiator for crosslinking. Stationary phase film thicknesses of up to 1 μm were successfully immobilized. Coating efficiencies were above 70% (SE-33), 50–80% (SE-54), and 20–40% (50% phenyl polysiloxane). Nearly 700,000 theoretical plates (gas chromatography) were generated by a 46 m × 50 μm I.D. column coated with a 0.25-μm film of SE-54. In general, supercritical fluid chromatography efficiencies at practical mobile phase velocities were approximately one-fifth of those produced by gas chromatography at optimum mobile phase velocities from the same columns. Experimental determinations of column performance agreed well with theoretical predictions.