PEEK columns for open-tubular liquid chromatography with electroosmotic flow

A surface treatment method was developed for bonding a hydrophobic layer on the inner surface of poly(ether ether ketone) (PEEK) capillaries for electroosmotically driven open-tubular liquid chromatography (LC). The inner wall of the PEEK capillaries was treated with a dilute chlorosulfonic acid solution. This treatment increased the column surface area and thus improved the phase ratio and, at the same time, activated the surface for the subsequent reaction with alkylamines. Capillary columns prepared in this manner showed retention characteristics similar to reversed-phase LC. The column performance was evaluated using neutral compounds as analytes; with a 65-μm-inside-diameter capillary, separation efficiencies were 4.77×104 plates/m for an unretained solute, but those for retained solutes were lower.