Abstract

The cause of precision problems arising when using non-eluting solvents for sample solutions in order to obtain a peak compression effect in low-dispersion liquid chromatography was investigated. Quantitative evidence was obtained to support the proposition that the problems were caused by adsorption of the analyte in the injection system. This phenomenon was quite marked when aqueous buffer was used to inject into organic-aqueous mobile phases and could still be significant when there was only a few percent difference in the organic content of the mobile phase and the less eluting injection solvent. While there was evidence for adsorption onto the inner walls of the stainless-steel tubing used for sample loops, it was clear that, for this case of liquid chromatography of indomethacin, adsorption onto Vespel rotor seals was the principal contributing factor to the effect.