Column preparation for reversed-phase high-temperature open tubular column liquid chromatography

Abstract

A method for the preparation of stable reversed-phase columns for high temperature open tubular column liquid chromatography (HT-OT-LC) has been developed and the effect of covalent bonding of the stationary phase to a covalently bonded deactivation layer, as well as, crosslinking of the polysiloxane stationary phase has been investigated. It was found that the column lifetime depended primarily on the extent of crosslinking of the stationary phase film with azo- tert.-butane and a dynamic crosslinking procedure was developed for this purpose. By extensive crosslinking of the polysiloxane stationary phase, column lifetimes of more than several hundreds of hours could be obtained at 150°C. Inadequate crosslinking, on the other hand, resulted in shorter column lifetimes most likely as a result of hydrolysis of the stationary phase polymer leading to its collapse in the centre of the column. No significant difference in column lifetime was seen between columns prepared with 50% n-octylpolymethylsiloxane or 49% n-octyl-, 1% n-octenylpolymethylsiloxane stationary phases, with cyano or octyl groups in the deactivation layer, or between columns with different stationary phase film thickness (in the range between 0.25 and 0.60 μm).