Effect of high-temperature ageing on the gas chromatographic properties of porous polymer beads

Abstract

The effect of column ageing at 200δC under a flow of carrier gas on the gas chromatographic behaviour of porous polymer bead (PPB) stationary phases was investigated by analysing standard mixtures of linear alkanes and polarity “probes”: ethanol, butanol, pyridine, nitromethane, l-nitropropane, benzene, methylethyl ketone and methylpropyl ketones. A linear dependence of the logarithm of the adjusted retention times (log t′ R on the time of ageing was observed for many PPBs, but some of them showed non-linear relationships (Chromosorb 103, 107 and 108). The PPBs showing linear behaviour can be divided into four classes: (1) no variation of log t′ R with ageing (Porapak N, Q and R and Chromosorb 106); (2) linear increase in log t′ R (Porapak P and S and Chromosorb 101, 102 and 104); (3) linear decrease in log t′ R (Porapak T); (4) horizontal, increasing or decreasing log t′ R values depending on the chemical composition of the polarity probes (Chromosorb 105). The variation of retention times and elution order with thermal ageing of the PPBs can explain the differences between retention data reported in the literature and must be taken into account in the determination of the high-temperature polarity of these stationary phases.