A system map for the ionic liquid stationary phase 1,12-di(tripropylphosphonium)dodecane bis(trifluoromethylsulfonyl)imide for gas chromatography

The solvation parameter model is used to prepare a system map for the retention of volatile organic compounds on the ionic liquid stationary phase 1,12-di(tripropylphosphonium)dodecane bis(trifluoromethylsulfonyl)imide (SLB-IL60) by gas chromatography over the temperature range 80-280 °C. Retention is governed by dispersion, dipole-type and hydrogen-bonding interactions with a different temperature dependence. The hydrogen-bond acidity of the SLB-IL60 column is unexpected since the stationary phase contains no hydrogen-bond acid groups and is not obviously connected to contributions from the deactivated column wall. The polarity number is shown to be a poor indicator of column retention properties. Principal component analysis with the system constants of the solvation parameter model as variables indicates that the properties of SLB-IL60 are not duplicated by any of the common poly(siloxane) and poly(ethylene glycol) stationary phase chemistries in common use for column preparation. The SLB-IL60 column has similar selectivity to a poly(cyanopropylphenyldimethylsiloxane) stationary phase containing 50% cyanopropylphenyl siloxane monomer but the two columns are not selectivity equivalent. Poly(ethylene glycol) stationary phases indicated as most similar to SLB-IL60 based on their polarity numbers are shown to have quite different selectivity.