Non‐specific retention characteristics of dissolved β‐cyclodextrin derivatives in open tubular column gas chromatography

The solvation parameter model is used to identify contributions from intermolecular interactions responsible for non-specific retention in gas chromatography for three dissolved p-cyclodextrin derivatives in a poly(cyanopropylphenyldimethylsiloxane) stationary phase. The cyclodextrins are permethylated p-cyclodextrin (Cyclodex-B), heptakis(2,3-di-O-methyl-6-O-t-butyldimethylsilyl)-β-cyclodextrin (CycloSil-B) and heptakis(2,3-di-O-acetoxy-6-O-t-butyldimethylsilyl)-β-cyclodextrin (Rt-βDEXsa). Taking DB-1701 as a reference phase for the poly(cyanopropylphenyldimethylsiloxane) solvent, it is shown that the dominant interactions for the cyclodextrin derivatives are associated with their hydrogen-bond basicity and capacity for dipole-type interactions. None of the cyclodextrin derivatives are hydrogen-bond acids and all are weakly electron lone pair repulsive. The cohesive properties of the dissolved phases are similar to those of the solvent, except for Rt-βDEXsa, which is significantly more cohesive. Also, Rt-βDEXsa shows significant inclusion complexation for the compounds used to determine the system constants of the solvation parameter model resulting in poor statistical models, suitable only for qualitative interpretation. The Cyclodex-B and CycloSil-B columns are compared to a database of 23 open-tubular column stationary phases possessing similar selectivity to each other but different selectivity for non-specific interactions to the other stationary phase types.