Separation performance of the calix[8]arene functionalized with polyethylene glycol units for capillary gas chromatography

In this paper, an amphiphilic calix[8]arene with polyethylene glycol unit branches (C8A-PEG) was synthesized and applied for capillary gas chromatography (GC). The C8A-PEG was coated on the inner wall of a capillary column by a static method with the column efficiency of 3165 plates/m and polar nature. As demonstrated, the C8A-PEG column has excellent physicochemical properties and separation performance since it has π -electron-rich 3D cavity which combines with polar PEG units. Compared with two columns corresponding to the construction units C8A and PEG, the C8A-PEG column shows distinctly advantageous performance for the mixture of 22 components with diverse types. Impressively, it shows satisfactory resolution for positional isomers and cis -/ trans - isomers, especially the challenging isomers of toluidine and dimethylaniline. The outstanding distinguishing capability of the C8A-PEG stationary phase is mainly attributed to the abundant molecular recognition interactions, including van der Waals, dipole–dipole, H-bonding and π – π stacking interactions. This work has proved that the new GC stationary phases constructed by different units can complement each other's advantages, improve their physicochemical properties and separation performance, and have broad application prospects in chromatographic analysis. Graphical abstract