Copper-Phthalocyanine Stationary Phases (Cu-PCS) for Fullerenes Separation in Microcolumn Liquid Chromatography

Three copper-phthalocyanine stationary phases (Cu-PCS) were evaluated for fullerenes separation with microcolumn liquid chromatography. These phases offer two dominant interactions between fullerenes and the bonded moiety, solvophobic interaction, and π-π interaction. The former can be induced by the alkyl chains which are attached to the silica surface by the endcapping process, and the latter is the main target of these phases which should be induced by the phthalocyanine moiety. The different alkyl chain length of the endcapping agents such as ethanoyl, butyryl(butanoyl) and decanoyl made a big difference in performance for fullerenes separation, because longer chains disturb the direct π-π interaction between fullerenes and the phthalocyanine moiety, and induce smaller capability of molecular size and shape recognition. However, the appropriate alkyl chain length induces a higher possibility of the interaction between the solutes and phthalocyanine moiety because the chains can move to catch fullerenes on the phthalocyanine moiety. Temperature effect on retention reveals much clearer sight of the retention mechanism, since these phases produce unusual temperature dependency on retention where the retention and separation performance for fullerenes is enhanced with increasing temperature.