Effects of trimethylsilylation of copper(II)-phthalocyanine sulfonyl-aminopropyl silica gels on the separation of pi-electron-rich compounds by high-performance liquid chromatography

As an attempt to elucidate the factor(s) responsible for the poor performan ce of a copper(II)-phthalocyanine aminopropyl silica gels (Cu-PCSD) column for HPLC, the silanol and/or amino groups remaining on Cu-PCSD were endcapp ed with trimethylchlorosilane (TMCS) or N-trimethylsilylimidazole (TMSI). T he trimethylsilylated Cu-PCS(D)s (Cu-PCSD-TMCS and -TMSI) were investigated concerning their performance as an HPLC-stationary phase in the separation of pi -electron-rich polyaromatic hydrocarbons (PAHs), such as mutagenic a nthracene and pyrene. As a result, trimethylsilylation with TMSI, which rea cts only with silanol-groups, was not effective to improve the column effic iency. In contrast, trimethylsilylation by TMCS, which reacts with both the silanol- and amino-groups, improved the theoretical plate numbers (N) for PAHs separation with the Cu-PCSD column, indicating that the low N values o n the Cu-PCSD column were caused by electrostatic interactions between PAHs and the remaining amino-groups on Cu-PCSD. Furthermore, the retention data of mutagenic heterocyclic amines (HCAs) indicated that the remaining amino groups interact with the polar groups of HCAs.