Analytical Sciences

Effects of Trimethylsilylation of Copper(II)-Phthalocyanine Sulfonyl-Aminopropyl Silica Gels on the Separation of pi-Electron-Rich Compounds by High-Performance Liquid Chromatography

Akimasa IWADO,*¹ Masaki MIFUNE,*²  Yoshihiro MORI,*¹ Midori ONODA,*¹ Takemine KANAI,*¹ Noriko MOTOHASHI,*³ Jun HAGINAKA,*⁴ and Yutaka SAITO*²

*1 The Graduate School of Natural Science and Technology, Okayama University, Tsushima-Naka, Okayama 700-0072, Japan
*2 Faculty of Pharmaceutical Sciences, Okayama University, Tsushima-Naka, Okayama 700-8530, Japan
*3 Kobe Pharmaceutical University, Motoyamakita-Machi, Higashinada, Kobe 658-0003, Japan
*4 Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Koshien, Nishinomiya 663-8179, Japan

As an attempt to elucidate the factor(s) responsible for the poor performance of a copper(II)-phthalocyanine aminopropyl-silica gels (Cu-PCS_D) column for HPLC, the silanol and/or amino groups remaining on Cu-PCS_D were endcapped with trimethylchlorosilane (TMCS) or N-trimethylsilylimidazole (TMSI). The trimethylsilylated Cu-PCS_Ds (Cu-PCS_D-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 anthracene and pyrene. As a result, trimethylsilylation with TMSI, which reacts only with silanol-groups, was not effective to improve the column efficiency. 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-PCS_D column, indicating that the low N values on the Cu-PCS_D column were caused by electrostatic interactions between PAHs and the remaining amino-groups on Cu-PCS_D. Furthermore, the retention data of mutagenic heterocyclic amines (HCAs) indicated that the remaining amino groups interact with the polar groups of HCAs.

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