Photo-responsive retention behavior of azobenzene-modified cyclodextrin stationary phase in micro-HPLC

An azobenzene-modified gamma -cyclodextrin stationary phase (Az gamma -CDSP ) was prepared and its photo- and temperature responses for the retention o f perylene and pentacene were investigated using a mixture of methanol and water as the mobile phase in micro-HPLC. The retention of perylene slightly increased, whereas that of pentacene significantly decreased by UV light i rradiation to Az gamma -CDSP. These retentions recovered upon irradiation w ith visible light. Both retentions decreased upon an increase in the column temperature. It was presumed that the trans-azobenzene moiety acts as a pr eventive cap for perylene and a spacing for pentacene in filling the CD cav ity. An azobenzene-modified stationary phase changed its retention behavior with the column temperature and the light irradiation. An improvement in t he micro-HPLC system acid the optimization of the molecular structure of th e photo-responsive stationary phase would provide selective retention contr ol by the irradiation of light in micro-separation systems.