ABSTRACT
In this paper, carbon nanotubes (CNTs) were added into chitosan (CS) hydrogels in the form of chitosan modified CNTs (CS-CNTs) composites to prepare carbon nanotubes hydrogels (CNTs-GEL). The products, named CS-MWCNTs, were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. Swelling properties and effect of pH on controlled release performance of the two kinds of hydrogels, CNTs- GEL and pure chitosan hydrogels without CNTs (GEL), were investigated respectively. The results showed that CNTs-GEL possess better controlled release performance than GEL. The releasing equilibrium time of CNTs-GEL was longer than that of GEL in both pH = w7.4 and pH=1.2 conditions, although the release ratios of the model drug are similar in the same pH buffer solutions. It is found that release kinetics is better fitted Ritger-Peppas empirical model indicating a fick-diffusion process in pH = 1.2, while in pH = 7.4 it was non-fick diffusion involving surface diffusion and corrosion diffusion processes.
ABSTRACT
The resolution of clenbuterol hydrochloride enantiomers was achieved by thin-layer chromatography on silica gel GF254 plates impregnated w ith beta-cyclodextrin. The effect of stereoselective auxiliary (acetonitrile and alcohol) was investigated. Resolution of clenbuterol hydrochloride enantiomers could be attained by using alcohols of butanol, 2-butanol or tert-butanol together with acetonitrile as developing solvent. The optimal conditions of resolution were determined as follows: a plate prepared with 15.00 g silica gel GF254 impregnated with 1.00 g beta-cyclodextrin, acetonitrile-2-butanol (20:80, v/v) as developing solvent and developed at room temperature. Under these conditions, Rf of the two isomers of clenbuterol hydrochloride enantiomers were 0.34 and 0.72 respectively. The resolution was 4.09 with baseline separation and the spots in chromatogram were almost of the same size.