Reversed-phase capillary electrochromatography of aloins and related constituents of aloe

The separation of some anthrone-C-glucosyl constituents of aloe was carried out by isocratic capillary electrochromatography using a 50 mum I. D. colu mn packed with 3 mum ODS silica gel. In comparison to HPLC mode, CEC resolu tion of aloins was obtained in a very short time with a high selectivity fa ctor. The influence of mobile phase parameters (pH and ionic strength of th e buffer, acetonitrile amount in the eluent etc.) on the retention of aloin s was examined in order to improve the separation conditions and to study t he retention mechanism. Efficiency was found to increase with decreasing th e EOF up to a reduced plate height of about 2 at a reduced linear velocity of 0.3 mm s(-1). This effect was ascribed to the fact that, under the buffe r conditions used (pH 8), aloins are partially anionically charged, with a consequent low mass transfer between the mobile and stationary phases. Howe ver, resolution remains almost the same in a wide pH range permitting basel ine separations of aloins in short analysis times. Since aloins are known t o undergo fast degradation reaction dependent on pH, a kinetic study was al so carried out. The method was extended to the analysis of aloins in food a nd cosmetic products.