Instrumentation and procedures
An HP3D CE system (Agilent, Waldbronn, Germany) equipped with a diode array spectrophotometric detector and uncoated fused-silica capillaries of 58.5 cm length (50 cm effective length) 75 mm id (375 mm o.d.) were used. New capillaries were successively flushed with 1 and 0.1 M NaOH and water at 60 C for 10 min each. Between runs, the capillary was flushed with 5 min BGE. Samples were injected hydrodynamically at 50 mbar 8 s. Separations were performed at 20 kV at 25 C. Detection was performed at 214 nm for all vitamins except for vitamin C that was 265 nm. Before injection, all solutions were filtered through 0.45 mm pore size nylon filters. CZE data acquisition was performed with ChemStation Software