Determination of eight water- and fat-soluble vitamins in multi-vitamin pharmaceutical formulations by high-performance liquid chromatography

In the present work, a reversed-phase high-performance liquid chromatograph ic procedure has been developed for the determination of water-soluble vita mins (thiamine hydrochloride, pyridoxine hydrochloride, nicotinamide, ribof lavin phosphoric ester and cyanocobalamine) and fat-soluble vitamins (retin ol palmitate, cholecalciferol, alpha-tocopherol acetate) in multi-vitamin p harmaceutical formulations. The sample treatment proposed consists of a sol id-phase extraction with C-18 AR cartridges that allow the separation of fa t-soluble vitamins, which were retained on the sorbent, from water-soluble vitamins. Afterwards, the water-soluble vitamins were analysed by HPLC on a Nova-Pack C-18 (150 x 3.9 mm, 4 mu m) analytical column, using CH3OH-0.05 M CH3COONH4 as mobile phase The chromatographic analysis of the fat-soluble vitamins was carried out after their sequential elution with methanol and chloroform from C-18 sorbent, on the above column. The mobile phase employe d was MeOH-CH3CN (95:5, v/v) working at a flow-rate of 2 ml min(-1) in isoc ratic mode. The solid-phase extraction for these vitamins had been previous ly optimised. The experimental variables studied were: application volume, elution solvents and cleaning solutions. The W-Vis detection of vitamins wa s made at 270 nm for all the water-soluble vitamins (362 nm for B-12) and 2 85 nm for the water-soluble and fat-soluble vitamins present in real sample s at different concentration levels. The accuracy of the method was tested obtaining an average recovery ranging between 78 and 116%. (C) 2000 Elsevie r Science BN. All rights reserved.