“Simultaneous determination of some water soluble vitamins in multivitamin preparations by high performance liquid chromatography”.

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A High Performance Liquid Chromatographic method was developed to assay some water -soluble vitamins (nicofinamide, pyridoxine, riboflavin and folic acid) in multicomponent pharmaceutical formulations. The method involved the use of sodium dihydrogen orthophosphate buffer solution adjusted to pH 4.0 using acetic acid. Chromatographic conditions of (-24 reverse-phase column, 15cm x 4.6mm i.d., flow rate of 1.5m1/min. and an injection volume of 20μl at a detection wavelength of 254nm. The mode of operation is isocratic and was performed at room temperature requiring about 10 minutes of elution time. The calibration curves obtained indicated linearity of peak area with concentration of vitamins over a range of 50-500μg/ml for folic acid. 5-500μg/l for nicotinamide and 50 - 500μg/ml for pyridoxine Quantitation of the vitamins in commercial preparations were accomplished using peak area ratio with external reference standard of the specified vitamins. Stability of the vitamins in the mobile phase was determined in the presence of para –N, N-dimethyl aminobenzaldehyde as an internal standard. Riboflavin was found to enhance the oxidative degradation of folic acid in a mixture of the two vitamins at pH 4.0. The results of the HPLC method were found to be specific in qualitative determination of the vitamins with retention times of 1.45 for pyridoxine. 1 .76 for nicotinamide. 3.50 for riboflavin. 4.5 for aminobenzaldehyde and .0 for folic acid. The method was also found to be accurate and precise with percentage mean of label recovery o 95 .00% - 102.00% and a relative standard error of the mean of less than 1 0% for between and within runs. Comparison of the HPLC method with UV spectrophtometric method reveals that the mean percentage claim of the HPLC method is between 99.43% - 1 01 .80% and standard deviation of 0.44 - 0.82. it is 103.70 - I 08.30 with standard deviation of 1 .42 – 6.99 for UV method indicating the lack of accuracy and precision on the part of UV spectrophotometric method. The method developed could he the required analytical technique for ascertaining the quality and quantity of vitamins in multivitamin preparations.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science, 1999