Vitamins are essential components for maintaining physiological functions in living bodies. In particular, five water-soluble essential vitamins, B1, B2, C, nicotinic acid and nicotinamide are sometimes lacking in human bodies. The necessary quantities of three water-soluble vitamins, B6, B12 and folic acid have been determined by the NRC (National Research Council), though these vitamins are seldom lacking in human bodies. This chromatogram shows an example of the analysis of such water-soluble vitamins except folic acid. This analysis has been performed by reversed phase mode with gradient elution. Good calibration curves are obtained for the vitamins using RSpak DE-413 (a column for reversed phase chromatography). As an example, calibration curves for vitamin B2 and vitamin B6 are shown below.