Abstract: A RP-HPLC gradient elution method was developed for the simultaneous determination of eight water-soluble vitamins, including ascorbic acid, thiamine, riboflavin, nicotinic acid, pyridoxine, cyanocobalamin, folic acid and nicotinamide in fruit vinegar. The effects of temperature, buffer solution concentration, pH value and gradient elution procedure on chromatographic separation were studied. The mobile phase was a mixture of 0.1 mol/L sodium acetate solution (pH 4.25) and methanol at a flow rate of 1.00 mL/min. The column temperature was set as 30 ℃. Baseline separation was achieved for 8 water-soluble vitamins within 14.2 min. The detection was carried out at 266 nm and 280 nm. The method offered excellent linearity over a range of 0.05－12.5 μg/mL for riboflavin and folic acid, 0.1－25 μg/mL for ascorbic acid, thiamine, nicotinic acid and nicotinamide, 0.15－37.5 μg/mL for pyridoxine and cyanocobalamin, with correlation coefficients (r＞0.999). The detection limits were in the range of 0.47－3.46 ng/mL This method has been successfully applied to assay vitamins in fruit vinegar. The average spike recovery varied from 92.4% to 105.2% with RSD in the range of 0.08%－1.54% (n =3).

Key words: RP-HPLC, water-soluble vitamins, fruit vinegar