Abstract:

Objective  To explore the feasibility of quantitatively measuring the concentrations of vitamin  C (Vc) in         dark colour fruits and vegetables detected by  automatic potentiometric titration and high performance liquid chromatography (HPLC), and to provide experimental basis  for measurement  of Vc concentrations in  a few or amount of fruits and vegetables.Methods 15 kinds of fruits and 15 kinds of vegetables sold in supermarket were selected.After adding a small quantity of oxalic acid,these samples were crisped,filtered, and centrifuged sequentially,and then the concentrations of Vc in upper clean liquid were determined by automatic potentiometric titration and HPLC method.Accuracy and precision  test  for  the same sample were also done with two methods.Results There were no significant  differences between the detection results of Vc  concentrations detected   by  two  methods  (P>0.05), and the recovery  rates in red pepper detected with automatic potentiometric titration and HPLC methods were 98.34%-103.98%  and  99.66%-101.49%,respectively; the relative standard deviation (RSD)  were 1.77% -2.88%  and  0.15%-0.32%,respectively. The HPLC data had good linear relationship (R2 =0.999　9). Conclusion The two kinds of  test  methods are  ideal  methods for the determination of  Vc concentrations in dark colour  fruits and vegetables.They both have good accuracy and precision for the requirement of quantity analysis.

Key words: potentiometric titration;chromatography,high performance liquid, vitamin C, dark colour fruits and vegetables, accuracy, precision