自动电位滴定法和高效液相色谱法测定深颜色果蔬中维生素C浓度的比较

Comparison of vitamin C concentrations in dark colour fruits and vegetables detected by automatic potentiometric titration and HPLC method

目的：探讨应用自动电位滴定法和高效液相色谱（HPLC）法定量测定深颜色果蔬中维生素C（Vc）浓度的可行性，为少量或批量果蔬样品Vc浓度的测定提供方法依据。方法：选取市售的15种蔬菜和15种水果的可食部分，加入一定量的草酸做Vc保护剂进行匀浆、过滤、离心处理，取一定量的上清液分别对其中的Vc浓度进行自动电位滴定和HPLC分析，对于同一红柿椒样品，分别用2种分析法对样品的Vc浓度进行准确度和精确度的测定。结果：2种分析法检测30种果蔬中Vc的浓度差异无统计学意义（P〉0．05），电位法对红柿椒中Vc浓度测定的回收率为98．34％～103．98％，HPLC法对Vc浓度测定的回收率为99．66％～101．49％；电位法测定红柿椒中Vc的相对标准偏差（RSD）为1.77％～2．88％，HPLC法测定Vc的RSD为0．15％～0．32％，且HPLC法线性关系良好（R^2=0．9999）。结论：2种分析法对深颜色果蔬样品中Vc浓度测定的准确度和精密度均能满足定量分析的要求，均为较理想的测试方法。

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 potentiometrie 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%0-0.32%, respectively. The HPLC data had good linear relationship （R^2=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.