果汁中维C含量测定、果汁酸度

For the determination of vitamin C, there are two main methods; iodine titration method and indophenol method. In this application note, vitamin C is quantified by titrating with indophenol titrant after acidifying the sample with a mixture of metaphosphoric acid and acetic acid solution. The end point will be determined in the presence of an excess of indophenol, at the moment where the color of the solution changes from blue to red. This color change is detected photometrically in this measurement. Citric acid contained in fruit juice is quantified by acid/base titration with sodium hydroxide. The chemical reaction occurring in this titration is shown by the following formula.