Question

Why is it necessary to standardize a indophenol solution?

Why is it necessary to titrate blank samples?

Why might the Vitamin C content be underestimated in the case of a heat processed juice sample?

Answer 1

Standardization is doing a titration to work out the exact concentration of the solution you want to use to determine the concentration of an unknown solution.

A problem with indolphenol is that it can be easily reduced, and the purity of the compound cannot be readily reproduced or estimation. It is important to estimate the concentration of an indolphenol by titration with known concentration of a vitamin C solution. This procedure is called standardization.

Once the indophenol concentration is established or standardized, this can be used to determine the concentration of Vitamin C in unknown solutions. Chemically, vitamin C is a reducing agent and a weak acid, The reaction between vitamin C and indolphenol bleaches indolphenol, and the color of the reaction mixture can be used to detect the end point of the titration and the concentration of Vitamin C can be established.

Vitamin C content might be underestimated in heat processed samples because it decays upon heating in solution state. Over a period of time the the concentration decreases leading to underestimation.

A blank titration is carried out to nullify the error that may arise during analysing the samples. This is generally performed by titrating a fixed and known concentration of titrant into a solvent with zero analyte.This allows the amount of reactive substance within the plain solvent to be determined and the correction factor can be applied during calculations as required