AB 1-100

Ascorbic acid as well as its salts and esters can be determined by titration with 2,6-dichlorophenolindophenol (DPIP) or by polarography, with the ascorbic acid being oxidized to dehydroascorbic acid:

C₆H₈O₆ - 2 H⁺ – 2 e > C₆H₆O₆

Ascorbic acid -> Dehydroascorbic acid

If 2,6-dichlorophenolindophenol is used as the titrant it is reduced by ascorbic acid:

C₁₂H₇Cl₂NO₂ + 2 H⁺ + 2 e -> C₁₂H₉Cl₂NO₂

In the titrimetric determination a bi-voltametric or photometric endpoint indication can be used. However, please remember that only the bi-voltametric indication is independent of the self-coloration of the sample.

Polarography is the most selective of the methods descibed here, as other reducing or oxidizing substances are not determined.

 AB_098_3_d.pdf (172 KB)

 AB_098_3_e.pdf (168 KB)

 AB_098_3_f.pdf (207 KB)