Determination of ascorbic acid in multivitamin tablets by thermometric titrimetry with cerium(IV)

Abstract

Cerium(IV) sulphate in aqueous sulphuric acid has been used as a titrant for the thermometric determination of ascorbic acid. The method has been applied to the analysis of vitamin tablets containing between 10 and 30 mg of ascorbic acid per tablet, and has been shown to be free from interference from tablet excipients.

Comparative analyses of two types of multivitamin tablet have been carried out using this method, two HPLC methods and visual titrimetry [cerium(IV) ammonium sulphate]. The precisions of the thermometric method and the HPLC methods are similar and acceptable. The presence of vanillin has been identified as a cause of positive bias in the visual method.

The thermometric method is inexpensive to set up and operate, relatively rapid and comparable in performance to other thermal methods for the determination of ascorbic acid.