Determination of saccharin by desorption of ferroin from silica gel

Abstract

Ferroin is strongly adsorbed on silica gel but its ion-association complexes are easily desorbed. A simple, rapid and accurate procedure for the determination of saccharin has been devised utilising these properties. The procedure is based on the quantitative formation of the ion-association complex [(Fe phen₃)²⁺(saccharin)₂^–] when saccharin dissolved in water, 60% aqueous ethanol, 70% aqueous acetone or 80% aqueous methanol is shaken with ferroin-impregnated silica gel. The absorbance of the characteristic orange colour of the ferroin ion-association complex is measured at 510 nm.

There are no interferences from glucose, sucrose and dulcin even when these constituents are present at 1 600 times the concentration of saccharin. Sodium cyclamate, sorbic acid, benzoic acid, citric acid and sodium chloride give positive errors. Although the presence of sodium hydrogen carbonate results in a low recovery of saccharin, this compound may be eliminated easily by the addition of dilute sulphuric acid.

A procedure for the routine determination of saccharin in saccharin tablets is proposed.