POTENTIOMETRIC DETERMINATION OF SACCHARIN IN DIETARY PRODUCTS USING ACOATED-CARBON ROD ION-SELECTIVE ELECTRODE

The construction and analytical evaluation of coated-graphite sacchari n ion-selective electrodes, based on the ion pair formed between sacch arinate anion and basic dye cations incorporated in a poly(vinylchlori de)(PVC) matrix, are described. Several basic dyes such as brilliant g reen, crystal violet, malachite green, methylene blue, Nile blue, rhod amine B, toluidine blue O, Victoria blue B and violet gentian were use d in the preparation of the coated electrodes as anion-exchanger. Of t hose, only electrodes constructed with toluidine blue O, methylene blu e, viola gentian and rhodamine B presented good responses. The influen ces of membrane composition, pH and foreign food additives were invest igated. The best electrode found was 5:30:65%m/m (toluidine blue O cat ion)(saccharinate anion)/dibutylphthalate/PVC, respectively. This elec trode shows a Nernstian response over the saccharin concentration rang e from 8.1x10(-5) to 1.4x10(-2) mol L-1, a detection limit of 6.3 10(- 5) mol L-1, good selectivity, precision and a useful lifetime of at le ast nine months (over one thousand determinations for each polymeric m embrane) with a decrease of 5% of their initial potentiometric respons e (slope) at pH 2.5 (McIlvaine buffer). Sucrose, glucose, fructose, as partame, cyclamate, sorbitol, lactose, benzoic acid, citric acid, fuma ric acid ascorbic acid phosphate, nitrate and chloride do not interfer e even in significant amounts. Application of this electrode for the d etermination of saccharin in several dietary products is reported.