Application Of Graphite Based Solid State Iodide Selective Electrode For The Determination Of Iodine In Iodized Salts And Ascorbic Acid

A laboratory-made iodide selective solid-state electrode (Ag2S-AgI) was prepared. The electrode response was linear in the iodide concentration range of 10-6 M to 10-1 M, with a slope of 56.85 mV/decade and detection limit of 6x10-7 M iodide. The application of the laboratory-made iodide electrode (vs. a saturated calomel reference electrode) was investigated for direct potentiometric titration of iodized salts and for potentiometric back titration of vitamin C in pharmaceutical products and orange juices. The electrode was used as an endpoint indicator system in place of the traditional starch-triiodide complex. Vitamin C with I3- was back titrated against Na2S2O3 in acidic media while acidified samples of table salt iodized with iodate (in presence of excess concentration of iodide) was directly titrated with Na2S2O3. The curves of both titrations exhibited distinct endpoints down to 10 ppm as potassium iodate

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