All-Solid-State Iodide Selective Electrode for Iodimetry of Iodized Salts and Vitamin C

Tiruwork Mequanint¹ , Ghirma Moges² *, Merid Tessma³ and Solomon Mehretu³

¹ChemTest Consulting, P. O. Box 275 Code 1250, Addis Ababa. ²Department of Chemistry, Jimma University, Jimma. ³Department of Chemistry, Addis Ababa University, P. O Box 1176, Addis Ababa, Ethiopia.

ABSTRACT:

A laboratory-made all-solid state iodide selective electrode, with Ag2 S-AgI coated on a graphite rod recovered from dry cell battery, was prepared according to previous procedures. The electrode’s linear response to iodide was in the concentration range of 10-6 M to 10-1 M with a slope of 56.85 mV/decade and a detection limit of 6×10-7 M. Iodate recovery test for laboratory formulated iodate-iodized salt was found to be 98.6 % with a standard deviation of 1.14%. The titratability of the iodized salt solution was at least 10-200 ppm potassium iodate (6-120 ppm iodine), exhibiting distinct endpoints in the range wider than the ones set in regulatory standards and reflecting that QC monitoring in production and stability decline of iodine content upon storage can be performed with the electrode method. On the basis this potentiometric titration, the application of the laboratorymade iodide electrode (vs. a saturated calomel reference electrode) was extended to the determination of iodine in commercial iodized salts. In all the iodine assays, the iodate-iodized salt was initially treated with acid and an excess of iodide before titration against Na2 S2 O3 solution. The iodine content in table salts iodized with iodide was determined by direct potentiometry. The electrode was further used for vitamin C (ascorbic acid) determinations in pharmaceutical tablets and orange juice by back titrating excess I3 - against standard Na2 S2 O3 in acidic media. The overall outcome is that the iodide ISE can be used as sharp endpoint indicator for these titrimetric reactions in place of the well known official, but visually monitored, starch- triodide end-point reaction detection.

KEYWORDS:

Solid state iodide selective; Electrode; Graphite; Vitamin C

Download this article as: 

Copy the following to cite this article: Mequanint T, Moges G, Tessma M, Mehretu S. All-Solid-State Iodide Selective Electrode for Iodimetry of Iodized Salts and Vitamin C. Orient J Chem 2012;28(4).

Copy the following to cite this URL: Mequanint T, Moges G, Tessma M, Mehretu S. All-Solid-State Iodide Selective Electrode for Iodimetry of Iodized Salts and Vitamin C. Available from: http://www.orientjchem.org/?p=11893