Determination of iodine using a kinetic method with an iodide ion-selective electrode

Abstract

A method for the determination of iodine is described, based on the reaction of acetone, iodine and potassium hydroxide as monitored with an iodide-selective electrode. This method is more sensitive than those previously de~cribed.l-~ Kinetic methods of analysis and ion-selective electrodes have recently been recognised as useful means for the determination of individual elements, catalysts, enzymes, substrates, inhibitors and activator^.^-^ In a previous paper Altinata and Pekin described the determination of molybdenum and tungsten by using an iodide-activity electrode.10Nikitin and Kochkin4 have determined iodine by using a kinetic method, based on the determination of the rate of development of turbidity in solution with time. Three readings were taken of the turbidity time (tz) and they carried out similar measurements on two control solutions (tl and t2). They calculated the concentration of the iodine used as a substrate for the reaction between acetone, iodine and potassium hydroxide by applying the equation given in the literature.There are three steps in the reaction between acetone, iodine and potassium hydroxide. These partial reactions can be summarised as the following net reaction:

A comparative analytical assessment of iodides in healthy and pathological human thyroids based on IC-PAD method preceded by microwave digestion

“…spectrophotometric methods based on catalytic reactions [16], X-ray fluorescence spectrometry [17], spectrophotometry [18], the use of ion-selective electrodes [19,20], inductively coupled plasma mass spectrometry (ICP-MS) [21][22][23] or neutron activation analysis (NAA) [24]. Most reports concerning thyroid analysis are grounded on research into the animal tissue and, unfortunately, scientific studies on the iodine content in human thyroids are scarce.…”

Kinetic determinations and some kinetic aspects of analytical chemistry

“…The formation of iodoform from acetone and iodine in KOH solution has been proposed for the determination of iodine in aqueous solution by application of the method of tangents and potentiometric monitoring with an iodide-ion-selective electrode (118).…”

Ion-selective electrodes

“…Ca23 (5 X 10'4-5 X 10"' M) film electrode based on mono(2-ethylhexyl) phosphate in PVC 67 4. Hg23 (2.5 X 10"5-10"2 M) electrode based on ionic association compound of Brilliant Green w'ith Hgl," 5. Hg23 (>10~4 M) and TI33 (>5 X 10"6 M) electrodes based on tetradecylphosphonium HgCl," or T1C14" in PVC 6. Hg23 (10"5-10"' M) electrode based on PAN chelate of Hg23 dissolved in CHC13 7.…”