Redox-iodometry: a new potentiometric method

Abstract

A new iodometric method for quantifying aqueous solutions of iodide-oxidizing and iodine-reducing substances, as well as plain iodine/iodide solutions, is presented. It is based on the redox potential of said solutions after reaction with iodide (or iodine) of known initial concentration. Calibration of the system and calculations of unknown concentrations was performed on the basis of developed algorithms and simple GWBASIC-programs. The method is distinguished by a short analysis time (2-3 min) and a simple instrumentation consisting of pH/mV meter, platinum and reference electrodes. In general the feasible concentration range encompasses 0.1 to 10(-6) mol/L, although it goes down to 10(-8) mol/L (0.001 mg Cl2/L) for oxidants like active chlorine compounds. The calculated imprecision and inaccuracy of the method were found to be 0.4-0.9% and 0.3-0.8%, respectively, resulting in a total error of 0.5-1.2%. Based on the experiments, average imprecisions of 1.0-1.5% at c(Ox)>10(-5) M, 1.5-3% at 10(-5) to 10(-7) M, and 4-7% at <10(-7) M were found. Redox-iodometry is a simple, precise, and time-saving substitute for the more laborious and expensive iodometric titration method, which, like other well-established colorimetric procedures, is clearly outbalanced at low concentrations; this underlines the practical importance of redox-iodometry.

N-Chlorotaurine, a Long-Lived Oxidant Produced by Human Leukocytes, Inactivates Shiga Toxin of Enterohemorrhagic Escherichia coli

“…This effect has to be taken into account for correct interpretation of the results, if the application of such media can’t be avoided. Therefore, we measured the decrease of oxidation capacity with redox-iodiometry [39]. To gain similar conditions as in the Vero cell assays, 3600 µl of EHEC Direct Medium were mixed with 400 µl of buffered NCT, NVC-422, or NVC-612 solutions to get final concentrations of 55 mM, 5.5 mM, 2.75 mM and 1.375 mM.…”

“…To gain similar conditions as in the Vero cell assays, 3600 µl of EHEC Direct Medium were mixed with 400 µl of buffered NCT, NVC-422, or NVC-612 solutions to get final concentrations of 55 mM, 5.5 mM, 2.75 mM and 1.375 mM. Subsequently, the redox potential after reaction with iodide was determined using a PHM250 Ion Analyzer (Radiometer, Copenhagen, Denmark), and the remaining oxidation capacity was calculated as described previously [39].…”

Active halogen compounds and proteinaceous material: loss of activity of topical anti-infectives by halogen consumption

“…For estimating the consumption effects, the reaction mixture was transformed into an equivalent iodine solution by addition of iodide, and the remaining oxidation capacity was assessed potentiometrically . To visualize the effects, c(Ox) vs time graphs were plotted, which turned out best to demonstrate the differences.…”

“…Both vessels were thermostated, stirred and connected with a salt bridge. The calculation of c(Ox) from the measured potential difference was performed as described . The t 0 value was obtained from a 1 : 1 dilution of the 0.01 m agent solution with water.…”

Nanoparticle-directed and ionically forced polyphosphate coacervation: a versatile and reversible core–shell system for drug delivery

“…The particles were again dissolved in HCl (0.1 M; pH 3). The samples were centrifuged at 3000 × g (10 min) and the ascorbic acid concentrations was determined in the supernatant applying the iodine titration/potentiometric titration technique; the cumulative profiles are given 36 . Even though ascorbic acid is considered to be most stabile at pH 3, a second method was applied for the determination of the ascorbic acid concentration which is based on the reduction of 2,6-dichloroindophenol sodium salt hydrate (# D1878, Sigma) by ascorbic acid 37 .…”