Iodide Electrode Research Articles

Flow-injection approach for the determination of the dynamic response characteristics of ion-selective electrodes. Part 2. Application to tubular solid-state iodide electrode

The flow-injection approach proposed in Part 1 for investigating the dynamic behaviour of flow-through detectors was applied to the study of a tubular iodide electrode prepared from a pressed precipitate of silver iodide. It was found that the electrode response cannot be described by either of the models developed in Part 1 on the basis of the concepts in the literature for the transient response mechanism of ion-selective electrodes. Scratches and microcavities in the electrode bore were observed under the microscope, most probably resulting from bore drilling. These surface non-idealities make the accessibility of the electrode surface to the analyte variable. A mathematical model developed on the basis of the assumption that part of the electrode surface is directly exposed to the flow while the remainder of the surface incorporates all microcavities in which ideal mixing exists, describes fairly successfully the experimentally obtained potential—time transients. Moreover, this study shows that the rate of response of solid-state ion-selective electrodes is in principle comparable to that of other electrochemical sensors.

Standard potentials of silver-silver iodide electrode in water + propylene glycol mixtures by electromotive force measurements and related thermodynamic quantities

Standard potentials of silver-silver iodide electrode in water + propylene glycol mixtures by electromotive force measurements and related thermodynamic quantities

Thermodynamics of silver—silver halide electrodes and thermodynamic solubility products of silver halides in glycerol + water mixtures at different temperatures

The standard potentials of silver—silver bromide and silver—silver iodide electrodes in glycerol+water mixtures containing 5, 10, 20 and 30 wt% glycerol were determined from electromotive force measurements of the cell Ag(s), AgX(s), KX(c)//KCl(c), AgCl(s), Ag(s), where X is Br or I, at seven different temperatures in the range 5–35°C. The standard potentials in each solvent are represented as a function of temperature. The standard thermodynamic functions for the electrode reactions, the primary medium effects of various solvents upon X −, and the standard thermodynamic quantities for the transfer of 1 g-ion of X − from water to the respective glycerol + water media are evaluated and discussed in the light of ion—solvent interactions as well as the structural changes of the solvents. From the values of the Ag/Ag + and Ag/AgX, X − electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide and silver iodide have been determined in glycerol + water solvent mixtures at different temperatures.

Standard potentials of the silver-silver iodide electrode and the thermodynamic properties of hydriodic acid in propylene glycol + water solvents

The electromotive force of the buffered cell: Pt, H 2 (gas, 1 atm): HOAc ( m 1), KOAc ( m 2), KI ( m 3), solvent: AgI, Ag, in propylene glycol (PG) and in 19 PG + water solvent mixtures has been measured at 5°C intervals from 0 to 55°C. The values of the standard potentials of the silver-silver iodide electrode have been determined in these solvents at the indicated temperatures. The standard potential in each solvent has been expressed as a function of temperature. The standard thermodynamic functions for the cell reaction and the standard thermodynamic quantities for the transfer of 1 mole of HI from water to the respective solvents have been evaluated. The results are interpreted in terms of the acid-base properties of the solvents as well as the preferential solvation of ions.

Chlorophyll Sensitized Solar Photovoltaic Cell with Cuprous Iodide Electrode

Chlorophyll Sensitized Solar Photovoltaic Cell with Cuprous Iodide Electrode

Determination of Iodide in Milk Using the Iodide Specific Ion Electrode and its Application to Market Milk Samples

The iodide specific ion electrode was used to measure the iodide content of raw and commercially processed whole and skim milks. Average iodide values for raw milk and commercially processed milks were 220 and 620 μ g/L, respectively. The specific ion electrode can also be used to measure iodide in milk contaminated with iodophor sanitizing agent since the milk converts iodophor titratable iodine to the ionic iodide. Since free sulhydryl groups are also detected by the iodide electrode, the effects of heating milk on free sulfhydryl formation and electrode activity were established. These data indicate that in conventionally pasteurized milk, sulfhydryl groups are non-reactive and are not detected by the iodide electrode. However, the increase in free sulfhydryl formation was reflected by an increase in iodide electrode activity at temperatures above those of pasteurization. Whereas the iodide specific ion electrode has been previously used successfully to measure iodide content of raw milk, this method has now been shown to be applicable to pasteurized milk if the conventional pasteurization time-temperature relationship of accepted public health standards is not exceeded.

Use of an Iodide-Specific Electrode to Study Lactoperoxidase-Catalyzed Iodination of l-Tyrosine

An in vitro method employing an iodide-specific electrode for monitoring lactoperoxidase-catalyzed iodination is described. The method utilized lactoperoxidase, potassium iodide, and a glucose-glucose oxidase system for the generation of hydrogen peroxide and l-tyrosine. As iodination of l-tyrosine proceeded, the free iodide concentration in solution decreased and was monitored by an iodide-specific electrode. The iodide electrode was reliable when compared to a 131I-method for measuring free iodide changes in solution. Increasing concentrations of resorcinol, a well-known inhibitor of thyroid peroxidase-catalyzed iodination, in the reaction mixture resulted in graded inhibition of the initial rate of lactoperoxidase-catalyzed l-tyrosine iodination. This in vitro system can be used to assess inhibitory activity of various anti-thyroid substances.

Standard potentials of the silver-silver iodide electrode in diethylene glycol-water mixtures at different temperatures and the related thermodynamic quantities

Standard potentials of the silver-silver iodide electrode in diethylene glycol-water mixtures at different temperatures and the related thermodynamic quantities

Continuous‐flow monitoring of lactose concentration

AbstractA specific continuous‐flow analytical system for determination of lactose concentration in a liquid mixture of constituent sugars was developed and tested based on a series of enzymatic reactions. Lactose and glucose oxidase immobilized on a phenol–formaldehyde resin were employed. More detailed study was carried out based on a reaction by‐product quantitatively detected by an available iodide electrode. A multichannel proportioning pump fed two independently operated analytical streams eliminating thus the background glucose interference. With a goal of lactose concentration control in a fermentation process, the system response time delay was shortened to approximately 15 min. Apart from optimization of the analytical system operating parameters, the study indicates also the major application problem areas: lactase inhibition by galactose, galactose oxidation by glucose oxidase, and a partial loss of glucose oxidase activity in a prolonged continuous‐flow operation. A manual Colorimetric Procedure was employed to verify the results of the potentiometric method.

Thermodynamic studies of hydrogen iodide in dioxane-water mixtures from electromotive force measurements

The standard potentials of the silver-silver iodide electrode were measured in 10,20,30 and 40% (w/w) dioxane-water mixtures at 15,25,35 and 45°C. These values have been used to determine the thermodynamic quantities Δ G t°, Δ S t°, Δ H t° for the transfer of H +I − from water to various dioxane-water mixtures. The ionic Δ G t° values for H +, Cl −, Br − and I − are determined using Feakins method. The chemical and electrical contributions of Δ G t° are also calculated using the method proposed by Roy and co-workers. The significance of these thermodynamic functions is discussed in relation to the acid—base character of the solvents.

ChemInform Abstract: STANDARD POTENTIALS OF THE SILVER‐SILVER IODIDE ELECTRODE IN AQUEOUS MIXTURES OF ETHANOL AND PROPAN‐2‐OL AT DIFFERENT TEMPERATURES. FREE ENERGIES AND ENTROPIES OF TRANSFER OF HYDROIODIC ACID AT 25°

Standard potentials of Eθ of the silver-silver iodide electrode in ethanol + water and propan-2-ol + water mixtures have been determined from the emf of the cell Pt, H2 (g, 1 atm)|HI(itm), solvent| Agl-Ag at seven temperatures ranging from 10 to 40° for ethanol and from 5 to 35° for propan-2-ol. Free energies ΔSgqitt of transfer HI obtained therefrom have been briefly discussed in the light of ion-solvent interactions and solvent structure.

Standard potentials of the silver-silver iodide electrode in aqueous mixtures of ethanol and propan-2-ol at different temperatures. Free energies and entropies of transfer of hydroiodic acid at 25°

Standard potentials of E θ of the silver-silver iodide electrode in ethanol + water and propan-2-ol + water mixtures have been determined from the emf of the cell Pt, H 2 (g, 1 atm)|HI(itm), solvent| Agl-Ag at seven temperatures ranging from 10 to 40° for ethanol and from 5 to 35° for propan-2-ol. Free energies ΔS gq itt of transfer HI obtained therefrom have been briefly discussed in the light of ion-solvent interactions and solvent structure.

Ion-selective electrodes in organic functional group analysis: Micro- and submicro-determination of thiocarbonyl and thiol groups using the silver/sulphide and iodide electrodes

Thiocarbonyl and thiol groups in organic compounds are determined by reaction with 1N iodine in carbon tetrachloride in the presence of pyridine, whereby 4 equivalents and 1 equivalent of iodide ion are quantitatively released per group, respectively. The iodide ions in an aqueous extract are potentiometrically titrated with silver nitrate using the solid-state silver/sulphide selective electrode. The results obtained with samples down to 70μg show an average recovery of 98.6% and no interferences are caused by unsaturated functions. Measurement of the iodide ion using the iodide ion-selective electrode and the known addition technique gives results with an absolute error of 2%.

Silver/silver iodide electrodes of the second kind as sensors for cyanide

Silver/silver iodide electrodes of the second kind prepared by electrolytic coating of silver electrodes are advantageous as sensors for cyanide. They are inexpensive and exhibit characteristics similar to those of commercially available ion-selective electrodes. They can be regenerated easily when necessary; this eliminates the lifetime problems generally inherent in iodide electrodes used as cyanide sensors. The preparation, properties and selectivity characteristics of the second-kind iodide electrode are described.

Ion-selective electrodes in organic functional group analysisMicrodetermination of nitrates and nitramines with use of the iodide electrode

A simple, selective and accurate method has been described for the rapid micro and submicro determination of organic nitrates and nitramines. It is based on reaction with mercury-sulphuric acid mixture for 5 min at room temperature followed by potentiometric titration of the mercurous ions released, a solid-state iodide-sensitive electrode being used. Three equivalents of potassium iodide as titrant are consumed per mole of nitrate or nitramine group. The results obtained, with sample sizes ranging from 1.0 to 50 mumole, are precise to +/- 0.2% and the average recovery is 99%. None of the other nitrogenous functional groups responds to this reaction.

Electrokinetic flow through porous media composed of fine cylindrical capillaries

Electrokinetic flow through fine cylindrical capillaries was investigated experimentally, using dilute solutions of potassium iodide in purified water as the electrolyte. Two types of porous media were studied: a fused array of borosilicate glass capillaries each 2 μm in diameter and 1.91 μm long with a moderatly high zeta potential; and a polycarbonate filter membrane containing nearly uniform circular pores each about 0.1 μm in diameter and 12 μm long, with a relatively low zeta potential. The electrokinetic radius was varied by varying the concentration of potassium iodide in the solution, the conductivity of which was continuously monitored. Streaming potentials were measured using platinum electrodes for the glass disc and silver iodide electrodes for the polycarbonate membrane. An apparent effect of pressure drop on the ratio of streaming potential to pressure drop for the polycarbonate membrane, which could serve as an explanation for the non-Darcy flow behavior reported by others for low liquid velocities through certain porous media, was rationalized as fortuitous by invoking arguments recently presented by Ball and Fuerstenau [7]. The electroviscous retardataion effect was measured for the glass disc by comparing the product of pressure drop and displacement time for a fixed volume of liquid with the corresponding product obtained under conditions of high electrokinetic radius (small double layer thickness). The results for both streaming potential and electroviscous retardation effect are compared with the theory of Rice and Whitehead [1] for low zeta potentials, as well as with the more recent theory of Levine et al. [2] for all zeta potentials. The data support the latter theory more than the former.

Determination of total iodine in milk by X-ray fluorescence spectrometry and iodide electrode.

Determination of total iodine in milk by X-ray fluorescence spectrometry and iodide electrode.

Free energies and entropies of transfer of hydrobromic and hydroiodic acids from water to t-butyl alcohol + water mixtures from electromotive force measurements at different temperatures (5—35°C)

Free energies, ΔG0t and entropies, ΔS0t of transfer of hydrobromic and hydroiodic acids from water to t-butyl alcohol + water mixtures containing 10, 20, 30 and 50 % t-butyl alchol by weight have been evaluated using the corresponding values of the standard potentials, E0, of silver–silver bromide and silver–silver iodide electrodes in these solvents obtained from electromotive force measurements at seven different temperatures ranging from 5 to 35°C performed on the cell Pt, H2(g, 1 atm)|HX(m), solvent|Ag-AgX, where X = Br or I. These and the corresponding values for HCl obtained from E0 data given in literature were used to evaluate ΔG0t for individual ions by the “extrapolation procedure”. In contrast with other aqueous organic solvents, humps or kinks in the ΔG0t against composition profiles occur at water-rich compositions reflecting the strong structural characteristics of this solvent system in that region. The variation of entropies of transfer with composition has been interpreted in terms of marked structure-promotion of water and consequent ion-dehydration at small concentrations of t-butyl alcohol and of the formation of alcohol–water complexes at somewhat higher contents of t-butyl alcohol. The irregular order Br– > I– > Cl– in water-rich regions for the entropy profiles is suggested to be due to the formation of charge-transfer complexes of the iodide ion with t-butyl alcohol.

Behaviour of the silver-silver bromide and the silver-silver iodide electrodes in formamide at different temperatures

From the e.m.f. measurements of the buffered cells of the type ��������������������� Pt, H2|HOAc(m1), KOAc(m2), KX(m3)|AgX-Ag the standard potentials of the Ag-AgX electrodes have been determined, in formamide, at nine different temperatures in the range 5-45�. The standard potentials of the Ag-AgX electrodes obtained at 25� are in good agreement with those obtained from the study of the cells ������������������ Ag-AgX|KX(m3), KOAc(m2), HOAc(m1), QH2-Q|Pt at 25�, where X is Br or I. The cell �������������������������Pt,H2|HBr(m)|AgBr-Ag has been further studied in this solvent at 25� with a view to having an independent check on these buffered cells for the standard potential of the Ag-AgBr electrode. The standard thermodynamic quantities (ΔG�, ΔH�, and ΔS�) for the corresponding cell reactions have been calculated from the e.m.f. data over the range, 5-45�.

Evaluation of an Ion Selective Electrode Monitor for Total Oxidants

The iodide ion selective electrode has potential use for continuous monitoring of total oxidants in ambient air. Total oxidants are measured coulometrically or colorimetrically after oxidation of neutral buffered Kl solution (0.6-1.2M) to free iodine. On the other hand, the iodide electrode can measure much more dilute solutions (<10-4M). The iodide electrode measures the disappearance of iodide from the absorbing solution. The detector is made from an iodide electrode, reference electrode, an expanded scale pH meter, and millivolt recorder. The iodide electrode shows a constant Nernstian —59 mv change per decade over a dilute solution range although the absolute voltage shows a drift of 1 mv/day. A continuous iodide electrode air monitor was set up and investigated for ambient monitoring. Operational parameters as air and solution flow rates and electrode parameters as response time at different iodide concentrations were investigated. Statistical comparison was made with a Beekman colorimetric total oxi...