Iodide Ion-selective Electrode Research Articles

Iodine speciation in coastal and inland bathing waters and seaweeds extracts using a sequential injection standard addition flow-batch method

The present work describes the development of a sequential injection standard addition method for iodine speciation in bathing waters and seaweeds extracts without prior sample treatment. Iodine speciation was obtained by assessing the iodide and iodate content, the two inorganic forms of iodine in waters. For the determination of iodide, an iodide ion selective electrode (ISE) was used. The indirect determination of iodate was based on the spectrophotometric determination of nitrite (Griess reaction). For the iodate measurement, a mixing chamber was employed (flow batch approach) to explore the inherent efficient mixing, essential for the indirect determination of iodate. The application of the standard addition method enabled detection limits of 0.14µM for iodide and 0.02µM for iodate, together with the direct introduction of the target water samples, coastal and inland bathing waters. The results obtained were in agreement with those obtained by ICP-MS and a colorimetric reference procedure. Recovery tests also confirmed the accuracy of the developed method which was effectively applied to bathing waters and seaweed extracts.

A Selective Iodide Ion Sensor Electrode Based on Functionalized ZnO Nanotubes

In this research work, ZnO nanotubes were fabricated on a gold coated glass substrate through chemical etching by the aqueous chemical growth method. For the first time a nanostructure-based iodide ion selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion exchanger and the electromotive force (EMF) was measured by the potentiometric method. The iodide ion sensor exhibited a linear response over a wide range of concentrations (1 × 10−6 to 1 × 10−1 M) and excellent sensitivity of −62 ± 1 mV/decade. The detection limit of the proposed sensor was found to be 5 × 10−7 M. The effects of pH, temperature, additive, plasticizer and stabilizer on the potential response of iodide ion selective electrode were also studied. The proposed iodide ion sensor demonstrated a fast response time of less than 5 s and high selectivity against common organic and the inorganic anions. All the obtained results revealed that the iodide ion sensor based on functionalized ZnO nanotubes may be used for the detection of iodide ion in environmental water samples, pharmaceutical products and other real samples.

Bifunctional Ion‐Selective Electrode Based on C60‐Cryptand 22 for Silver and Iodine Ions

AbstractFullerence C60‐cryptand 22 was prepared and successfully applied as the electric carrier in the PVC electrode membrane of a bifunctional ion‐selective electrode for cations, e.g., Ag+ ions as well as anions, e.g., I− ions. The bifunctional ion‐selective electrode based on C60‐cryptand 22 can be applied as a Silver (Ag+) ion selective electrode with an internal electrode solution of 10−3 M AgNO3 in water (pH = 6.3), or as an Iodide (I−) ion selective electrode with an acidic internal electrode solution of 10−4 M KI(aq) (pH = 2) in which the cryptand 22 is protonated, and the C60‐cryptand 22 is changed to C60‐Cryptand22–H+ and becomes an anionic electro‐carrier to absorb the I− ion. The Ag+ ion selective electrode based on C60‐cryptand 22 gave a linear response with a near‐Nernstian slope (59.5 mV decade−1) within the concentration range 10−1‐10−3 M Ag+(aq). The Ag+ ion electrode exhibited comparatively good selectivity for silver ions, over other transition‐metal ions, alkali and alkaline earth metal ions. The Ag+ ion selective electrode with good stability and reproducibility was successfully used for the titration of Ag+(aq) with Cl− ions. The Iodide (I−) Ion selective electrode based on protonated C60–cryptand22‐H+ also showed a linear response with a nearly Nernstian slope (58.5 mV decade−1) within 10−1 ‐ 10−3 M I− (aq) and exhibited good selectivity for I− ions and had small selectivity coefficients (10−2–10−3) for most of other anions, e.g., F− , OH−, CH3COO−, SO42−, CO32−, CrO42−, Cr2O72− and PO43− ions.

Bis(trans‐cinnamaldehyde)‐1,3‐propanediimine) mercury(II)chloride, [Hg(BPPPB)Cl2] as Carrier for Construction of Iodide Selective Electrode

Highly selective poly(vinyl chloride) (PVC) membrane of iodide ion selective electrode based on the application of bis(trans‐cinnamaldehyde)‐1,3‐propanediimine)mercury(II)chloride [Hg(BPPPB)Cl2] as new carrier by coating the membrane ingredient on the surface of graphite electrodes has been reported. The effect of various parameters including membrane composition, pH and possible interfering anions on the response properties of the electrode were examined. At optimum conditions, the proposed sensor exhibited Nernstian responses toward iodide ion in a wide concentration range of 1×10-6 to 0.1 M with slopes of 58.0±0.8 mV per decade of iodide concentration over a wide pH range of 3‐11 with detection limit of detection of ~8×10-7 M. The sensors have stable responses times of ≤ 5 s and give stable response after conditioning in 0.05 M KI for 24 h with its response is stable at least 2 months without any considerable divergence in its potential response characteristics. The electrodes were successfully applied for the direct determination of iodide ion in water sample and as indicator electrodes in precipitation titrations.

Evaluation of iodine, iron, and selenium in biological samples of thyroid mother and their newly born babies

Background There is accumulating facts that the metabolism of essential trace elements is altered in thyroid patients. Aim The aim of present study was to compare the status of essential trace elements, iodine, iron (Fe), and selenium (Se) in biological samples (serum and urine) of goitrous mothers (age ranged 30–40) and their newly born infants ( n = 76). An age matched 68 non-goitrous mothers and their infants, residing in the same locality, were selected as referents. For a comparative study, the biological samples of non-goitrous and goitrous pregnant and non pregnant female subjects of the same age group and socio-economic status were also analyzed. Methods The Fe and Se concentrations in biological samples were determined by a flame and hydride generation atomic absorption spectrometry respectively, while iodine was measured by iodide-ion selective electrode, prior to microwave assisted acid digestion. The validity and accuracy of the methodology was checked by certified reference materials. Results The mean values of iodine, Fe and Se in serum and urine samples of thyroid mothers and their infants were significantly lower as compared to the referent mothers-infants pairs ( p < 0.01). Conclusions The deficiencies of essential trace elements may adversely affect the health of women and their neonates.

Characterization of home-made silver sulphide based iodide selective electrode

Polycrystalline silver sulphide/silver iodide ion selective electrodes (ISEs) with four different compositions, 9:1, 2:1, 1:1, 1:9 Ag 2S–AgI mole ratios, have been fabricated in the laboratory and characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). X-ray diffraction studies show the presence of Ag 3SI, Ag 2S and AgI crystalline phases in the electrode material. The electrode surfaces have been found to become smoother and lustrous with increasing percentage of silver sulphide in silver iodide. ISE 1:1, ISE 2:1 and ISE 9:1 all responded in Nernstian manner with slopes of about 60 mV/decade change in iodide ion concentration in the linear range of 1 × 10 −1 to 1 × 10 −6 M while ISE 1:9 showed sub-Nernstian behavior with slope of about 45 mV up to the concentration 1 × 10 −5 M. Two capacitive loops, one corresponding to the charge transfer process at metal electrode and the back contact and a second loop corresponding to the charge transfer process at membrane–electrolyte interface have been observed at high and low frequency ranges, respectively. Mott–Schottky analysis shows that the materials are n-type semiconductors with donor defect concentrations in the range of 5.1 × 10 14 to 2.4 × 10 19/cm 3.

Construction of New Iodide Ion-Selective Electrodes Based on New Ionophores: Comparison of the Effect of Structures and Additives on Electrode Response

New iodide ion-selective electrodes based on bis(2-methyl-3-phenyl-propenylidene)1,2-propanediamine)mercury(II) bromide [Hg(BMPPMB)Br2], bis (5-bromo salicylaldehyde) ethylenediimine vanadyl(IV) [VO(5-Br Salen)], and bis(5-bromo salicylaldehyde) ethylenediimine uranyl(VI) [UO2(5-Br Salen)] carriers are described. The electrodes exhibited Nernstian slopes of -58.3 +/- 1.0, -58.5 +/- 1.4, and -59.0 +/- 1.2 mV/decade for Hg(BMPPMB)Br2, VO(5-Br Salen), and UO2(5-Br Salen) iodide ion concentration in the range of 1.0 x 10(-6)-0.1 M, with detection limits of about 0.6, 0.5, and 0.3 microM, respectively. The potentiometric responses of the electrodes were independent of pH over the range 1.7-10.6, 2.2-11.3, and 2.1-11.1, with satisfactory reproducibility. The electrodes had response times of < or =5 s and could be used for at least 84, 80, and 100 days for Hg(BMPPMB)Br2, VO(5-Br Salen), and UO2(5-Br Salen), respectively, without any considerable divergence in their potential responses.

Preparation and application of a new glucose sensor based on iodide ion selective electrode

An electrode for glucose has been prepared by using an iodide selective electrode with the glucose oxidase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 10 min at room temperature. The H 2O 2 formed from the reaction of glucose was determined from the decrease of iodide concentration that was present in the reaction cell. The iodide concentration was followed from the change of potential of iodide selective electrode. The potential change was linear in the 4×10 −4 to 4×10 −3 M glucose concentration (75–650 mg glucose/100ml blood) range. The slope of the linear portion was about 79 mV per decade change in glucose concentration. Glucose contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, uric acid, iron(III) and Cu(II) was observed. Since the iodide electrode used was not an AgI–Ag 2S electrode, there was no interference of common ions such as chloride present in biological fluids. The slope of the electrode did not change for about 65 days when used 3 times a day.

Simple flow injection system for colorimetric determination of iodate in iodized salt

This work presents a flow injection (FI) system that was developed for determination of iodate. The system utilizes the oxidation of iodide by the analyte to iodine, which subsequently forms tri-iodide. In the presence of starch, the blue I 3 −–starch complex is developed within the sample zone and can be colorimetrically detected at 590 nm. Optimization was carried out to make the system suitable for quantitating iodate added to table salts. To prevent accumulation of the blue complex residue on walls of tubing and the flow cell, a port was placed in the system for injection of 10 −3 M thiosulfate plug (100 μl). An injection of this cleaning solution after each sample injection is recommended to avoid positive baseline shift. By means of the paired t-test, the amounts of iodine (mg I kg −1) were statistically compared with the results determined by titration and by iodide ion selective electrode. No significant disagreement at 95% confidence was observed. The proposed system is very simple, uses common chemicals and provides rapid analysis (65 injections per h) with high precision (R.S.D.=0.66%, n=10). A detection limit of 2 mg I kg −1 salt can be achieved.

Flow injection determination of iodide ion in a photographic developing solution using iodide ion-selective electrode detector

A potentiometric flow injection determination method for iodide ion in a photographic developing solution was proposed by utilizing a flow-through type iodide ion-selective electrode detector. The sensing membrane of the electrode was Ag 2S–AgI membrane. The response of the electrode detector as a peak-shape signal was obtained for injected iodide ion in a photographic developing solution. A linear relationship in the subnernstian zone was found to exist between peak height and the concentration of the iodide ion in a photographic developing solution in a concentration range from 0 to 6.0×10 −5 mol l −1. The relative standard deviation for ten injections of 2×10 −5 mol l −1 iodide ion in a photographic developing solution was 0.96% and the sampling rate was approximately 12–13 samples h −1. The iodide ion could be determined under coexisting of an organic reducing reagent and inorganic electrolytes of high concentration in a photographic developing solution sample solution by the present method.

Iodinated P(MMA‐NVP): an efficient matrix for disinfection of water

Polymethyl methacrylate-N-vinyl-2-pyrrolidone P(MMA-NVP) copolymer was synthesized in an inert atmosphere by bulk polymerization using azobis-isobutyronitrile (AIBN) as initiator. The copolymer was crushed, and ground to a defined particle size and iodinated. The iodinated copolymer matrix was washed thoroughly in a suitable solvent so as to remove any residual iodine and characterized using solubility, swelling, viscosity, FT-IR, and 1H-NMR studies. The iodinated copolymer was then packed in a refill cartridge specially designed for the purpose. The release of iodide ions from the iodinated matrix was measured in a continuous flow system by directly attaching the cartridge to the water tap and adjusting the flow rate. The water samples were collected at regular intervals and estimated for the concentration of iodide ions using an iodide ion selective electrode. The antimicrobial activity of the copolymer was estimated against bacterial (both Gram-positive and -negative) and fungal species using the zone of inhibition technique. In addition, efficacy of the iodinated copolymer against a variety of microbes was established by inoculating a microbial culture in the water reservoir and measuring the rate of survival of microbes after passing through the copolymer-filled column. The iodinated copolymer was found to be effective against a variety of microbes and remained so completely until 5000 L of water had passed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1109–1116, 2000

Kinetics of the Dushman reaction at low I- concentrations

We have reinvestigated the kinetics of the Dushman reaction, IO3−+5 I−+6 H+→3 I2+3 H2O, under the conditions of the oscillating Bray–Liebhafsky reaction, perchloric acid solutions and low iodide concentrations, using a CSTR (continuous flow stirred tank reactor) and an iodide ion selective electrode. We show that it is possible to get meaningful results with this electrode at iodide concentrations in the range [I−]=5×10−8 to 5×10−6 M. The experimental rate law is r=[IO3−][H+]2 {k′[I−]+k″[I−]2} with k′=(1200±150) M−3 s−1 and k″=(4.2±0.8)×108 M−4 s−1 at 25°C and 0.2 M ionic strength. It is the first time that the two terms, first and second order in [I−], are observed simultaneously.

Enzymatic determination of choline in milk using a FIA system with potentiometric detection.

The development of a FIA system for the determination of total choline content in several types of milk is described. The samples were submitted to hydrochloric acid digestion before injection into the system and passed through an enzymatic reactor containing choline oxidase immobilised on glass beads. This enzymatic reaction releases hydrogen peroxide which then reacts with a solution of iodide. The decrease in the concentration of iodide ion is quantified using an iodide ion selective tubular electrode based on a homogeneous crystalline membrane. Validation of the results obtained with this system was performed by comparison with results from a method described in the literature and applied to the determination of total choline in milks. The relative deviation was always < 5%. The repeatability of the method developed was assessed by calculation of the relative standard deviation (RSD) for 12 consecutive injections of one sample. The RSD obtained was < 0.6%.

Fabrication of a multilayer film electrode containing porphyrin and its application as a potentiometric sensor of iodide ion

A novel iodide ion-selective electrode has been produced based on a molecular deposition technique in which water-soluble porphyrin was alternatively deposited with water-soluble polypyrrole on a 2-aminoethanethiol modified silver electrode. The potentiometric response is independent of pH of the solution between pH 1 and 7, while it is dependent on the nature of the medium. The electrode has a linear dynamic range between 1.6×10 −6 and 0.1 M with a Nernstian slope of 59 mV/decade and a detection limit of 1.0×10 −6 M in acetate buffer (0.1 M, pH 4.6). The electrode has the advantages of low resistance, short conditioning time and fast response.

Mercurimetric Potentiometric Determination of Barbiturates Using a Solid-State Iodide Ion-Selective Electrode

A simple potentiometric method is described for mercurimetric titration of barbiturates using a solid-state iodide ion-selective electrode. The optimum titration conditions involve the use of a borate buffer of pH 9–10 as a medium and mercury(II) perchlorate of pH 1.7–1.9 as a titrant. Under these conditions, titration curves with two sharp consecutive inflection breaks are obtained. The first inflection corresponds to quantitative and stoichiometric reaction of barbiturates with mercury(II) and the second break is due to the reaction of the buffer with the titrant. No interferences are caused by Cl−, Br−, PO4 3- and many excipients and diluents commonly used in the drug formulations. Determination of barbiturates in various pharmaceutical preparations gives reproducible results with an average recovery of 99.1% of the nominal (st.dev. 0.3 %) and the method offers significant advantages over the titrimetric method of the British Pharmacopoeia.

Ion chromatographic determination of iodide in urine and serum using a tubular ion-selective electrode based on a homogeneous crystalline membrane

The use of a laboratory-made iodide ion-selective electrode with tubular configuration and based on a crystalline membrane (AgI/Ag2S) as the detector for ion chromatographic determination of iodide in urine and serum is described. A CIS reversed-phase column was coated withN-cetylpyridinium chloride to prepare a low-exchange-capacity analytical column and with hexadecyltrimethylammonium bromide to prepare a concentrator pre-column. A 2.0 ml min−1 flow rate of deionized water and 0.1 mol 1−1 KNO3 solution was used for the pre-concentration and for the chromatographic separation, respectively. For optimum performance of the detector a background level of iodide was added into the column effluent. A linear relationship (r = 0.9997) between tubular electrode potential (as peak height) and iodide concentration in the range 5–400 μg 1−1 and a detection limit of 1.47 μg 1−1 were obtained. The method shows good reproducibility for both peak height (2.2% RSD) and retention time (1.3% RSD). Recoveries on its application to the samples were 93.0–100.9% for urine and 91.4–106.0% for serum.

Preparation of an iodide ion-selective electrode by chemical treatment of a silver wire.

The preparation and application of an iodide ion-selective electrode, prepared by chemical treatment of a silver wire with Hg(2+) is described. The electrode is suitable for the direct potentiometric measurement of iodide in aqueous solutions with concentrations down to 1 x 10(-6) mol/L. It can be used for potentiometric measurements of various compounds (vitamin C, glutathione).

Binding of iodide to bovine serum albumin and protamine studied with an ion-selective electrode

Binding of iodide ion to bovine serum albumin and protamine was studied using an iodide ion-selective electrode. Binding was found to be significant with bovine serum albumin but insignificant with protamine. The data for the iodide-bovine serum albumin system were treated according to the Klotz equation and the fit was found to be quite good. Number of iodide ions bound per bovine serum albumin molecule was calculated as one and the equilibrium constant for this binding was determined to be 5.3 × 10 3. Insignificant binding to protamine and single binding to each bovine serum albumin molecule were explained in terms of the amino acid compositions and secondary structures of these proteins.

Application of an iodide ion-selective electrode to the determination of anionic polyelectrolytes and colloids with a cationic surfactant

The analytical application of an iodide solid-state ion-selective electrode is described for the titration, in the low mg 1−1 range, of polyanions with hexadecylbenzyldimethylammonium chloride, a cationic surfactant. Reliable calibration graphs were obtained at concentrations up to 10 mg 1−1. The feasibility of the titration method for determining the charge density of natural colloids such as humic acids and clays is also shown. The effects of surfactant concentrations of up to 30 mg 1−1 on the polyanion titration show that anionic sufactants are co-titrated.

Preparation and Potentiometric Determination of Quaternary N-Methiodides of Phenothiazine Derivatives

Abstract A method for the quantitative preparation of quaternary N-methiodides of phenothiazine derivatives has been developed. The products of the quaternization reaction were determined by potentiometric titration or by direct measurement of the potential of the indicator iodide ion-selective electrode.