A highly selective iodide electrode based on the bis(benzoin)-semiethylenediamine complex of mercury(II) as a carrier

A new PVC membrane electrode based on the bis(benzoin)-semiethylenediamine (BBSEA) complex of Hg(II) is described which exhibits excellent selectivity towards iodide, related to the unique interaction between the central Hg(II) and the iodide ion. The electrode has a linear response to iodide from 5 × 10^–7 to 5 × 10^–4 mol/L with a slope of 58 mV/dec.(20°C). The response characteristics were investigated in detail and the mechanism of the electrode was studied with AC impedance and quartz crystal microbalance (QCM) techniques. It can be used for iodide determinations in drug preparations. Received: 29 January 1997 / Revised: 17 April 1997 / Accepted: 20 April 1997     

Vermiculite clay mineral as an effective carbon paste electrode modifier for the preconcentration and voltammetric determination of Hg(II) and Ag(I) ions

A vermiculite modified carbon paste electrode (VMCPE) was employed for the in situ preconcentration of traces of Hg(II) and Ag(I) via an ion-exchange route. Heavy metal ions were accumulated in Britton-Robinson (BR) buffer pH 7 for Hg(II) and pH 6 for Ag(I), and afterwards reduced at –0.7 V vs. Ag/AgCl in the separate measurement solution (BR buffer pH 5 + 0.05 mol/L NaNO₃) prior to the anodic stripping square-wave voltammetric (ASSWV) detection. For Hg(II) ions, at 15 min accumulation, a linear range from 1.0 × 10^–7 to 8.0 × 10^–6 mol/L was obtained, with a 5.7 × 10^–8 mol/L limit of detection. The VMCPE response was linear for Ag(I) ions in the concentration range from 2.0 × 10^–7 to 8.0 × 10^–6 mol/L, at 10 min accumulation with a corresponding limit of detection of 6.3 × 10^–8 mol/L. The relative standard deviation of the analytical procedure including accumulation from a 5 × 10^–7 mol/L solution of Hg (15 min) or Ag(I) (10 min), electrolysis, ASSWV detection, regeneration and activation of the VMCPE, was 4% (n = 6). The optimisation of the parameters for the application of the VMCPE in combination with ASSWV detection is presented and discussed.     

Preparation of an ion-selective electrode by chemical treatment of copper wire for the measurement of copper(II) and iodide by batch and flow-injection potentiometry

The preparation of an ion-selective electrode by chemical treatment of copper wire and its application for the measurements of copper (II) and iodide ions is described. The proposed reaction mechanism at the sensing surface, which explains the response of the electrode to Cu²⁺ and iodide ions, is discussed. The prepared electrode was suitable for direct potentiometric measurements of iodide and copper (II) in batch experiments down to concentrations of 1 × 10^–5 mol L^–1. A tubular electrode, prepared in the same way, may be used as a potentiometric sensor in a flow-injection analysis for Cu (II) and/or iodide determinations.     

Determination of Hg(II) ions in water samples by a novel Hg(II) sensor,based on calix[4]arene derivative

A PVC membrane electrode for Hg(II) ions, based on a new cone shaped calix[4]arene (L) as a suitable ionophore was constructed. The sensor exhibits a linear dynamic in the range of 1.0 × 10^?6–1.0 × 10^?1 M, with a Nernstian slope of 29.4 ± 0.4 mV decade^?1, and a detection limit of 4.0 × 10^?7 M. The response time is quick (less than 10 s), it can be used in the pH range of 1.5–4, and the electrode response and selectivity remained almost unchanged for about 2 months. The sensor revealed comparatively good selectivity with respect to most alkali, alkaline earth, and some transition and heavy metal ions. It was successfully employed as an indicator electrode in the potentiometric titration of Hg²⁺ ions with potassium iodide, and the direct determination of mercury content of amalgam alloy and water samples.     

Synthesis,characterization and electrochemical behavior of a new diimine-dioxime compound and its application in developing Hg(II)-selective membrane electrode

In this work, a new diimine-dioxime compound (N,N′-bis[1-biphenyl-2-hydroxyimino-2-(4-chloroanilino)-1-ethylidene]-1,4-phenylenediamine) was synthesized and characterized by a combination of elemental analyses, FT-IR, ¹H- and ¹³C-NMR spectra. The extraction ability of the new compound has been examined in chloroform by using several transition metal picrates such as Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II) and Hg(II). It has been observed that diimine-dioxime compound shows a high affinity to Hg(II) ion. The electrochemical measurements of the compound were performed by cyclic voltammetry in acetonitrile solution at room temperature, and two irreversible oxidation waves were observed. A Hg(II)-selective electrode based on the diimine-dioxime compound has been developed. The electrode showed linear responses with Nernstian slopes of 33 ± 1 mV per decade over a wide concentration range (1.0 × 10^?2–8.0 × 10^?6 M). The limit of detection was 2.4 × 10^?6 M. The electrode has a response time about 10–15 s and it did not show a considerable divergence in its potential response over a period of 1 month. The proposed electrode revealed selectivity towards Hg(II) ion in the presence of various cations. The electrode could be used over a wide pH range of 4.0–9.0. The electrode can be successfully used as an indicator electrode for potentiometric titration of Hg(II) with EDTA.     

Iodide‐Selective Electrodes Based on Bis[N(2‐methyl‐phenyl) 4‐Nitro‐thiobenzamidato]mercury(II) and Bis[N‐phenyl 3,5‐Dinitro‐thiobenzamidato]mercury(II) Carriers

Highly selective poly(vinyl chloride) (PVC) membrane electrodes based on recently synthesized mercury complexes including Hg(Nmpntb)₂ and Hg(Npdntb)₂ as new carriers for iodide‐selective electrodes by incorporating the membrane ingredients on the surface of graphite electrodes are reported. The effect of various parameters including the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrodes. Both sensors exhibited Nernstian responses toward iodide over a wide concentration range of 7×10^?7 to 0.1 M and 1×10^?6 to 0.1 M, with slopes of 59.6±0.8 and 58.9±0.9 mV per decade of iodide concentration and detection limit of 3×10^?7 M and 7×10^?7 for Hg(Npdntb)₂ and Hg(Nmpntb)₂, respectively, over a wide pH range of 3–11. The sensors have response times of ≤5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrodes show good ability to discriminate iodide over several inorganic and organic anions. The electrodes were successfully applied to direct determination of iodide in synthetic mixture, waste water and drinking water and as indicator electrodes in precipitation titrations.     

Liquid-state mercury(II) ion-selective electrode based on N-(O,O-diisopropylthiophosphoryl)thiobenzamide

A liquid ion-exchange electrode containing a complex of mercury(II) with N-(O,O-diisopropylthiophosphoryl)thiobenzamide in carbon tetrachloride is described. The electrode shows excellent sensitivity and good selectivity. The slope of the calibration graph is 29.0 mV/pHg²⁺ in the pHg²⁺ in the pHg²⁺ range 2–15.2 in mercury(II) ion buffers. The electrode can be used for determination of 5 × 10^?5–10^?2 M Hg(II) in the presence of 10^?2 M Cu(II), Ni(II), Co(II), Zn(II), Pb(II), Cd(II), Mn(II), Fe(III), Cr(III), Bi(III) or Al(III) ions and in the presence of 10^?3 M Ag(I) ions. It can bealso used for end-point detection in titrations with EDTA of 10^?3–10^?4 M mercury(II) at pH 2.     

Preparation of an ion-selective electrode by chemical treatment of copper wire for the measurement of copper(II) and iodide by batch and flow-injection potentiometry

The preparation of an ion-selective electrode by chemical treatment of copper wire and its application for the measurements of copper (II) and iodide ions is described. The proposed reaction mechanism at the sensing surface, which explains the response of the electrode to Cu²⁺ and iodide ions, is discussed. The prepared electrode was suitable for direct potentiometric measurements of iodide and copper (II) in batch experiments down to concentrations of 1 × 10^–5 mol L^–1. A tubular electrode, prepared in the same way, may be used as a potentiometric sensor in a flow-injection analysis for Cu (II) and/or iodide determinations. Received: 4 December 1998 / Revised: 31 March 1999 / Accepted: 6 April 1999     

The 4‐(Dimethylamino) benzaldehyde‐4‐ethylthiosemicarbazone as Ionophore for Mercury(II) Solid State Selective Electrode

Hg(II) has formed a soluble complex with 4‐(dimethylamino) benzaldehyde‐4‐ethylthiosemicarbazone (DMABET) in methanol with a molar ratio of mercury(II):DMABET of 1 : 4. The formation constant (K_f) and Gibbs free energy (?G) of the complex showed that the formation of the complex was favorable. The DMABET was investigated as ionophore for Hg(II)‐ion selective electrode (ISE). At optimum pH 1–5 the proposed Hg(II)‐ISE showed an almost Nernstian slope at 27.8±1 mV, with linear regression coefficient, R²=0.995 and a detection limit of 5×10^?6 M. There was no serious interference from silver(I) with selectivity coefficient 5.69×10^?3. The electrode life span was more than 3 months. It has been applied for real water sample analysis and the results were in good agreement with the standard method.     

A Novel Screen-Printed and Carbon Paste Electrodes for Potentiometric Determination of Uranyl(II) Ion in Spiked Water Samples

Four new ion-selective electrodes (ISEs) based on poly-(1-4)-2-amino-2-deoxy-β-D-glucan (chitosan) ionophore were constructed for determination of uranyl ion (UO₂(II)) over wide concentration ranges. The linear concentration range for carbon paste electrodes (CPEs) was 1 × 10^–6–1 × 10^–2 mol/L with a detection limit of 1 × 10^–6 mol/L and that for the screen-printed electrode (SPEs) was 1 × 10^–5–1 × 10^–1 mol/L with a detection limit of 8 × 10^–6 mol/L. The slopes of the calibration graphs were 29.90 ± 0.40 and 29.10 ± 0.60 mV/decade for CPEs with dibutylphthalate (DBP) (electrode I) and o-nitrophenyloctylether (o-NPOE) (electrode II) as plasticizers, respectively. Also, the SPEs showed good potentiometric slopes of 29.70 ± 0.30 and 28.20 ± 1.20 mV/decade with DBP (electrode III) and o-NPOE (electrode IV), respectively. The electrodes showed stable and reproducible potential over a period of 54, 62, 101 and 115 days for electrodes I, II, III, and IV, respectively. The electrodes manifested advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations except Ce(III) ion which interfere seriously. The results obtained compared well with those obtained using atomic absorption spectrometry.     

Mercury ion selective poly(aniline) solid contact electrode based on 2-mercaptobenzimidazol ionophore

A mercury(II) ion selective poly(aniline) solid contact electrode based on 2-mercaptobenzimidazol (2MBI) ionophore as a sulfur containing sensing material was successfully developed. The electrode exhibits a good linear response of 29.1 mV/decade (at 20 ± 0.2°C, r ² = 0.997) within the concentration range of 1 × 10^?2?1 × 10^?7 M Hg(II). The composition of this electrode was: ionophore 0.100, polyvinylchloride (PVC) 0.330, dibutylphthalate (DBP) 0.470, potassiumtetrakis(4-chlorophenyl)borate (KTpCIPB) 0.090, and oleic acid (OA) 0.010. A poly(aniline) solid contact electrode based on 2MBI with DBP and OA plasticizers exhibited the best response characteristics of the results obtained for similarly coated wire type electrodes and solid contact electrodes based on only one DBP plasticizer. The electrode shows good selectivity for mercury(II) ions in comparison with alkali, alkaline earth, transition and heavy metal ions. This electrode is suitable for use with aqueous solutions of pH 3.3?C8.0 and the standard deviation in the measured EMF difference was ±0.5 mV in a mercury nitrate sample solution of 1.0 × 10^?2 M and ±1.1 mV in a mercury nitrate sample solution of 1.0 × 10^?3 M. The stabilization time was less than 15 min and the response time was less than 33 s. The electrode was applied as a sensor for the determination of Hg(II) content in a sea water sample and some amalgam alloys. The results show good correlation with data obtained by atomic absorption spectrometry.     

Cobalt(II) porphyrazine as an active component of iodide-selective electrodes

Cobalt(II) porphyrazine is synthesized and studied as an active component of a polyvinyl chloride plasticized membrane ion-selective electrodes (ISEs). It is established that regardless of their structure, ISEs are sensitive to iodide. The introduction to the ISE of an ionic additive, ionic liquid 1,3-dihexadecylimidazolium chloride, significantly improves the electrochemical characteristics: the slope of the electrode function reaches ?(57 ± 1) mV/dec, c_min = 8.3 × 10^–6 M. Solid-state screen-printed electrodes the surfaces of which are modified by a 1: 4 mixture of cobalt(II) porphyrazine and ionic liquid 1,3-dihexadecylimidazolium chloride demonstrate satisfactory electrochemical characteristics: the slope of the electrode function is ?(56 ± 4) mV/dec and c_min = 2.5 × 10^–5 M. The potentiometric selectivity of the ISEs for iodide is studied. It is found that the effect of lipophilic interfering ions is significantly lower for solid state ISEs than for plasticized membrane electrodes.     

Vermiculite clay mineral as an effective carbon paste electrode modifier for the preconcentration and voltammetric determination of Hg(II) and Ag(I) ions

A vermiculite modified carbon paste electrode (VMCPE) was employed for the in situ preconcentration of traces of Hg(II) and Ag(I) via an ion-exchange route. Heavy metal ions were accumulated in Britton-Robinson (BR) buffer pH 7 for Hg(II) and pH 6 for Ag(I), and afterwards reduced at –0.7 V vs. Ag/AgCl in the separate measurement solution (BR buffer pH 5 + 0.05 mol/L NaNO₃) prior to the anodic stripping square-wave voltammetric (ASSWV) detection. For Hg(II) ions, at 15 min accumulation, a linear range from 1.0 × 10^–7 to 8.0 × 10^–6 mol/L was obtained, with a 5.7 × 10^–8 mol/L limit of detection. The VMCPE response was linear for Ag(I) ions in the concentration range from 2.0 × 10^–7 to 8.0 × 10^–6 mol/L, at 10 min accumulation with a corresponding limit of detection of 6.3 × 10^–8 mol/L. The relative standard deviation of the analytical procedure including accumulation from a 5 × 10^–7 mol/L solution of Hg (15 min) or Ag(I) (10 min), electrolysis, ASSWV detection, regeneration and activation of the VMCPE, was 4% (n = 6). The optimisation of the parameters for the application of the VMCPE in combination with ASSWV detection is presented and discussed. Received: 10 July 1997 / Revised: 31 October 1997 / Accepted: 3 November 1997     

Potentiometric Iodide Selectivity of Polymer‐Membrane Sensors Based on Co(II) Triazole Derivative

The 3‐amion‐5‐mercapto‐1,2,4‐triazole cobalt(II) [Co(II)AMETR] was used as a new carrier for preparing polymeric membrane selective sensor which exhibited high affinity for iodide ion. The effects of membrane composition, pH, the influence of lipophilic ion additives and plasticizer on the response characteristics of the sensor were investigated. The sensor showed a near Nernstian slope of ?56.6 mV/decade for I^? ion over a wide concentration range from 8.5×10^?7 to 1.0×10^?1 M with a low detection limit of 5.1×10^?7 M. The sensor has a fast response time and could be used over a wide pH range of 2–8. The response mechanism is discussed in view of the AC impedance technique. The sensor was successfully applied to direct determination of iodide content in environmental water samples and mouth wash samples.     

Determination of lead (II) ion by highly selective and sensitive lead (II) membrane electrode based on 2-(((E)-2-((E)-1-(2-hydroxyphenyl) methyliden)hydrazono)metyl)phenol

A PVC (poly vinyl chloride) membrane electrode for lead ion based on 2-(((E)-2-((E)-1-(2-hydroxyphenyl)methyliden)hydrazono)metyl)phenol (HMHMP) as a membrane carrier was prepared. This electrode exhibited linear response with Nernstian slope of 29.2?±?0.2?mV per decade within the concentration range of 2.0?×?10^?7–1.0?×?10^?1?M lead ion. The limit of detection, as determined from the intersection of the extrapolated linear segments of the calibration plot, was 8.0?×?10^?8 M. The electrode exhibited high selectivity for Pb (II). The response time of the electrode was about 5–10?s for different concentrations. The electrode is suitable for use in aqueous solutions in a pH range of 5.0–7.5. It was used as an indicator electrode in a titration of Pb (II) with chromate at constant pH. This electrode was used for the determination of lead in ore samples, and the results were in agreement with those obtained with an atomic absorption spectroscopy (AAS) method. Also lead selective electrode was used for monitoring of lead in spiked samples of the Zayanderud River and waste water by the potentiometry technique.     

Potassium ion-selective electrode based on a cobalt(II)-hexacyanoferrate film-modified electrode

A potassium ion-selective electrode based on a cobalt(II)-hexacyanoferrate(III) (CHCF) film-modified glassy carbon electrode is proposed. The electroactive film is introduced onto the glassy carbon electrode surface by electrodeposition of cobalt, which forms a thin CHCF film on subsequent anodic scanning in KClHCl solution (pH 5.0–5.5) containing K₃Fe(CN)₆. The thickness of the film on the electrode surface can be controlled by changing the electrodeposition time and the concentrations of cobalt(II) and Fe(CN)^3?₆ ions. The modified electrode exhibits a linear response in the concentration range 1 × 10^?1 ?3 × 10^?5 M potassium ion activity, with a near-Nernstian slope (48–54 mV per decade) at 25 ± 1°C. The detection limit is 1 × 10^?5 M. The stability, response time and selectivity were investigated. The electrode exhibits good selectivity for potassium ion with the twelve cations investigated. The relative standard deviation is 1.5% (n=10). The effects of the thickness of the electroactive film and the pH of the solution on the electrode response were also investigated.     

Highly Selective Lead(II) Coated Graphite Sensor Based on 4,13-Didecyl-1,7,10,16-tetraoxa-4,13- diazacyclooctadecane as a Neutral Ionophore

4,13-Didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (kryptofix22DD) has been explored as a neutral ionophore for preparing polyvinyl chloride (PVC)-based membrane sensor selective to lead(II). The optimized membrane incorporating kryptofix22DD as the active material, nitrobenzene as plasticizer and sodium tetraphenylborate as an anion excluder and membrane modifier in PVC (in the weight ratio of 5.0: 63.0: 2.0: 30.0, respectively) was directly coated on the surface of graphite rod. The sensor exhibits a Nernstian slope (29.4 mV/decade) in the concentration range of 1.0 × 10^–5 to 1.0 × 10^–1 M Pb²⁺. The detection limit of the sensor is 6.5 × 10^–6 M. The proposed sensor has a fast response time (~10 s), a satisfactory reproducibility and relatively long lifetime. The electrode shows high selectivity toward Pb²⁺ ion in comparison to other common cations. The proposed sensor is suitable for use in aqueous solutions in a wide pH range of 2.0–10.0. It was used as an indicator electrode for the end point detection in the potentiometric titration of Pb²⁺ ion with ethylenediaminetetraacetic acid (EDTA) and sodium iodide (NaI) solutions. The proposed sensor was successfully applied for the recovery of Pb²⁺ ions spiked in real water samples.     

Iodide‐Selective Electrode Based on Copper Phthalocyanine

Copper phthalocyanine was used as ion carrier for preparing polymeric membrane selective sensor for detection of iodide. The electrode was prepared by incorporating the ionophore into plasticized poly(vinyl chloride) (PVC) membrane, coated on the surface of graphite electrode. This novel electrode shows high selectivity for iodide with respect to many common inorganic and organic anions. The effects of membrane composition, pH and the influence of lipophilic cationic and anionic additives and also nature of plasticizer on the response characteristics of the electrode were investigated. A calibration plot with near‐Nernestian slope for iodide was observed over a wide linear range of five decades of concentration (5×10^?6?1×10^?1 M). The electrode has a fast response time, and micro‐molar detection limit (ca. 1×10^?6 M iodide) and could be used over a wide pH range of 3.0–8.0. Application of the electrode to the potentiometric titration of iodide ion with silver nitrate is reported. This sensor is used for determination of the minute amounts of iodide in lake water samples.     

Construction of Suitable Iodide–Selective Electrode Based on Phenyl Mercury (II)(2‐mercaptobezothiozolate) Carrier

Abstract

Highly selective poly(vinyl chloride) (PVC) membrane electrode based on recently synthesized mercury complex i.e., phenyl mercury (II) (2‐mercaptobezothiozolate) (PMMBT) as new carrier for iodide‐selective electrode by incorporating the membrane ingredients on the surface of graphite electrode are reported. The effect of various parameters including the membrane composition, pH, and possible interfering anions were investigated on the response properties of the electrode. The developed sensor exhibited Nernstian responses toward iodide over a wide concentration range of 1×10^?7 to 0.1 M with slopes of 57.6±0.8 mV per decade of iodide concentration and detection limit of 8×10^?8 M, over a wide pH ranges of 2.0–11.5. The sensors have response time of 0.5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrode show good ability to discriminate iodide over several inorganic and organic anions.

The electrode was successfully applied to direct determination of iodide in synthetic mixture, waste water and drinking water, and pharmaceutical samples in addition to applying as indicator electrode in precipitation titration.     

Thiocyanate-selective electrode based on cobalt(II) complexes of pyrazolone heterocyclic Schiff bases

A new solvent polymeric membrane electrode based on pyrazolone heterocyclic Schiff base complexes of Co(II) is described. It shows a preferential response towards thiocyanate over a range of 2.0 × 10^–6 to 1.0 × 10^–1 mol L^–1 with a slope of –60.2 ± 0.6 mV/dec. The selectivity sequence observed is thiocyanate > hydroxide > nitrite > iodide > perchlorate > citrate > bromide > fluoride > chloride > nitrate > acetate > borate > sulfate > phosphate. The selectivity behavior is discussed in view of axial coordination by uv/vis spectroscopy and the transfer process of thiocyanate across the membrane interface is investigated by the ac impedance technique. The electrode was successfully applied to the determination of thiocyanate in human urine as an indicator for distinguishing between smokers and non-smokers.