Solid-state Cu (II) ion-selective electrode based on polyaniline-conducting polymer film doped with copper carmoisine dye complex

A pencil graphite electrode coated by copper (II)–carmoisine dye complex in polyaniline (emeraldine base form) matrix (termed as PGE/PA/Cu-Car) was prepared and used as copper ion-selective electrode. The introduced electrode was found to have high selectivity toward copper ion (II) and exhibited wide working concentration range, low response time, and good shelf life. The sensor electrode showed a linear Nernstian response over the range of 5.0 × 10⁻⁶ to 1.0 × 10⁻¹ M with a slope of 29.7 ± 1 mV per decade change in concentration. A detection limit of 2.0 × 10⁻⁶ M was obtained. The optimum pH working range of the electrode was found to be 4.0–7.0.     

Subnanomolar determination of a beryllium ion by a novel Be(II) microsensor based on 4-nitrobenzo-9-crown-3-ether

In this work, for the first time, we introduce a highly selective and sensitive Be(II) microsensor. 4-nitrobenzo-9-crown-3-ether (NBCE) was used as a membrane-active component to prepare a Be(II)-selective polymeric membrane microelectrode. The electrode exhibits a Nernstian response toward Be(II) ions over a very wide concentration range (1.0 × 10⁻⁴–1.0 × 10⁻¹⁰ M), with a detection limit of 3.5 × 10⁻¹¹ M (∼350 pg/L). In fact, the electrode presents a fast response time in the whole concentration range (6 s). The proposed microelectrode can be used for at least six weeks without any considerable divergence in the potentials. The proposed membrane sensor revealed a selectivity toward Be(II) ions over a wide variety of other metal ions including common alkali, alkaline-earth, and rare-earth ions. It could be used in the pH range of 3.0–11.5. The microelectrode was successfully used as an indicator electrode for the titration of 20 mL of 1.0 × 10⁻⁶ M Be²⁺ solution with 1.0 × 10⁻⁴ M of EDTA. It was also applied to the direct determination of beryllium ions in beryl and binary mixtures. The text was submitted by the authors in English.     

Electrochemical detection of copper(II) at a gold electrode modified with a self-assembled monolayer of penicillamine

A penicillamine (PCA) self-assembled monolayer (SAM) was prepared on a gold electrode. It has been found that the modified electrode exhibited a selective response to copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to preconcentrate efficiently traces of copper(II) from solutions. Under optimum conditions, the anodic peak current was proportional to the concentration of Cu(II) in the range from 8.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M with a detection limit of 4.0 × 10⁻⁷ M. Moreover, this modified gold electrode is also characterized by excellent repeatability, showing a relative standard deviation of 3.2% for nine successive measurements of 1.0 × 10⁻⁵ M Cu(II). The PCA/Au SAM gold electrode was used for the determination of Cu(II) in a tap water sample and the results showed a good agreement with the data obtained by atomic emission spectrometry. The text was submitted by the authors in English.     

PVC-based Cu (II)-Schiff base complex membrane coated graphite electrode for the determination of the triiodide ion

A triiodide-selective electrode based on copper (II)-Schiff base complex as a membrane carrier is proposed. The electrode was prepared by incorporating the carrier into a plasticized polyvinylchloride (PVC) membrane and was directly coated on the surface of a graphite electrode. The obtained electrode showed a near Nernstian slope of 57.0 ± 0.4 mV/decade to I ₃ ⁻ ions over an activity range of 1.0 × 10⁻⁵−1.0 × 10⁻¹ M with a limit of detection of 4.8 × 10⁻⁶ M. The response time of the electrode was fast (5 s) and the electrode could be used for about 2 months without considerable divergence in response. The potentiometric selectivity coefficients were evaluated and displayed anti-Hofmeister behavior. The electrode was used as an indicator electrode in the potentiometric titration of the triiodide ion and in the determination of ascorbic acid in vitamin C tablets. The text was submitted by the authors in English.     

A novel chemically modified carbon paste electrode based on a new mercury(II) complex for selective potentiometric determination of bromide ion

A new modified carbon paste electrode based on a recently synthesized mercury (II) complex of a pyridine containing proton transfer compound as a suitable carrier for Br⁻ ion is described. The electrode has a linear dynamic range between 3.00×10⁻² and 1.0×10⁻⁵ M with a near-Nernastian slope of 61.0±0.9 mV per decade and a detection limit of 4.0×10⁻⁶ M (0.32 ppm). The potentiometric response is independent of the pH of the solution in the pH range 4.0–8.3. The electrode possesses the advantages of low resistance, fast response and good over a variety of other anions. It was applied as an indicator electrode in potentiometric titration of bromide ions and for the recovery of Br⁻ from tap water.     

Cobalt(II) ion-selective electrode with solid contact

A new all plastic sensor for Co²⁺ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10⁻⁶ mol L⁻¹ and almost theoretical Nernstian slope in the activity range 4.0 × 10⁻⁶–1 × 10⁻¹ mol L⁻¹ of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co²⁺ in real samples and as an indicator electrode in potentiometric titration of Co²⁺ ions with EDTA.      

The complex (2,3;6,7;10,11;14,15-tetraphenyl-4,9,13,16-tetraoxo-1,5,8,12-tetraazacyclohexadecane) copper(II) as a carrier for a salicylate-sensitive poly(vinylchloride) membrane electrode

A new salicylate-selective electrode based on the complex (2,3;6,7;10,11;14,15-tetraphenyl-4,9,13,16-tetraoxo-1,5,8,12-tetraazacyclohexadecane) copper(II) [CuL] as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of −60.9 ± 1.0 mV/decade and a linear range from 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ M for salicylate. The detection limit is 5.0 × 10⁻⁷ M. The electrode has a fast response time (5–15 s) and can be used for more than three months. The selective coefficients were determined by the fixed interference method (FIM) and separate solution method (SSM). The salicylate-selective electrode could be used in the pH range 3.5–10.5. It was employed as an indicator electrode for direct determination of salicylate in pharmaceutical samples. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 9, pp. 1147–1154. The text was submitted by the authors in English.     

Thiocyanate-selective electrode based on N-salicylidene-benzylamineato copper(II) complex

Highly selective poly(vinyl chloride) (PVC) membrane electrode based on N-salicylidene-benzylamineato copper(II) complexes [Cu(SBA)₂] as new carriers towards thiocyanate-selective electrode was reported. The influence of membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. The resulting electrode exhibits anti-Hofmeister selectivity sequence: SCN⁻ > ClO₄⁻ > Sal⁻ > I⁻ > Br⁻ > NO₃⁻ > NO₂⁻ > SO₃²⁻ > H₂PO₄⁻ > Cl⁻ > SO₄²⁻, and a near-Nernstian potential linear range for thiocyanate from 1.0 × 10⁻¹ to 9.0 × 10⁻⁷ M with a detection limit of 7.0 10⁻⁷ M and a slope of , over a wide pH range of 3.0–9.0 in phosphate buffer solution at 20°C. The proposed electrode has a fast response time of about 5–10 s and can be used for at least 3 months without any considerable divergence in potential. The electrode was successfully applied to the determination of thiocyanate in waste water and human urine and saliva samples. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 3, pp. 293–299. The text was submitted by the authors in English.     

Copper(II) ion selective electrode based on a newly synthesized Schiff-base chelate

A new Cu (II) ion-selective electrode has been fabricated in poly (vinyl chloride) matrix based on a recently synthesized Schiff-base chelate. The addition of sodium tetraphenylborate (NaTPB) and various plasticizers viz. TBP, TEHP, DOS, and CN have been found to substantially improve the performance of the electrode. The membrane of various compositions of the ionophore (I) were investigated and it was found that the best performance was obtained with the membrane having (I): PVC: NaTPB: CN in the ratio 4: 140: 3: 80 (mg). The electrode exhibits a Nernstian response over a wide concentration range (1.9 × 10⁻⁶–1.0 × 10⁻¹ M) with 30.0 mV/decade of concentration between pH 3.0 and 7.5. The response time of the electrode is about 12 s and it can be used over a period of 3 months without any divergence in potential. The potentiometric selectivity coefficient values as determined by fixed interference method indicate excellent selectivity for Cu²⁺ ions over interfering cations. The electrode has also been used successfully in partially non-aqueous media having a 25% (v/v) methanol, ethanol or acetone content without showing any considerable change in the value of slope or working concentration range. The electrode has been used in the potentiometric titration of Cu²⁺ with EDTA.     

Aluminium(III)-selective electrode based on a newly synthesized glyoxal-<Emphasis Type="Italic">bis</Emphasis>-thiosemicarbazone Schiff base

A PVC membrane electrode for Al³⁺ based on glyoxal-bis-thiosemicarbazone (GBTC) as an ion carrier was developed. The electrode exhibits a Nernstian slope of 20.1 mV per decade and a linear range of 1.8 × 10⁻⁵−1.0 × 10⁻¹ M for Al(NO₃)₃ with a detection limit of 8.7 × 10⁻⁶ M. It has a fast response time of about 10 s and can be used for at least 1 month. The proposed membrane sensor revealed a good selectivity for Al³⁺ over a wide variety of other metal ions and could be used in the pH range of 2.5–4.5. The text was submitted by the authors in English.     

A novel lariat crown compound as ionophore for construction of a mercury(II)-selective electrode

Abstract  

The construction, performance, and application of a new PVC membrane electrode for determination of the mercury(II) ion, based on 8,17-bis(pyren-1-ylmethyl)-6,7,8,9,15,16,17,18-octahydrodibenzo[f,m][1,8,4,11]dithiadiazacyclotetradecine as an ionophore, is described. The effects of factors such as membrane composition, the nature and amount of the plasticizers and additives, and pH for the improved sensitivity of the electrode were studied. The electrode had a Nernstian response for mercury(II) ions over the concentration range 1.0 × 10⁻²–1.0 × 10⁻⁶ mol dm⁻³ with a slope of 27.6 ± 0.6 mV/pHg. The detection limit for mercury(II) was 7.9 × 10⁻⁷ mol dm⁻³. The response time of the electrode was between 5 and 15 s, depending on the concentration of mercury, and it can be used in a pH range 4.0–4.5 for approximately 4 months without any substantial divergence of the response characteristics. It showed higher selectivity for mercury(II) ions than for several common alkali, alkaline earth, and transition metal ions except silver(I). The proposed electrode was successfully applied to direct determination of mercury in a dental filling amalgam alloy as a real sample with a complex matrix and as an indicator electrode in complexation titrations.     

Determination of thiocyanate ions at nanolevel in real samples using coated graphite electrode based on synthesised macrocyclic Zn(II) complex

The electrode characteristics and selectivities of PVC-based thiocyanate selective polymeric membrane electrode (PME) incorporating the newly synthesized zinc complex of 6,7:14,15-Bzo₂-10,11-(4-methylbenzene)-[15]-6,8,12,14-tetraene-9,12-N₂-1,5-O₂ (I ₁ ) and zinc complex of 6,7:14,15-Bzo₂-10,11-(4-methylbenzene)-[15]-6,14-diene-9,12-dimethylacrylate-9,12-N₂-1,5-O₂ (I ₂ ) are reported here. The best response was observed with the membrane having a composition of I₂:PVC:o-NPOE:HTAB in the ratio of 6:33:59:2 (w/w; milligram). This electrode exhibited Nernstian slope for thiocyanate ions over working concentration range of 4.4 × 10⁻⁷ to 1.0 × 10⁻² mol L⁻¹ with detection limit of 2.2 × 10⁻⁷ mol L⁻¹. The performance of this electrode was compared with coated graphite electrode (CGE), which showed better response characteristics w.r.t Nernstian slope 59.0 ± 0.2 mV decade⁻¹ activity, wide concentration range of 8.9 × 10⁻⁸ to 1.0 × 10⁻² mol L⁻¹ and detection limit of 6.7 × 10⁻⁸ mol L⁻¹. The response time for CGE and PME was found to be 8 and 10 s, respectively. The proposed electrode (CGE) was successfully applied to direct determination of thiocyanate in biological and environmental samples and also as indicator electrode in potentiometric titration of SCN⁻ ion.     

Construction of different types of ion-selective electrodes and validation of direct potentiometric determination of phenytoin sodium

The construction and performance characteristics of phenytoin sodium selective electrodes are detailed. Two types of electrodes: plastic membrane I and coated wire II, were constructed based on the incorporation of phenytoin sodium with tungstosilicic acid. The influence of membrane composition, kind of plasticizer, pH of the test solution, soaking time and the electrodes’ foreign ions were investigated. The electrodes showed a Nernstian response with a mean calibration graph slope of 30.9±0.1 and 28.9±0.1 mV decade⁻¹ at 25°C for electrode I and II respectively, over a phenytoin sodium concentration range of 5×10⁻³−5×10⁻⁶ M and 1×10⁻³−1×10⁻⁶ M with a detection limit 1.3×10⁻⁶ M and 2.5×10⁻⁷ M for electrode I and II, respectively. The electrodes gave average selective precision and were usable within the pH range 6–10. Interference studies from common cations, alkaloids, sugars, amino acids and drug excipients are reported. The results obtained by the proposed electrodes were also applied successfully for the determination of the drug in pharmaceutical preparations and biological fluids.     

Iodide ion selective poly(aniline) solid contact electrode based on quinine-cu ionophores

Iodide ion selective poly(aniline) solid contact electrode based on quinine-Cu ionophore as a sensing material has been successfully developed. The electrode exhibits good linear response of 52.0 mV/decade (at 20 ± 0.2°C, r ² = 0.9998) within the concentration range of 1 × 10^−6.4–1 × 10^−1.0 M KI. The composition of this electrode was quinine-Cu 2.0: PVC 30.0: bis(2-ethylhexyl)sebacate 68.0 (mass). This plasticizer provides the best response characteristics. The electrode shows good selectivity for iodide ion in comparison with any other anions and is suitable for use with aqueous solutions of pH 3.3–9.4. The standard deviations of the measured EMF difference were ±1.4 and ±1.3 mV for iodide sample solutions of 1.0 × 10⁻² M and 1.0 × 10⁻³ M, respectively. The stabilization time was less than 10 min and response time was less than 15 sec.     

Differential pulse polarographic determination of Co(II) using moxifloxacine

The polarographic reduction of Co(II) in the presence of moxifloxacin (1-cyclopropyl-7-[(S,S)-2.8-diazabicyclo[4.3.0]non-8-yl]-6-fluoro-8-methoxy-1.4-dihydro-4-oxo-3-quinolinecarboxylic acid) gives rise to an additional adsorption peak corresponding to the reduction of Co(II)-moxifloxacin complex on the mercury drop electrode at −1.17 V. This new peak is applicable to Co(II) determination with the linearity proportional to the Co(II) concentration in the range of 4.93 × 10⁻⁷−6.90 × 10⁻⁵ M and can be attributed to an adsorption-controlled process with an irreversible reduction. Without using moxifloxacin, the polarographic determination of 2.50 × 10⁻⁶ M Co(II) is impossible under the given conditions due to very poor sensitivity at −1.38 V. The proposed method showed good precision and accuracy with a relative standard deviation of 3.01% and relative error of +6.40% for the determination of 2.50 × 10⁻⁶ M Co(II) next to 5.0 × 10⁻⁶ M of Zn(II), Ni(II), and Cd(II). The accuracy of the method was also checked by the determination of Co(II) spiked with tap water and certified sea water, and the percentage recoveries were 97.5 and 96.7%, respectively (n = 4 at 95% confidence interval). The text was submitted by the authors in English.     

Cobalt(II)-selective membrane sensor based on a [Me2(13)dieneN4] macrocyclic cobalt complex

A new poly(vinyl chloride)-based membrane was fabricated with the cobalt(II) complex of 2,4-dimethyl-1,5,8,11-tetraazacyclotrideca-1,4-diene [Me₂(13)dieneN₄] as an ion carrier. The membrane composition was Co²⁺ complex/PVC/NaTPB/DBP 15:50:15:20 (w/w). The sensor exhibited a Nernstian response for Co²⁺ ions over a wide concentration range (7.94×10⁻⁶–1.0×10⁻¹ M) at pH 2.5–7.0, a response time of 10 s, and it could be used for 3 months without any significant divergence in potential. The proposed membrane sensor exhibited good selectivity for Co²⁺ over a wide variety of other metal ions and in mixtures containing up to 25% (v/v) non-aqueous content. The sensor was successfully used as an indicator electrode in the potentiometric titration of Co²⁺ with EDTA and the direct determination of Co²⁺ in real samples.     

Anodic stripping voltammetric determination of silver(I) in water using a 4-tert-butyl-1(ethoxycarbonylmethoxy)thiacalix[4]arene modified glassy carbon electrode

A glassy carbon electrode coated with film of 4-tert-butyl-1-(ethoxycarbonylmethoxy)thiacalix[4]arene is designed for the determination of trace amounts of Ag⁺. Compared with bare glassy carbon electrode, the modified electrode can greatly improve the measuring sensitivity for Ag⁺. Under the optimum experimental conditions, the modified electrode in B-R buffer solution (pH 4.5) shows a linear voltammetric response in the range of 5.0 × 10⁻⁸–3.0 × 10⁻⁶ M with detection limit 1.0 × 10⁻⁸ M for Ag⁺. The high sensitivity, selectivity, and stability of modified electrode also demonstrate its practical application for a simple, rapid and economical determination of Ag⁺ in water samples.     

Application of a trazodone-selective electrode to pharmaceutical quality control and urine analyses

A trazodone-selective electrode for application in pharmaceutical quality control and urine analysis was developed. The electrode is based on incorporation of a trazodone-tetraphenylborate ion exchanger in a poly(vinyl chloride) membrane. The electrode showed a fast, stable and Nernstian response over a wide trazodone concentration range (5 × 10⁻⁵−1 × 10⁻² M) with a mean slope of 59.3 ± 0.9 mV/dec of concentration, a mean detection limit of 1.8 × 10⁻⁵± 2.2 × 10⁻⁶ M, a wide working pH range (5–7.5) and a fast response time (less than 20 s). The electrode also showed good accuracy, repeatability, reproducibility and selectivity with respect to some inorganic and organic compounds, including the main trazodone metabolite. The electrode provided good analytical results in the determination of trazodone in pharmaceuticals and spiked urine samples; no extraction steps were necessary. Dissolution testing of trazodone tablets, in different conditions of pH and particle size, based on a direct potentiometric determination with the new selective electrode is presented as well.     

Catalytic adsorptive stripping voltammetric determination of copper(II) on a carbon paste electrode

A catalytic adsorptive stripping voltammetric method for the determination of copper(II) on a carbon paste electrode (PCE) in an alizarin red S (ARS)-K₂S₂O₈ system is proposed. In this method, copper(II) is effectively enriched by both the formation and adsorption of a copper(II)-ARS complex on the PCE, and is determined by catalytic stripping voltammetry. The catalytic enhancement of the cathodic stripping current of the Cu(II) in the complex results from a redox cycle consisting of electrochemical reduction of Cu(II) ion in the complex and subsequent chemical oxidation of the Cu(II) reduction product by persulfate, which reduces the contamination of the working electrode from Cu deposition and also improves analytical sensitivity. In Britton-Robinson buffer (pH 4.56±0.1) containing 3.6×10⁻⁵ mol L⁻¹ ARS and 1.6×10⁻³ mol L⁻¹ K₂S₂O₈, with 180 s of accumulation at −0.2 V, the second-order derivative peak current of the catalytic stripping wave was proportional to the copper(II) concentration in the range of 8.0×10⁻¹⁰ to ∼3.0×10⁻⁸ mol L⁻¹. The detection limit was 1.6×10⁻¹⁰ mol L⁻¹. The proposed method was evaluated by analyzing copper in water and soil.     

Fabrication of an iron(III)-selective PVC membrane sensor based on a bis-bidentate Schiff base ionophore

A Fe³⁺ ion-selective membrane sensor was fabricated from polyvinyl chloride (PVC) matrix membrane containing bis-bidentate Schiff base (BBS) as a neutral carrier, sodium tetraphenyl borate (NaTPB) as anionic excluder, and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The effects of the membrane composition, pH, and additive anionic influence on the response properties were investigated. The best performance was obtained with a membrane containing 32% PVC, 62.5% NPOE, 3% BBS, and 2.5% NaTPB. The electrode shows a Nernstian behavior (slope of 19.3 ± 0.6) over a very wide iron ion concentration range (1.0 × 10⁻⁷–1.0 × 10⁻² M) and has a low detection limit (7.4 × 10⁻⁸ M). The potentiometric response of the sensor is independent of pH of the solution in the pH range 1.9–5.1. The proposed sensor has a very low response time (<15 s) and a good selectivity relative to a wide variety of other metal ions including common alkali, alkaline earth, heavy, and transition metal ions. The electrode can be used for at least 60 days without any considerable divergence in potentials. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of 1.0 × 10⁻² M Fe³⁺ ions with a 1.0 × 10⁻⁴ M EDTA and the direct determination of Fe³⁺ in mineral water and wastewater samples.