Selective Membrane Electrode Research Articles

A New Selective Membrane Electrode for Oxalate Based on N,N'-Bis(salicylidene)-2,2-dimethylpropane-1,3-diamine Ni(II)

A new solvent polymeric membrane electrode, based on N,N'-bis(salicylidene)-2,2-dimethylpropane-1,3diamine Ni(II) as the ionophore, was designed. The oxalate-selective electrode has the dynamic range between 1.0 × 10 −6 M and 1.0 × 10 −1 M with a Nernstian slope of −28.7 ± 1.0 mV per decade. The detection limit was 6.3 × 10 −7 M. The proposed electrode revealed good selectivities for oxalate over a variety of other anions and could be used in a pH range of 2.0-7.8. The electrode can be used for at least two months without any considerable divergence in potential. The designed electrode was applied as an indicator electrode in the potentiometric determination of oxalate in real samples.

The Composition Dependence Selectivity Changes by Plasticizer at the Cation Sensors Based on Tetracycline Antibiotics

The performances of tetracycline based cation selective polymeric membrane electrodes of many sets with different plasticizers were investigated as the selectivity of ion-selective electrodes and optodes are greatly influenced by membrane solvent and also controlled by plasticizers. The membrane 1 with Bis(2-ethylhexyl) sebacate (DOS) and additive shows good potentiometric performance toward Ca2+ (slope: 27.8 mV per decade; DL: -4.52) including selectivity. Contrastingly, membrane 4 with Dibutyl phthalate (DBP) shows near-Nernstian response, it has also shown the best measuring range and detection limit for Ca2+ (29.5 mV and -5.10) and Mg2+ (24.4 mV and -5.04) and the least selectivity has been also observed between Ca2+ and Mg2+. When the membrane 1 and 4 were used together to flow system, we could determine the concentration of Ca2+ and Mg2+, simultaneously.

Aptamer-Based Potentiometric Measurements of Proteins Using Ion-Selective Microelectrodes

We here report on the first example of an aptamer-based potentiometric sandwich assay of proteins. The measurements are based on CdS quantum dot labels of the secondary aptamer, which were determined with a novel solid-contact Cd2+-selective polymer membrane electrode after dissolution with hydrogen peroxide. The electrode exhibited cadmium ion detection limits of 100 pM in 100 mL samples and of 1 nM in 200 microL microwells, using a calcium-selective electrode as a pseudoreference electrode. As a prototype example, thrombin was measured in 200 microL samples with a lower detection limit of 0.14 nM corresponding to 28 fmol of analyte. The results show great promise for the potentiometric determination of proteins at very low concentrations in microliter samples.

Application of the cobaltabisdicarbollide anion to the development of ion selective PVC membrane electrodes for tuberculosis drug analysis

The cobaltabisdicarbollide anion is used as a new material able to generate an ion-pair complex used for PVC membrane ion selective electrodes.

A fast response hafnium selective polymeric membrane electrode based on N, N′-bis(α-methyl-salicylidene)-dipropylenetriamine as a neutral carrier

In this study a new hafnium selective sensor was fabricated from polyvinylchloride (PVC) matrix membrane containing neutral carrier N, N′-bis(α-methyl-salicylidene)-dipropylenetriamine (Mesaldpt) as a new ionophore, sodium tetraphenyl borate (NaTPB) as anionic discriminator and dioctyl phthalate (DOP) as plasticizing solvent mediator in tetrahydrofuran solvent. The electrode exhibits Nernstian response for Hf 4+ (Hafnium(IV)) over a wide concentration range (2.0 × 10 −7 to 1.0 × 10 −1 M) with the determination coefficient of 0.9966 and slope of 15.1 ± 0.1 mV decades −1. The limit of detection is 1.9 × 10 −7 M. The electrode has a fast response time of 18 s and a working pH range of 4–8. The proposed membrane shows excellent discriminating ability towards Hf 4+ ion with regard to several alkali, alkaline earth transition and heavy metal ions. It can be used over a period of 1.5 months with good reproducibility. It is successfully applied for direct determination of Hf 4+ in solutions by standard addition method for real sample analysis.

고 선택성 수은(II) 이온 막 센서

A new ion selective PVC membrane electrode is developed as a sensor for mercury(II) ions based on bis(benzoylacetone) propylenediimine (H 2 (BA) 2 PD) as an ionophore. The electrode shows good response characteristics and displays, a linear Emf vs. log[Hg 2+ ] response over the concentration range of 1.0×10 -6 to 1.0×10 -1 M Hg(II) with a Nemstian slope of 29.8±0.75 mV per decade and with a detection limit of 2.2×10 -7 M Hg(II) over the pH range of 2.5-11.5. Selectivity concentrations for Hg(II) relative to a number of potential interfering ions were also investigated. The sensor is highly selective for Hg(II) ions over a large number of cations with different charge. The sensor has been found to be chemically inert showing a fast response time of 60 s and was used over a period of 3 months with a good reproducibility (S = 0.27 mV). The electrode was successfully applied to determine mercury(II) in real samples with satisfactory results.

Flow injection potentiometry by a novel coated graphite electrode based on 5-(9-anthracenylmethyl)-5-aza-2,8-dithia[9],(2,9)-1,10-phenanthrolinophane for the selective determination of uranyl ions

Abstract Spectrofluorimetric studies on the binding properties of 5-(9-anthracenylmethyl)-5-aza-2,8-dithia[9],(2,9)-1,10-phenanthrolinophane (L) toward different heavy metal ions in methanol solution revealed its selective 2:1 (ligand/metal) complexation with uranyl ion. Consequently, L was used as a suitable ionophore for the preparation of new plasticized PVC membrane-selective electrodes for the determination of uranyl ion by flow injection potentiometry. The electrodes resulted in Nernstian responses for UO22+ ion over wide concentration ranges (1.0 × 10−6 to 1.0 × 10−1 M with a detection limit of 8.3 × 10−7 M for polymeric membrane electrode, PME, and 1.0 × 10−7 to 1.0 × 10−1 M with a detection limit of 7.5 × 10−8 M for coated graphite electrode, CGE). The potentiometric response is independent of the pH of test solution in the pH range 2.5–4.0. The proposed electrodes possess very good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The CGE was used in flow injection potentiometry and resulted in well defined peaks for uranyl ions with stable baseline, excellent reproducibility and very high sampling rate of 160 injections h−1. The proposed FIP system was used for the determination of trace uranyl ions in real and synthetic samples.

Selective membrane electrode assemblies for bipolar plate-free mixed-reactant fuel cells

Membrane electrode assemblies (MEAs) with PtRu/C and Pt/C as both sides electrocatalysts have been fabricated and used in a mixed-reactant alkaline fuel cell without bipolar plate. It has been found that the reactant selectivity of the electrocatalyst is tunable by changing the electrode hydrophobicity. The measurement on a three-cell stack with MEAs using a more hydrophobic PtRu/C electrode and a more hydrophilic Pt/C electrode in an ethanol/oxygen mixed solution shows that the PtRu/C electrode serves as a cathode and Pt/C electrode performs as an anode. The steady-state power density of 31 mW cm −2 is achieved in an ethanol solution by continuously bubbling oxygen at ambient temperature and atmosphere pressure.

Highly selective and sensitive copper membrane electrode based on a new synthesized Schiff base

Bis(2-hydroxyacetophenone)butane-2,3-dihydrazone (BHAB) was used as new N-N Schiffs base which plays the role of an excellent ion carrier in the construction of a Cu(II) membrane sensor. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 55% o-nitrophenyloctyl ether (NPOE), 7% BHAB and 8% oleic acid (OA). This sensor shows very good selectivity and sensitivity towards copper ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition and pH and influence of additive anionic on the response properties of electrode were investigated. The electrode exhibits a Nernstian behavior (with slope of 29.6 mV per decade) over a very wide concentration range (5.0 × 10 −8 to 1.0 × 10 −2 mol L −1) with a detection limit of 3.0 × 10 −8 mol L −1 (2.56 ng mL −1). It shows relatively fast response time, in whole concentration range (<15 s), and can be used for at least 12 weeks in the pH range of 2.8–5.8. The proposed sensor was successfully used to determination of copper in different water samples and as indicator electrode in potentiometric titration of copper ion with EDTA.

A Highly Selective and Sensitive Thorium(IV) PVC Membrane Electrode Based on a Dithio-tetraaza Macrocyclic Compound

A poly(vinyl chloride)-based membrane composed of dithio-tetraaza macrocyclic compound as a neutral carrier with sodium tetraphenylborate (NaTPB) as an anion excluder and nitrobenzene (NB) as plasticizer was prepared and investigated as a Th(IV)-selective electrode. The electrode exhibits a Nernstian slope of 14.2 +/- 0.3 mV per decade over a wide concentration range (1.0 x 10(-6) to 1.0 x 10(-1) M) with a detection limit of 8.0 x 10(-7) M between pH 3.5 and 9.5. The response time of the sensor is about 10 s and it can be used over a period of 5 months without any divergence in potential. The proposed membrane sensor revealed a good selectivity for Th(IV) over a wide variety of other metal ions and proved to be a better electrode in many respects than those reported in the literature. It was successfully applied as an electrode indicator as well as in the direct determination of thorium ions in standard and real samples.

Batch and Flow‐Injection Determination of Catecholamines Using Ion Selective Electrodes

New epinephrine (EP), dopamine (DA), and L‐Dopa (LD) ion selective PVC membrane electrodes based on ion‐pairs of catecholamines with tetraphenylborate (TPhB) are prepared. In the present work, plastic membrane selective electrodes have been constructed. They are based on the incorporation of EP‐TPhB, DA‐TPhB, or LD‐TPhB ion exchangers in poly(vinylchloride) (PVC) membranes plasticized with di(2‐ethylhexyl)sebacate (DES). The electrodes show a near – Nernstian response in the concentration ranges: 1.0×10−4—1.0×10−2 mol/L (epinephrine), 5.0×10−5–1.0×10−2 mol/L (dopamine), and 5.0×10−4–1.0×10−2 mol/L (L‐Dopa). The electrodes selective for epinephrine and L‐Dopa are used as detectors in the flow injection system. The proposed methods allow determination of catecholamines in pharmaceutical preparations.

Novel Copper(II)‐Selective Membrane Electrode Based on a New Synthesized Schiff Base

AbstractA PVC membrane electrode for copper(II) ion based on a recently synthesized Schiff base as a suitable ion carrier was constructed. The electrode exhibits a Nernstian slope of 28.3 ± 0.6 mV per decade of Cu2+ over a wide concentration range of 7.0 × 10−6‐2.6 × 10−2 M with a detection limit of 5.0 × 10−6M in the pH range of 4.2–5.8. The response time is about 10s and it can be used for at least 1 month without any considerable divergence in potential. It was successfully applied as an indicator electrode in the potentiometric titration of copper ions.

A New Tiapride Selective Electrode and Its Clinical Application

The construction and electrochemical response characteristics of a poly(vinylchloride) (PVC) membrane selective electrode for the determination of tiapride (TPD) are described. The sensing membrane comprised an ion-pair formed between the protonated drug and tetraphenylborate (TPB-) in a plasticized PVC matrix. The influence of membrane composition on the electrode response was studied. The electrode showed a fast, stable and Nernstian response over a wide tiapride concentration range (1x10-5-1x10-2 M) with a slope of 57.5±0.2 mV dec-1 of concentration, a detection limit of 4.3x10-6±2.5x10-7 M, a wide working pH range (2-8) and a fast response time (&lt; 5 s). The electrode showed good selectivity towards tiapride with respect to some inorganic and organic compounds. The electrode has been applied to the determination of tiapride in human urine and iontophoresis solution.

Study of interaction between Aspergillus niger cellulase (ANC) and Cetyltrimethylammonium Bromide (CTAB) using surfactant membrane selective electrode

The interaction of cetyltrimethylammonium bromide, CTAB, to Aspergillus niger cellulase, ANC, has been studied using potentiometric technique. Binding isotherms were obtained from the potentiometric technique and using the Wyman binding potential model, apparent binding constants were calculated. The obtained binding isotherms have been analysed and interpreted using the Wyman binding potential. The Gibbs free energy change calculated on the basis of the Wyman binding potential concept decreases with increasing amount of binding. The affinity of binding increased with increasing temperature, indicating an endothermic and essentially entropy driven process. On the other hand, studying of binding processes at various pH indicates that ANC has a more enthalpic stability and probably has a more packed structure at pH = 5 than that at pH = 7.5 and 10. Data analysis based on the Scatchard equation at various pH and temperatures shows a linear behavior with positive slope, indicating one set of binding sites.

Mercury (II) - Selective PVC Membrane Electrodes Based on Novel Cryptand Derivatives

Mercury (II) - Selective PVC Membrane Electrodes Based on Novel Cryptand Derivatives

Copper (Il)-Selective Membrane Electrodes Based on Cu (Il)-Schiff Base Complexes as an Ionophore

Copper (Il)-Selective Membrane Electrodes Based on Cu (Il)-Schiff Base Complexes as an Ionophore

Binding and fluorescence study on interaction of human serum albumin (HSA) with cetylpyridinium chloride (CPC)

Human serum albumin (HSA) is frequently used in biophysical and biochemical studies since it has a well-known primary structure and it has been associated with the binding of many different categories of small molecules. In the present study, results are presented for the binding of cetylpyridinium chloride (CPC) with HSA at various pH and 25 °C, as monitored using ion selective membrane electrodes and fluorescence spectroscopy of intrinsic tryptophan. The obtained binding isotherms were analyzed on basis of binding capacity concept and Hill plot in order to determine the Hill parameters of binding sets. The system behaved as a system with two sets of binding sites in all studied situations. The results represent a positive cooperative behavior and the essential role of hydrophobic interactions in both binding sets. The intrinsic binding affinity of second binding set have a similar values and trends at acidic and neutral pHs, that represents the similar unfolded structure at these pHs. CPC quenched the fluorescence arising from Trp group incorporated to HSA. A biphasic behavior was observed in quenching process that confirmed the results of binding study correspond to the existence of two binding sets. The similarity of unfolded structure in acidic and neutral pH was also confirmed by fluorescence study. The quenching of HSA fluorescence takes place with a Stern–Volmer constant of 0.643 × 10 4, 1.23 × 10 4 and 7.40 × 10 4 at pH 3.5, 6.8 and 9.5, respectively. The Stern–Volmer behavior observed at low molar ratio of [CPC]/[HSA] (about 6), that represents the occurrence of conformational changes after this molar ratio. Comparing, the K SV values and binding parameters indicate that the binding is dominated by hydrophobic effects and, in minor degree, by electrostatic interactions.

A novel iron(III) selective membrane electrode based on benzo-18-crown-6 crown ether and its applications

A new membrane electrode selective to iron(III) (in FeCl 4 − structure) has been developed based on crown ether. The electrode consisted of trans-dinitro-dibenzo-18-6 crown ether as a neutral carrier, 2-nitrophenyl pentyl ether as plasticizer and tetrabutylammonium tetraphenylborate as conductivity increaser. An analytically useful potential change occurs in the 1 × 10 −6 to 1 × 10 −1 M concentration range. The slope of linear portion (1 × 10 −4 to 10 −1 M) is 57 ± 1 mV/10-fold concentration changes in iron(III). The measurements were made at constant ionic strength (0.1 M NaNO 3 and 0.1 M HCl) and at room temperature. Here, HCl is used to form FeCl 4 − complex and to protonate the crown ether membrane, since the electrode is sensitive to this anion. In the presence of 1 × 10 −3 M iron(III) no interference was observed for Cl −, NO 3 −, ClO 4 −, SO 4 2−, K +, Na +, Ag +, Cu 2+, Pb 2+, Mn 2+, Cr 3+, Ti 4+ ions. This electrode has been used for the direct determination of iron(III) in blood and in grape molasses which is traditional syrup made of grapes. The amount of iron(III) found was 32 ± 2 μg/100 ml blood and 41 ± 5 μg/g syrup. The lifetime of the electrode was approximately 2 months and the response time was about 30 s.

Mercury(II)-selective polymeric membrane electrode based on the 3-[4-(dimethylamino)phenyl]-5-mercapto-1,5-diphenylpentanone

A new poly(vinylchloride) (PVC) membrane electrode based on 4-(4- N, N-dimethylphenyl)-2,6-diphenylpyrilium tetrafluoroborate as the ionophore was prepared, which shows a good selectivity for mercury(II) ions. The electrode indicates a good linear response for mercury(II) over a wide concentration range from 1.0 × 10 −8 to 1.0 × 10 −3 M, with a near-Nernstian slope of 34 mV per decade and the detection limit is 1.0 × 10 −8 M. This membrane electrode operates well in the pH range of 2.5–7.0 and can be used for at least 30 days without observing any considerable deviation. Selectivity coefficients of some mono-, di- and trivalent metal ions were also determined. The sensor exhibits high selectivity towards mercury(II), compared with the alkali, alkaline earth and transition metal ions. The electrode was also applied as an indicator electrode for potentiometric titration of mercury(II) ion with I −.

A Selective Membrane Electrode for Lanthanum(III) Ion Based on a Hexaaza Macrocycle Derivative as Ionophore

We have developed a highly La(III)-selective PVC membrane electrode based on a hexaaza macrocycle, 8,16-dimethyl-6,14-diphenyl-2,3,4:10,11,12-dipyridine-1,3,5,9,11,13-hexaazacyclohexadeca-3,5,8,11,13,16-hexaene [Bzo2Me2Pyo2(16)-hexaeneN6] (I) as membrane carrier, dibutylbutyl phosphonate (DBBP) as solvent mediator and sodium tetraphenylborate (NaTPB) as lipophilic additive. The best performance was given by the membrane of macrocycle I having a composition 10:260:5:120 (I:DBBP:NaTPB:PVC). The electrode exhibits a Nernstian response to La(III) ion in the concentration range 1.0x10(-1)-7.94x10(-7) M with a slope of 19.8+/-0.2 mV/decade of concentration and a detection limit of 5.62x10(-7) M. The response time of the sensor is 12 s and it can be used over a period of 4 months with good reproducibility. The electrode works well over a pH range of 2.5-10.0 and in partially non-aqueous medium with up to 30% organic content. The sensor was also used as an indicator electrode in potentiometric titration of La(III) ions with EDTA and for determining La(III) concentration in real samples.