Coulometric Response of H+-Selective Solid-Contact Ion-Selective Electrodes and Its Application in Flexible Sensors†

The analytical performance of H⁺-selective solid-contact ion-selective electrodes (SCISEs) based on solid contact polyaniline doped with chloride (PANI(Cl)) and poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT(PSS)) was characterized by a developed coulometric signal transduction method. PEDOT(PSS) solid contact is covered by PVC based H⁺-selective membrane. The obtained coulometric signal demonstrates that the cumulated charge can be amplified by increasing the capacitance of solid contact. SCISEs covered with spin-coated membrane behave faster amperometric response than electrodes with drop-cast membrane. In contrast to earlier works, the amperometric response and impedance spectrum demonstrates H⁺ transfer through SCISEs is independent from the thickness of membrane. The exceptional behavior of PANI(Cl) H⁺-SCISEs shows that the capacitance estimated from impedance spectrum at low frequency 10 mHz and coulometric signal of PANI(Cl) based SCISEs is influenced by the applied potentials, whereas PEDOT(PSS) solid contact is independent from the chosen applied potentials. Furthermore, preliminary investigations of coulometric signal transduction on flexible pH sensor implies its potential applications in wearable sensors for sweat ion concentration detection.      

Ion-Selective Electrodes Prepared with Polyaniline Membranes

Polyaniline is a conductive polymer that has electrochemical activity. For this reason, it has many different uses in electrochemical area. In this study, polyaniline was prepared by electrochemical oxidation of aniline in concentrated H₂SO₄ and HCl solutions. Then, membranes were obtained from a mixture of these polymers and paraffin at a weight ratio of 50%. Ion-selective electrodes were prepared with these membranes and AgCl/Ag electrodes. Properties of prepared membranes were investigated with potentiometric measurements made in HCl, KCl, H₂SO₄, and HClO₄ solutions of different concentrations. The E–logc plots obtained with these ion-selective electrodes were found to be linear in a distinct concentration range. Their slopes depend on the membrane type and the doping ion in the test solution. The difference between these membranes was explained according to the morphological structures of polyaniline membranes.     

Arginine Determination with Ion-Selective Membrane Electrodes

Abstract

A new method for the determination of the amino acid arginine utilizes a dual enzyme catalyzed reaction monitored with an ammonium ion selective membrane electrode of the antibiotic type. The technique gives a linear correlation between arginine concentration and electrode response over the 3 × 10^?3 M to 3 × 10^?5 M range and a useful, but non-linear, response over a wider range. Major interferences are urea, K⁺, and NH₄ ⁺, but Na⁺ does not interfere in the physiological concentration range.     

Determination of Antiseptic Dyes with Ion-Selective Electrodes

The possibility of determining Methylene Blue and Brilliant Green antiseptic dyes in solutions with the use of ion-selective electrodes based on trioctyl oxybenzosulfonic acid was examined. Data on application of the electrodes fabricated to analysis of powdered dyes are presented. A gravimetric method for analysis for Brilliant Green was suggested and used as a comparative technique.     

Complex Formation Studies with Cupric Ion-Selective Membrane Electrodes

Abstract

A cupric ion-selective electrode of the liquid-liquid membrane type is shown to respond selectively to Cu⁺⁺ activity over the range of pCu⁺⁺ = 2–5 in aqueous solutions of pH 3.5–6.5. Cupric ion activity measurements in the presence of complexing ligands have yielded a reliable estimate of formation constants for a number of soluble copper complexes.     

Determination of Some Thiobarbiturates with Ion-Selective Membrane Electrodes

Abstract

A liquid membrane Ag⁺-selective electrode of our construction and a commercial solid membrane Ag⁺/S^2--selective electrode were used for the determination of thiobarbiturates by potentiometrie titration with AgNO₃ solution or by direct potentlometry. The potentio-setrio data correlated vd. th IR spectra allowed the elucidation of the reaction mechanism.     

Separate Determination of Homologous Sodium Alkyl Sulfates with Ion-Selective Electrodes

The possibility of the separate determination of homologous sodium alkyl sulfates with ion-selective electrodes and using multisensor analysis was studied. The optimum component ratios were found for the analysis of model mixtures with ion-selective electrodes. It was shown that nonlinear regression analysis and artificial neural networks can be used for processing analytical signals from a set of weakly selective sensors for anionic surfactants.     

Ion-Selective Electrodes for the Determination of Nitrogen-Containing Medicinal Substances

Stoichiometric ratios and solubility products were determined for medicinal substance–tetraphenyl borate ion pairs. The influence of the nature of the medicinal substance cation incorporated into ionophores and the effect of the solvent–plasticizer on analytical characteristics were studied. The optimal composition of membranes was determined. Ion selective electrodes were used for the potentiometric determination of dimedrol, papaverine, novocaine, and lidocaine in medicinal forms.     

Determination of β-Lactam Antibiotics by Potentiometry with Ion-Selective Electrodes

Ion-selective electrodes for antibiotics from the penicillin series, with membranes based on three different classes of ionophores (anion exchangers, aza compounds, and metal phthalocyanines), were proposed. The electrochemical and performance characteristics of the sensors were studied and compared.     

Determination of Inorganic and Organic Thiophosphates with Ion-Selective Membrane Electrodes

Abstract

The conditions for the determination of sodium thiophosphate and sodium S-(2-amino-ethyl)-thiophos-phate in the presence of phosphate ion using ion-selective membrane electrodes are described. Both thiophosphates (inorganic and organic) are hydrolyzed in acidic medium. The phosphate ion is determined with Pb(II) using a Pb²⁺ – selective membrane electrode.

Cysteamine is determined by potentiometric titration with Hg(I1) using a Ag⁺/S^2? – crystal membrane electrode or by direct potentiometry with a Cu²⁺ selective membrane electrode. The results were verified by the iodination method.     

用交流阻抗法研究某些离子选择电极的响应特性

用交流阻抗法研究了两种液膜胆R汁酸电极和两种聚氯乙烯(PVC)膜钙离子选择电极. 从体电阻R_b和电荷传递电阻R_(ct)得到膜内离子迁移活化能E_a, 及电极的表观标准交换电流密度i°_0等信息. 结果表明: E_a比R_b更能反映离子在膜内迁移的情况, 离子在PVC膜中的迁移比在液膜中困难得多; i°_0能在一定程度上反映电极性能的优劣等。     

Preparation of Thallium Hexacyanoferrate Film and Mixed‐Film Modified Electrodes with Cobalt(II) Hexacyanoferrate

Thallium hexacyanoferrate films have been prepared from various aqueous electrolyte solutions using consecutive cyclic voltammetry. The cyclic voltammograms recorded the direct deposition of thallium hexacyanoferrate films from the mixing of Tl³⁺ and [Fe(CN)₆]^3? ions from solutions of seven cations: Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, H⁺, and Tl⁺. An electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the thallium hexacyanoferrate films. The thallium hexacyanoferrate film shows a single redox couple with a formal potential between +0.6 V and +1.2 V, and shows a cation effect (H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and Tl⁺). A mixed film and a two‐layered modified electrodes composed of a thallium hexacyanoferrate film with cobalt(II) hexacyanoferrate film were prepared.     

用于高性能铅离子选择电极的含氮有机物载体

本文系统地综述高性能铅离子选择电极中掺杂于膜内的含氮有机物铅离子传感载体,如双席夫碱、吡啶酰胺、酰羟胺、苯腙,以及载体分子结构特征与铅离子电极性能之间的关系。电极对铅离子的选择性能与载体分子结构密切相关,无论是在载体还是在膜基体中引入氰基都可以明显改善铅离子电极探测下限;加强传感机理的深入研究,为高性能载体的研究指明方向。     

Determination of Nitrilotriacetic Acid (NTA) with Ion-Selective Membrane Electrodes

Abstract

A solid membrane copper ion selective electrode was used for the determination of NTA via complexometric titration with copper(II). Interferences, of the type commonly found in detergents, were investigated.     

A new Chloride-Selective Carrier and its Evaluation in Ion-Selective Electrodes

 A new chloride selective carrier, the tributyltin cinnamate, is evaluated for its analytical characteristics when incorporated in liquid polymeric membranes of ion-selective electrodes. The electrode constructed based on this carrier exhibited an improved selectivity towards chloride as compared to those based on the existing chloride carriers, completely satisfying the selectivity for direct blood measurements. Additionally, the response time of the sensor is fast, while the good signal stability allows for the application as a stand-alone device or as a detector in FIA system. The electrode exhibited analytical characteristics suitable for its employment in a variety of real-sample analysis.     

Nitrogen-Bearing Organic Compounds as Carriers for Lead Ion-Selective Electrodes with Excellent Response

Bis-Schiff base, pyridyl carboxamide, acylhydroxylamine, and phenylhydrazone, acting as sensing agents in ionophore-doped membranes of lead-ion selective electrodes with excellent response characteristics, are systematically summarized according to the latest literatures and our latest researches. The relationship between the response characteristics of the lead (II) ion-selective electrode assembled by the carriers and their molecular structures is also elaborated. It is noteworthy that the selectivity of the electrode towards lead ions over other cations is closely related to the molecular structure of the carrier. The presence of cyano group would largely improve the lower detection limit whether it is introduced into the carrier or membrane matrix. The sensing mechanism should be emphasized in order to find out the direction for developing high performance carriers.     

New Ion-Selective Electrodes for Determination of Bupivacaine and Oxybuprocaine

Abstract

PVC membrane electrodes selective for hydrochlorides of the anaesthetics bupivacaine (BpC) and oxybuprocaine (ObC) are prepared. The electrodes have a near Nernstian slope (58 mV for BpC and 51 mV for ObC electrodes) over the range of 1.6 × 10^?5-10^?1M and 1.3 × 10^?1M for BpC and ObC electrodes, respectively. The change in pH of the test solution within the ranges 2.5–6.0 and 3.0–7.4 does not affect the EpC-and ObC-electrodes, respectively. The electrodes have very long life times (10 days for BpC, and 3 months for ObC) and exhibit good seletivity for the investigated compounds with respect to a large number of inorganic cations and organic substances of biological importance. The isothermal coefficients of the electrodes are calculated from the standard electrode potentials at different temperatures. BpC and ObC are determined successfully in some pharmaceutical preparations using the calibration graph technique and potentiometric titration.     

A Comparative Study between Screen-Printed and Solid-Contact Electrodes for the Stability-Indicating Determination of Bromazepam

Stability-indicating methods are awesome tools to ensure the safety and efficacy of active pharmaceutical ingredients (APIs). An accurate comparative study involving the use of potentiometric sensors for the determination of bromazepam (BRZ) in the presence of its main product of degradation and impurity was performed by the fabrication of two membrane electrodes. A screen-printed electrode (SPE) and a solid-contact glassy carbon electrode (SCE) were fabricated and their performance optimized. The fabricated sensors showed a linear electrochemical response in the concentration range 1.0 × 10⁻⁶ M to 1.0 × 10⁻² M. The electrodes exhibited Nernstian slopes of 59.70 mV/decade and 58.10 mV/decade for the BRZ-SPE and BRZ-SCE membrane electrodes, respectively. The electrochemical performance was greatly affected by the medium pH. They showed an almost ideal electrochemical performance between pH 3.0 and pH 6.0. The fabricated membranes were applied successfully for the quantification of BRZ in the presence of up to 90% of its degradation product. Moreover, a successful application of the fabricated electrodes was performed for the sensitive and selective quantification of BRZ in its tablet form without any pretreatment procedure.     

Perchlorate Ion-Selective Electrodes with the Liquid Membranes of the O-Phenanthroline Chelate or its Related Compounds

Abstract

The metal chelates of o-phenanthroline, a, a′-dipyridyl or bathophenanthroline were used as the ion exchanger in the liquid membrane of the perchlorate ion-selective electrode. The electrode with a nitrobenzene membrane containing tris(bathophenanthroline)ferrous perchlorate is the highest sensitive one and gives a linear Nernstian response up to about 1 × 10 ^?5 M perchlorate. The membrane electrode having the ferrous ion-chelate of o-phenanthroline as an ion exchanger shows an excellent selectivity for perchlorate ion over nitrate or iodide Ion. The effects of the chelate concentration in the membrane and the central metal species of the chelate are examined on the electrode performance.