Ion-selective Membrane Electrodes Research Articles

Preparation and characterization of CNTs reinforced polyaniline@Zn-CuO nanocomposite for environmental applications

New and novel heavy metal ion selective organic-inorganic composite CNTs reinforced polyaniline@Zn-CuO was expediently obtained by the sol-gel method. Conducting monomer, aniline was polymerized by in situ chemical oxidation. The CNT reinforced polyaniline@Zn-CuO was used for the preparation of ion-selective membrane. The prepared membrane was characterized for porosity, swelling, and find suitable to be used for the preparation of modified ion-selective membrane electrode. The prepared electrode was calibrated with different metal ions and found suitable selective for Hg2+ ions. The electrode showed excellent results as the limit of detection (1 × 10−6 M), working conc range (1 × 10−1 M to 1 × 10−6 M), pH working range (3–6), and response time 17 Sec with room temperature stability two and half month while 30.2 mV is the Nerstian slope obtained by per decade change in metal ion concentration of Hg2+. The practical utility of the proposed membrane sensor assembly was tested by its use as an indicator electrode in the potentiometric titrations.

Evaluation for Plasticization of Ion-selective Electrode Membranes Prepared from Different Solvents Using Proton Spin Relaxation Time

Evaluation for Plasticization of Ion-selective Electrode Membranes Prepared from Different Solvents Using Proton Spin Relaxation Time

Electrochemical Sensors for Biological and Environmental Application

Electrochemical sensors have been developed for last few decades in many different types and ways. They can be applied in various fields of study such as biomedical or biomaterials, environment, and energy, etc. Few projects will be introduced in the conference to show how these sensors can solve such problems. One of the sensors we’ve developed is used to quantify pH and H2O2 simultaneously in real-time to study oral bacterial metabolism in micro-environment. One species of oral bacteria takes glucose and produces H2O2 which plays a key role in maintaining healthy oral condition. We assume that the H2O2 production will increase at higher pH. Since bacterial metabolism and interspecies interaction occurs in few-micron surrounding from bacterial community, it is very challenging to approach there without destroying samples. Thus, we are using few techniques here; Scanning electrochemical microscopy enables us to control and fix the distance between a substrate and an extremely small microelectrode. Another sensor we are working on has unique composition of ion-selective electrode (ISE) membrane. ISE membrane is primarily made of insulating PVC that limits its use as an amperometric electrode. However, our sensor has a carbon-based dual function ISE membrane. It is capable of switching between amperometric and potentiometric measurements without affecting the selectivity coefficients of ISEs. It showed an impressive nM and pM detection limit of Cu2+ and thus opening new avenues of exploiting the excellent selectivity of ISEs and low detection limit of ASWSV techniques. This sensor can be applied to trace heavy metal ions concentration in unknown liquid sample and to determine their solubility depending on pH. The design of sensor and experimental setup will be presented.

Emulsion Doping of Ionophores and Ion-Exchangers into Ion-Selective Electrode Membranes.

Ion-selective electrodes (ISEs) are widely used analytical devices to selectively measure ionic species. Despite significant advances in recent years, ion-selective membranes are still mostly prepared in the same manner, by preloading the selective components into a solvent that is subsequently cast into a membrane or film. This paper describes an alternative method to prepare ISE membranes by mass transfer of the sensing components from an emulsion phase. Specifically, blank (undoped) plasticized poly(vinyl chloride) (PVC) membranes mounted into an electrode body are immersed into an aqueous solution containing analyte ions and an appropriate emulsion of the desired sensing components to allow their transfer into the membrane. The concept is demonstrated with conventional membrane electrodes containing an inner solution as well as all-solid-state electrodes. It is shown to be universally useful for the realization of ISEs for K+, Na+, Ca2+, and NO3-.

Polymeric membrane ion-selective electrodes with anti-biofouling properties by surface modification of silver nanoparticles

Polymeric membrane ion-selective electrodes (ISEs) have been widely applied in environmental analysis. In many cases of practical relevance, however, when these sensors are applied in complex samples, they could suffer from problems of biofouling (related to microorganisms and biofilms) which may shorten the sensors’ lifetimes and cause the measurement errors. Herein, we describe a robust and effective method to endow the ISE membranes with anti-biofouling properties based on surface modification of silver nanoparticles (Ag NPs). The ISE membrane is modified with the hydrophilic polydopamine (PDA) followed by in-situ formation of Ag NPs. The PDA modification enhances anti-adhesive properties of the ISE membrane by increasing the surface hydrophilicity, while Ag NPs impart strong anti-microbial properties to the membrane. A classical polymeric membrane K+-ISE has been chosen as a model. Compared to the unmodified K+-ISE, the Ag NPs modified K+-ISE exhibits significantly improved anti-biofouling properties in terms of the low viability and adhesion rates of bacteria while retaining its original potentiometric ion response properties. Moreover, Ag NPs on the sensor surface show an excellent long-term stability. We believe that the proposed approach can be extended to improve the anti-fouling abilities of other polymeric membrane-based electrochemical sensors for detection in complex environmental samples.

Thin polymeric membrane ion-selective electrodes for trace-level potentiometric detection

In this work, we describe a novel method to improve the detection limits of the non-classical polymeric membrane ion-selective electrodes (ISEs) which are conditioned with highly discriminated ions instead of primary ions. It is based on a thin-layer ISE membrane with a thickness of 5 μm, which is coated on ordered mesoporous carbon used as solid contact. The diffusion of the primary ion from the surface of the sensing membrane to the bulk of the membrane could be avoided by the proposed thin membrane configuration. Since the detection sensitivity of the non-classical ISEs depends on the accumulation of the primary ion in the interfacial layer of the sensing membrane, a lower detection limit can be obtained. By using the copper ion as a model, the present potentiometric sensor shows a significantly improved detection sensitivity compared to the conventional ISE with a membrane thickness of ca. 200 μm. Low detection limits of 0.29 and 0.53 nM can be obtained in 0.01 and 0.5 M NaCl, respectively. In addition, the proposed sensor exhibits an excellent reversibility by using a neutral proton-selective ionophore incorporated in the thin membrane.

Development and characterisation of polyaniline/titanium conducting polymer based ion exchange material for removal of toxic metal ions

ABSTRACT Industrial effluents contain many toxic heavy metal ions and they are the main source for water pollution. Different methods are adopted for the purification of infected water. Among the diverse techniques, ion exchange method using conducting polymer based ion exchange material has several advantages over than other traditional methods like adsorption. In the present work, polyaniline/Ti(IV) iodosulphosalicylate (PANI/Ti(IV) ISS) a conducting polymer based ion exchange material was synthesised by sol–gel method via the mixing of inorganic precipitate of Titanium(IV) iodosulphosalicylate (Ti(IV) ISS) into the matrix of organic conducting polymer polyaniline (PANI). The PANI/Ti(IV) ISS conducting polymer based ion exchange material was well characterised using techniques such as Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction studies (XRD), scanning electron microscopy (SEM), energy dispersive X-Ray (EDAX), transmission electron microscopy (TEM) and thermal (TGA/DTG) analysis. The ion exchange capacity, elution behaviour, elution time and pH titration studies were also investigated. Furthermore a.c. electrical conductivity studies and impedance spectrum of this material also carried out. Some binary separations of heavy metal ions were achieved by the column packed by PANI/Ti(IV) ISS conducting polymer based ion exchange material. PANI/Ti(IV) ISS conducting polymer based ion exchange material showed an ion exchange capacity values (IEC) for Li+, Na+ and K+ which were found to be 1.98, 2.49 and 2.68 meq/g respectively. Based on the distribution coefficient values, PANI/Ti(IV) ISS conducting polymer based ion exchange material was found to be selective for the removal of Pb2+ ion, and the Kd value of 493.02 mL/g for Pb2+ ion from a mixture of toxic metal ions. Pb(II)ion from a synthetic mixture can be removed quantitatively by using PANI/Ti(IV) ISS and it is a promising candidate for ion selective electrode membrane studies.

Developing an Ion-Selective Electrode Membrane Sensor to Detect Lead Levels in Drinking Water

Lead contamination in drinking water is often a close-to-home contamination caused by corroded lead service pipes connecting households to main lines or lead-based pluming within the households. This is particularly evident in houses built prior to 1986 when the United States Environmental Protection Agency (EPA) amended the Safe Drinking Water Act (SDWA) to prohibit the use of any lead-based pipe. Despite the legally established action limit of lead level of 15 parts-per-billion (ppb) in drinking water, incidents with disastrous consequences have occurred repeatedly (e.g. water crisis in Flint, Michigan). The objective of this research is to develop a polymeric ion-selective electrode (ISE) for the detection of lead levels at the EPA action level, or 10-9 molar concentration (M). Primarily, various ratios of sodium tetraphenylborate, resin powder, and lead-selective ionophore were considered and investigated to accomplish this goal. Two commercially available ionophores (Dibenzo-18-Crown-6 and Tert-Butylcalix(4)Arene-Tetrakis) were investigated as well as a synthesized poly (AN-co-HSA) copolyaniline ionophore. The commercially available ionophores were able to consistently achieve a limit of detection (LOD) of 10-6 M when used for the ISE electrode while the synthesized ionophore showed a less consistent LOD between 10-6 M and 10-9 M.

Hydrothermal biosynthesis of chromium sulphide nanoparticles using egg yolk and its catalytic activity in degradation of dyes

Wastewater generated from industries consists of non-fixed dyes contributing to environmental pollution. Use of nanotechnology is being exploited for efficient degradation of dyes. Chromium sulphide nanoparticles have potential biological applications such as ion-selective membrane electrodes and probes for colocalization of membrane proteins. The biosynthesis of chromium sulphide nanoparticles by a high temperature hydrothermal approach has been reported herewith using chromium trioxide as the source of chromium and egg yolk (yellow) as the natural source of sulphur. Catalytic efficiency of chromium sulphide nanoparticles calcinated at 400 °C and 1000 °C has been tested for degradation of congo red, eosin Y, methylene blue as well as bromo cresol green of as prepared solutions and at acidic pH (pH 2.0).

Application of PVC Membrane and Modified Carbon Nanotubes Paste as Electrochemical Sensors for Potentiometric Determination of Loperamide Hydrochloride

Objectives: The main purpose of this work is to design a simple, sensitive, accurate and precise potentiometric membrane ion selective electrodes for selective determination of loperamide hydrochloride in bulk powder and in pharmaceutical preparation. Methods: Electrochemical behavior of loperamide hydrochloride were investigated using PVC membrane and modified carbon nanotubes paste sensors. The linearity of this developed method was established in the concentration range of 10-5 - 10-2 M and10-6 - 10-2 M shows a Nernstian slope of 57.38 mV and 58.74 mV for PVC and Carbon paste sensor, respectively. Results: Validation parameters such as specificity, linearity, accuracy, precision, stability, limit of detection were found to be within the acceptance limit as studied according to IUPAC recommendation data. Conclusion: Both sensors are successfully applied for potentiometric determination of loperamide hydrochloride in its pure form and pharmaceutical formulations.

Developing a potentiometric sunset yellow selective electrode and its applications

We developed a potentiometric ion-selective electrode (ISE) for detecting the food dye sunset yellow (SY). Sunset yellow-Methyltrioctylammonium chloride ion pairs were synthesized. The ion pair that was synthesized was employed as ionophorein the configuration of the electrode membrane. PVC membrane ion-selective electrodes in various compositions were produced using the ion pairs that were synthesized and then, potentiometric performance characteristics of these electrodes were investigated. It was determined that the electrode with the composition of 3.0 % sunset yellow-Methyltrioctylammonium (Sunset-MTOA) ion pair, 64.8 % nitrophenyloctyl ether (NPOE), 32.0 % polyvinylchloride (PVC) and 0.2 % potassium tetrakis (4-chlorophenylborate) (KTpClPB) demonstrated the best potentiometric performance properties. The linear range, slope, limit of quantification, pH range, and the response time of the electrode were determined as 1.0 × 10-5-5.0 × 10-2 M, 23.6 mV,1.0 × 10-5 M,6.4-9.1, and ≈ 5 sec, respectively. The electrode exhibited a highly repeatable potentiometric response

Farmasötik İlaçta İzoprenalin Tayini İçin Potansiyometrik Sensör Geliştirilmesi

In this study, a potentiometric ion-selective electrode (ISE) was developed for the determination of isoprenaline, a pharmaceutical active substance. For this purpose, initially, IP-PM, IP-TCA, IP-TPB, IP-REY, IP-PTA ion pairs were synthesized. The synthesized ion pairs were used as the ionophore in the structure of the electrode membrane. In order to ensure membrane optimization, PVC membrane ion selective electrodes were produced in various compositions using the synthesized ion pair and the potentiometric performance characteristics of these electrodes were investigated. It was determined that the best potentiometric performance characteristics were obtained with the PVC membrane electrode in the composition of 3.0% isoprenaline-tetrafenylborate ion pair, %64.0 nitrophenyloctylether, 32.0% polyvinylchloride and %1.0 Tetrakis (4-chlorophenyl) boron potassium compound. The linear operating range of this electrode is 5.0x 10 -6 M - 1.0x 10 -1 M and the slope at the 10-fold concentration change is 45.3 mV; determination limit, 5.0x10 -6 M, pH working range, 2.6-3.6 and 5.7-7.9; response time < 5s. The electrode exhibited a reproducible potentiometric response. Isoprenaline content was determined in drug by using the isoprenaline selective electrode.

Ion-selective membrane electrode for diclofenac determination

A new membrane ion-selective electrode (ISE) based on the use of the diclofenac-toluidine blue ion associate (IA) as an electrode substance (EAS) is developed. It is shown that the optimal concentration of IA in the PVC membrane is 5 – 11%. The effect of the plasticizer content on the linearity and steepness of the electrode function, as well as on the lower limit of diclofenac ion determination is studied. The best ratio of a plasticizer to PVC is (1.0 – 1.5):1. The content of the plasticizer is obviously related to the electrode lifetime which is mainly determined by the frequency of usage being 7.0 – 7.5 months on the average. The best sensor characteristics were obtained using the following composition: ion associate — 7%, dibutyl phthalate — 56%, PVC — 37%. The electrochemical sensor has a linear dynamic range of 5.0 Ч 10 –4 – 5.0 Ч 10 –2 M, electrode slope of 46.0 mV/pc with a lower detection limit of 3.2 Ч 10 –5 M, and response time <15 sec. The low-cost sensor is easy to use, exhibits fast response, wide range of the electrode function linearity, high selectivity to diclofenac and can be used for at least seven weeks. The new method of diclofenac determination is developed and tested on model solutions and pharmaceuticals.

Implementation of a Chloride‐selective Electrode Into a Closed Bipolar Electrode System with Fluorimetric Readout

AbstractApplicability of a bipolar electrode system was tested for arrangements containing a typical ion‐selective electrode (ISE) connected with an electrode coated by a conducting polymer characterized by electroluminescence. In this case a selective response of the ISE membrane at one pole of the bipolar electrode is transduced to a fluorimetric signal obtained by reduction of the conducting polymer at the second pole. This signal transformation mode was studied on example of a simple closed bipolar electrode system composed of all‐solid‐state chloride‐selective electrode with polypyrrole transducer as the sensing pole and the reporting pole represented by electrode coated by poly(3‐octylthiophene) (POT) layer characterized by fluorescence in the neutral state. In this system selective and linear dependences of fluorimetric signal on logarithm of chloride ions concentration in turn‐on mode were recorded for optimized external voltage applied. Alternatively, a concept of cascade bipolar electrode system with incorporation of additional bipolar electrode being a polarization source for the sensing bipolar electrode with ISE and POT layer was also tested. A significant advantage of the cascade system is its possibility to work spontaneously without external polarization. For this case also linear calibration plots of fluorimetric signal vs. logarithm of analyte concentration were recorded.

Proton spin relaxation study with pulsed NMR on the plasticization of Na+ ion-selective electrode membranes prepared from PVCs with different degrees of polymerization.

The proton spin-spin relaxation times (T2) of ion-selective electrode membranes with differences in the polymerization degree of the incorporated poly(vinyl chloride) (PVC) polymers were investigated. T2 measurements were performed using Hahn-Echo, Solid-Echo and Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences. Analyses of the T2 measurements by Hahn-Echo pulse sequences could realize the estimation of the homogeneity and compatibility for a series of ion-selective electrode membranes and reveal a relationship with the electromotive force (EMF) response in the low-concentration region of the Na+ ions. On the other hand, the normalized derivative spectra from T2 measurements by Solid-Echo and CPMG pulse sequences could approximately visualize the degree of plasticization for such potentiometric polymeric membranes. Moreover, differences in the polymerization degrees of the incorporated PVCs were scarcely found to affect the selectivity coefficients of the Na+-ISEs based on bis(12-crown-4).

Expropriation of Cd(II) from wastewater by ion-selective membrane electrode based on Polypyrrole-Antimony(III)iodophosphate nanocomposite

The objective of the present study was to assess the suitability and efficiency of synthesized Polypyrrole-Antimony(III)iodophosphate (Ppy-SbIP) nanocomposite for the removal of Cd(II) from aqueous solution. Nanocomposite cation exchanger membrane was prepared by solution casting method using Polypyrrole-Antimony(III)iodophosphate and polyvinyl chloride (PVC) as a binder. The synthesis of membrane was confirmed by characterization of the nanocomposite membrane by various instrumentation techniques like SEM, EDX, FTIR, XRD, TGA. The experimental equilibrium data were tested by various potentiometric studies like Calibration curve, Transport no., Effect of pH, Response time, Potentiometric titration studies. The experimental data was best followed by selective for Cd(II) metal, having detection limit (1×10-9 M to 1×10-1 M), response time (20s) and working pH range (3-8). The analytical utility of this electrode was established by employing it as an indicator electrode in potentiometric titration. Various experimental parameter studies proved the absorption of Cd(II) on nanocomposite. Therefore, the present nanocomposite could be applied to purify metal contained wastewater

Photoelectric current as a highly sensitive readout for potentiometric sensors.

We report here a general strategy to read out potentiometric signals via a photoelectrochemical method. The photocurrent at a working electrode coated with a ZnSe/r-GO composite can be modulated by a polymeric membrane ion-selective electrode that works as a reference electrode.

Non-constancy of the bulk resistance of ionophore-based Cd2+-selective electrode: A correlation with the water uptake by the electrode membrane

The dependence of the bulk resistance of Ion-selective electrodes (ISEs) on the concentration of aqueous solution is studied by means of chronopotentiometry and electrochemical impedance using Cd2+-ISE as model system. It is shown that within the Nernstian response range that bulk resistance of the ISE membrane increases along the dilution of the aqueous phase. The results are consistent with analogous studies carried out earlier with Ca2+, K+ and NO3−-ISEs. Water uptake by the Cd2+-ISE membrane is studied systematically, and it is shown that the water uptake also increases along decrease of the concentration of CdCl2 solution. The shapes of the concentration dependence of the two properties: (1) the membrane bulk resistance and (2) the water uptake, are very similar, suggesting a correlation between (1) and (2). SEM/EDX studies of Cd2+-ISE membranes confirm uniform distribution of the components within dry membranes, except of surface layers which are enriched in plasticizer and depleted in the polymer. It is concluded that the ISE membranes equilibrated with aqueous solutions must be considered as non-homogeneous materials due to the presence of the dispersed water. It is assumed that the electrochemical equilibrium is established between the solution and the membrane organic phase proper, while the resistance refers to the membrane as a material including water droplets which hinder the charge transfer across the membranes.

Paradox of the Variation of the Bulk Resistance of Potassium Ion-Selective Electrode Membranes within Nernstian Potentiometric Response Range

Bulk resistance and other electrochemical properties of membranes of K+-selective electrodes (ISEs) containing valinomycin are measured by means of chronopotentiometry and electrochemical impedance. It is shown that the bulk resistance of the membranes, within the Nernstian potentiometric response range, increases along decrease of KCl concentration in solution. Analogous results were reported earlier for Ca2+ and NO$$_{3}^{ - }$$ ISEs. This non-constancy of the bulk resistance is in conflict with current views on the mechanism of ISEs response. Tentatively, this paradox is ascribed to heterogeneity of membranes due to water uptake from solution.

Humanoid Robot Actuation through Precise Chemical Sensing Signals

AbstractAs the need for assistive robots increases in aging societies, various assistive robot systems including humanoid robots have been developed. Humanoid robotic hands are one of the most useful parts to assist humans efficiently. While sensing pressure or temperature from the robotic hands is extensively studied, sensing chemicals is less widely studied despite the significant importance. Here, a unique platform of smartly moving humanoid fingers actuated by chemical sensing is reported. The sensor is printed with disposable and biocompatible cellulose conductive ink materials. Rf intensity change of the sensor with NH4+ membrane depends on NH4+ ion concentration where R² is 0.9576. The smart bending motion of a finger is accomplished by logically programed actuation through detecting the change of interested ion concentration from 0.01 to 1 m at the ion‐selective membrane electrode (ISME) sensor with resulted bending angles from 10° to 67° accordingly. The overall signal‐to‐noise ratio is over 10. This sensing robot concept may be expanded to applications of microrobots which receive external stimulus, judge, and execute the actuation to carry out programed tasks.