Potentiometric Response Research Articles

Analytical Tool for Quality Control of Irrigation Waters via a Potentiometric Electronic Tongue

A potentiometric electronic tongue (ET) for the analysis of well and ditch irrigation water samples is herein proposed. The sensors’ array is composed of six ion-selective electrodes based on plasticized polymeric membranes with low selectivity profiles, i.e., the membranes do not contain any selective receptor. The sensors differ between them in the type of ion-exchanger (sensors for cations or anions) and the plasticizer used in the membrane composition, while the polymeric matrix and the preparation protocol were maintained. The potentiometric response of each sensor towards the main cations (Na+, K+, Ca2+, Mg2+) and anions (HCO3−, Cl−, SO42−, NO3−) expected in irrigation water samples was characterized, revealing a fast response time (<50 s). A total of 19 samples were analyzed with the sensor array at optimized experimental conditions, but, also, a series of complementary analytical techniques were applied to obtain the exact ion composition and conductivity to develop a trustable ET. The principal component analysis of the final potential values of the dynamic response observed with each sensor in the array allows for the differentiation between most of the samples in terms of quality. Furthermore, the ET was treated with a linear multivariate regression method for the quantitative determination of the mentioned ions in the irrigation water samples, revealing rather good prediction of Mg2+, Na+, and Cl− concentrations and acceptable results for the rest of ions. Overall, the ET is a promising analytical tool for irrigation water quality, exceeding traditional characterization approaches (conductivity, salinity, pH, cations, anions, etc.) in terms of overhead costs, versatility, simplicity, and total time for data provision.

Understanding the potentiometric response of cation-permselective hydrophilic nanopore-based electrodes in the low ion concentration range

Permselective membranes are at the core of important applications and devices, that include ion-selective electrodes, energy conversion, and separation. Here we report the potential response in the low ion concentration range of hydrophilic cation-permselective gold nanopore-based membranes obtained by surface modification with a sulfonate-bearing thiol derivative. Apart from conventional polymeric permselective membranes, we confirmed ‘equal’ potentiometric responses for the same valency cations, that include both inorganic and organic cations. A refined Nernst–Planck/Poisson (NPP) model to account for previously neglected mass transport effects in the low ion concentration domain was shown to accurately predict even the interesting zero current fluxes generated super-Nernstian responses for higher valency cations. For all investigated ions we found that their interaction with sulfonate-groups functionalized nanopores is dominantly electrostatic in its nature. Hence, the synthetic versatility of such permselective nanopores in conjunction with the possibility of a rational design of its properties based on the NPP model renders such nanopore-based membranes not only a convenient alternative to existent permselective membranes, but their unique properties show promises for novel ion-sensing and separation applications.

Dinuclear Pb(II) monomer complex: Synthesis, characterization, and application of Pb(II) ion-imprinted polymer as a selective potentiometric microsensor

A Pb(II) centered [Pb2(maa)4(vim)2] complex was synthesized using methacrylic acid (maaH) and 1-vinylimidazole (vim) containing vinylic groups suitable for polymerization. The structure of the Pb(II) monomer complex was elucidated by single-crystal X-ray diffraction method, fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). A new Pb(II) ion-imprinted polymer (Pb(II)-IIP) was prepared with [Pb2(maa)4(vim)2] complex as functional monomer, ethylene glycol dimethacrylate (EGDMA) as crosslinker and 2,2′-azobisisobutyronitrile (AIBN) as initiator, to use in a Pb2+ selective sensor design. The prepared Pb(II)-IIP was characterized by FT-IR, TGA, energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). Pb(II)-IIP was used as an ionophore in the structure of polyvinylchloride (PVC) membrane of the all-solid-state ion-selective microsensor to obtain a selective potentiometric response for Pb2+ ions. The Pb2+-selective microsensor exhibited a highly selective Nernstian response over a wide linear concentration range of 10−6 to 10−2 mol.L−1 with a slope of 29.4 mV per decade (R2 = 0.9987) in the pH range of 3.0 to 7.0. The response time of the microsensor was very short (less than 15 s) and the detection limit was determined as 8.30 × 10−8 mol.L−1. The lifetime of the microsensor was calculated as 45 days.

Voltammetric determination of phosphates using ion-selective electrode based on organotin ionophore

This work describes the development of an amperometric phosphate-selective electrode with a plasticized membrane that includes bis(2-ethylhexyl)tin (IV) dichloride as an ionophore. The potentiometric response of the plasticized membrane was investigated, in addition to its selectivity for hydrophilic anions. The membrane provided a linear potential response with respect to HPO42- ions in the concentration range from 4·10-5 to 3·10-2 mol/L with a Nernst slope of 29 ± 2 mV·decade-1 activity. By using cyclic voltammetry, we characterized the ionophore-facilitated transfer of mono- and dihydro phosphate ions at the water/PVC-2-nitrophenyl octyl ether phase interface. An interphase distribution coefficient, a galvanic potential, a half-wave potential, the Gibbs energy of facilitated interphase transfer, as well as the Gibbs energy of facilitated interphase transfer were determined. Alternating current voltammetry was used to quantify phosphate ions in aqueous solutions. The linear response was observed in the range of phosphate concentrations from 2 to 10-6 to 1·10-4 mol/L and the detection limit was 8·10-7 mol/L under these conditions. This AISE has demonstrated high selectivity for phosphate ions in comparison to the most common anions in aqueous solutions. It has been used to determine the amount of phosphates in two fertilizers.

Fabrication of an Enzyme Membrane for Creatinine Detection and Its Application to an Extended-Gate FET-Based Biosensor

An extended-gate field effect transistor (EGFET) based creatinine sensor using an enzyme-containing silk-fibroin membrane successfully fabricated. In this experiment, we used creatinine deiminase as a detection enzyme for serum creatinine, which is known as a marker of chronic kidney disease. The fabricated biosensor showed excellent potentiometric response to creatinine over a wide range from 0.007 - 0.4 mg/mL in phosphate buffer solution, which can enable to measure creatinine concentration in blood plasma.

Directly Using Ti3C2Tx MXene for a Solid-Contact Potentiometric pH Sensor toward Wearable Sweat pH Monitoring.

The level of hydrogen ions in sweat is one of the most important physiological indexes for the health state of the human body. As a type of two-dimensional (2D) material, MXene has the advantages of superior electrical conductivity, a large surface area, and rich functional groups on the surface. Herein, we report a type of Ti3C2Tx-based potentiometric pH sensor for wearable sweat pH analysis. The Ti3C2Tx was prepared by two etching methods, including a mild LiF/HCl mixture and HF solution, which was directly used as the pH-sensitive materials. Both etched Ti3C2Tx showed a typical lamellar structure and exhibited enhanced potentiometric pH responses compared with a pristine precursor of Ti3AlC2. The HF-Ti3C2Tx disclosed the sensitivities of -43.51 ± 0.53 mV pH-1 (pH 1-11) and -42.73 ± 0.61 mV pH-1 (pH 11-1). A series of electrochemical tests demonstrated that HF-Ti3C2Tx exhibited better analytical performances, including sensitivity, selectivity, and reversibility, owing to deep etching. The HF-Ti3C2Tx was thus further fabricated as a flexible potentiometric pH sensor by virtue of its 2D characteristic. Upon integrating with a solid-contact Ag/AgCl reference electrode, the flexible sensor realized real-time monitoring of pH level in human sweat. The result disclosed a relatively stable pH value of ~6.5 after perspiration, which was consistent with the ex situ sweat pH test. This work offers a type of MXene-based potentiometric pH sensor for wearable sweat pH monitoring.

Development of Solid-Contact Potentiometric Sensor Utilized Nanocarbon-filled Poly (vinyl chloride) Membrane as Ion-to-electron Transducing Layer

Current fundamental researches in the field of potentiometry demonstrate the perspectives of using polymeric nanostructured materials as ion-to-electron transducers in Solid-Contact Potentiometric Sensors (SCSs). This paper reports the preparation and comparative study of plasticized Poly(Vinyl Chloride) (PVC) membranes modified with fullerene C60, single-walled carbon nanotubes SWCNTs, multiwalled carbon nanotubes, and graphene oxide as the transducing layer in SCSs for the determination of a common local anesthetic drug – procaine hydrochloride (Pro·HCl). As an ion-sensitive (recognizing) layer, a PVC membrane containing highly lipophilic 2-[bis-octadecyl sulfo]-closo-decaborate anions was chosen. The results were discussed in relation to nanofiller’s type and content. The best potentiometric characteristics were obtained for the sensor with the transducing layer containing the hybrid nanofiller SWCNTs/C60. This new sensor of a double-layer PVC membrane configuration exhibited a Nernstian slope (59.2 ± 0.2 mV/decade) in the wide linear range (5×10-7– 1×10-2 M) with the low limit of detection (10-7.1 M), fast response time (≤ 7 s), and stable potentiometric response (drift potential ± 0.27 mV h-1 over 7 h of soaking in 1x10-5 M Pro·HCl solution).

Applicability of a synthesized melamine based covalent organic framework as a novel ionophore for the potentiometric determination of mercury (II): Computational and experimental studies

In this research, the complexation of a recently synthesized covalent organic framework (schiff base network1) with 10 different cations was investigated by QTAIM (quantum theory of atoms in molecules) computations. The theoretical results showed the schiff base network1 interactions with Hg2+ is considerably stronger than other cations and it can be used as an selective ionophore for the development of a potentiometric sensor to determination of Hg2+. Therefore, a Hg2+ selective PVC membrane coated graphite electrode was developed based on schiff base network1. The best response was observed form the membrane composition of PVC (32 %), Nitrobenzene (60 %), sodium tetraphenylborate (2 %), and schiff base network1 (6 %). The designed sensor showed an excellent Nernstian response to Mercury (II) (29.8 mV. Decade−1) over a wide activity range from 1 × 10−7 to 5 × 10−3 and the detection limit of the proposed potentiometric sensor was 8 × 10−8. The effect of different interfering species on the potentiometric response of the suggested electrode was scrutinized by matched potential method (MPM) and no interference was observed. The performance of the developed electrode in partially non-aqueous mediums was also checked out and the obtained results showed the electrode can also be utilized in systems containing %20 organic solvents (ethanol and acetone). The response time and lifespan of the electrode were <10 S and 16 weeks respectively. In the end, the analytical performance of the fabricated sensor for the determination of Hg (II) in three different effluent samples was scrutinized and the obtained results were compared with a standard spectrophotometric technique.

Paper-Based Sandwich-Structured Wearable Sensor with Sebum Filtering for Continuous Detection of Sweat pH.

Wearable sweat sensors, a product of the development of flexible electronics and microfluidic technologies, can continuously and noninvasively monitor abundant biomarkers in human sweat; however, sweat interferences, such as sebum, can reduce sensor reliability and accuracy. Herein, for the first time, the influence of sebum on the potentiometric response of an all-solid-state pH sensor was studied, and the obtained experimental results show that sebum mixed in sweat can decrease the potential response of the sensor and the slope of its calibration curve. A paper-based sandwich-structured pH sensor that can filter the sebum mixed in sweat was proposed based on commonly used oil-control sheets. Moreover, the hydrophilic properties, microstructure, and microfluidic performance of the sensor were investigated. The detection performance of the paper-based sandwich-structured pH sensor was comprehensively evaluated in terms of calibration in the presence of sebum and potentiometric response upon the addition of sebum. Furthermore, the anti-interference ability of the sensor was evaluated using different analytes under various deformation conditions. On-body trials were conducted to verify the performance, and their results showed that the proposed sensor can filter over 90% of the sebum in sweat, significantly enhancing sensor reliability and accuracy. Additionally, microfluidic channels could be simply fabricated using a scissor and paper, obviating the need for complex micromachining processes, such as photolithography and laser engraving. Overall, this work illustrates the influence of sebum on the detection performance of traditional potentiometric wearable sensors and paves the way for their development for real-world applications.

Ion-Selective Membrane Electrode for Determination of the Octahydrotriborate Anion

An ion-selective electrode (ISE) based on a plasticized polyvinyl chloride membrane chemically doped with tetradecylammonium octahydrotriborate ([(С10H21)4N+]) has been developed. It is shown that the electrode has a reversible potentiometric response with respect to the octahydrotriborate anion in the presence of a number of other inorganic anions. The influence of the concentration of the electrode-active material and the nature of the plasticizer in the membrane phase on the electrochemical characteristics of the fabricated sensor have been studied. The optimal composition of the ion-sensitive membrane has been found. It has been found that the developed sensor provides a wide range of detectable concentrations of(1 × 10–7…1 × 10–2) and a low detection limit (10–7.3 M). The new ISE can be recommended for direct potentiometric detection of free octahydrotriborate anions in technological aqueous solutions.

The New Reliable pH Sensor Based on Hydrous Iridium Dioxide and Its Composites.

The new reliable sensor for pH determination was designed with the use of hydrous iridium dioxide and its composites. Three different hIrO2-based materials were prepared and applied as solid-contact layers in pH-selective electrodes with polymeric membrane. The material choice included standalone hydrous iridium oxide; composite material of hydrous iridium oxide, carbon nanotubes, and triple composite material composed of hydrous iridium oxide; carbon nanotubes; and poly(3-octylthiophene-2,5-diyl). The paper depicts that the addition of functional material to standalone metal oxide is beneficial for the performance of solid-state ion-selective electrodes and presents the universal approach to designing this type of sensors. Each component contributed differently to the sensors' performance-the addition of carbon nanotubes increased the electrical capacitance of sensor (up to 400 µF) while the addition of conducting polymer allowed it to increase the contact angle of material changing its wetting properties and enhancing the stability of potentiometric response. Hydrous iridium oxide contacted electrodes exhibit linear response in wide linear range of pH (2-11) and stable potentiometric response (the lowest potential drift of 0.036 mV/h is attributed to the electrode with triple composite material).

Development of a potentiometric sensor for the determination of carbamazepine and its application in pharmaceutical formulations

AbstractBACKGROUNDEpilepsy is a neurological disorder and its treatment is carried out with anti–epileptic drugs. Carbamazepine has been in use since 1965, as a safe and effective anti–epileptic agent. In this paper, a poly(vinyl chloride) (PVC) membrane carbamazepine selective potentiometric sensor was developed for the determination of carbamazepine in pharmaceutical formulations. Carbamazepine–tetraphenylborate (CBZ–TPB) ion−pair was synthesized as an electroactive component and PVC membrane sensors were prepared with different CBZ–TPB ratios. The membrane with the best analytical properties was determined as the one with 2.0% CBZ–TPB ion–pair, 33.0% PVC and 65.0% o–nitrophenyl octyl ether (o–NPOE).RESULTSThe proposed sensor exhibited linear responses over the concentration range 1.0 × 10−5 – 1.0 × 10−2 mol L−1 (R2 = 0.999). The limit of detection was 9.60 × 10−6 mol L−1. The developed sensor showed high selectivity against carbamazepine over some ionic species investigated and also over other anti–epileptic drugs. The potentiometric response of the sensor was not affected by pH in the wide pH range of 4.0–9.0 and the response was fast, at ≈10s.CONCLUSIONThe fabricated carbamazepine–selective sensor was applied for the determination of carbamazepine contents of some pharmaceutical formulations. The potentiometric measurement results for the pharmaceutical formulations gave results with good agreement with data obtained using UV–visible spectroscopy. As a result, the developed carbamazepine selective potentiometric sensor can be considered as an alternative to other analytical methods for the determination of carbamazepine in pharmaceutical samples. © 2022 Society of Chemical Industry (SCI).

Deep Learning‐Enhanced Potentiometric Aptasensing with Magneto‐Controlled Sensors

AbstractBioelectronic sensors that report charge changes of a biomolecule upon target binding enable direct and sensitive analyte detection but remain a major challenge for potentiometric measurement, mainly due to Debye Length limitations and the need for molecular‐level platforms. Here, we report on a magneto‐controlled potentiometric method to directly and sensitively measure the target‐binding induced charge change of DNA aptamers assembled on magnetic beads using a polymeric membrane potentiometric ion sensor. The potentiometric responses of the negatively charged aptamer, serving as a receptor and reporter, were dynamically controlled and modulated by applying a magnetic field. Based on a potentiometric array, this non‐equilibrium measurement technique combined with deep learning algorithms allows for rapidly and reliably classifying and quantifying diverse small molecules using antibiotics as models. This potentiometric strategy opens new modalities for sensing applications.

Deep Learning-Enhanced Potentiometric Aptasensing with Magneto-Controlled Sensors.

Bioelectronic sensors that report charge changes of a biomolecule upon target binding enable direct and sensitive analyte detection but remain a major challenge for potentiometric measurement, mainly due to Debye Length limitations and the need for molecular-level platforms. Here, we report on a magneto-controlled potentiometric method to directly and sensitively measure the target-binding induced charge change of DNA aptamers assembled on magnetic beads using a polymeric membrane potentiometric ion sensor. The potentiometric responses of the negatively charged aptamer, serving as a receptor and reporter, were dynamically controlled and modulated by applying a magnetic field. Based on a potentiometric array, this non-equilibrium measurement technique combined with deep learning algorithms allows for rapidly and reliably classifying and quantifying diverse small molecules using antibiotics as models. This potentiometric strategy opens new modalities for sensing applications.

Erdosteine-based potentiometric sensor for real-time surveillance of copper traces in food supplements and shredded canned tuna

Industrial anthropogenic activities pollute water and contaminate fish with heavy metals. The study presented a chemically modified carbon paste sensor for Cu (II) ion assay based on Cu-erdosteine association complex. The electrode exhibited a Nernstian response (29.6 ± 0.018 mV/decade) with a wide linear concentration range (1.99 ×10−6 −1 ×10−2 mol L−1). Over the pH range of 4.0–6.0, the potentiometric response of the fabricated electrode is independent of pH. The sensor determined the Cu (II) content in drug substances, pharmaceutical formulations, and tuna meat via potentiometric titration with EDTA. The method did not differ statistically from the method described in the literature.

Screen-printed sensors for efficient potentiometric analysis of tolperisone hydrochloride in presence of its co-formulated drugs

Researchers seeking for green chemistry to help safeguard and boost the economy and the environment by discovering unique ways to decrease waste and find substitutes for dangerous chemicals. In this study, a green potentiometric ion-selective electrode (ISE) was developed for measurement of tolperisone HCl (TOLP) in bulk and Pharmaceutical dosage forms in presence of diclofenac sodium and paracetamol as co-formulated drugs. This paper presents the manufacture and characterization of a disposable potentiometric ion-selective strip with an enhanced detection limit for (TOLP) measurement in its tablet dosage form either alone or in presence of the co-formulated drugs. Numerous ion pairs (IPs), such as TOLP-tetraphenylborate (TOLP-TPB), TOLP-phosphotungstic acid (TOLP-PTA), and TOLP-ammonium Reinecke (TOLP- RKT) are tested in presence of different plasticizers. The optimal potentiometric response with a near Nernstian slope of 55.949 mV/decade was achieved within a linear concentration range of 5 times 10–5 − 1 times 10–2 M using (PTA) and ortho nitrophenyl octyl ether (o-NPOE) as a plasticizer. The effect of the nanoparticles on the membrane stability was studied using the graphene nanoplatelets which have an effective role in the enhancement of some constructed sensors stability. Finally, the developed technique is validated for the estimation of TOLP with high accuracy and precision.Graphical

Fast and reliable infection diagnosis during orthopaedic surgery using Bluetooth-assisted miniaturized-electrochemical sensor

Infections are a relevant problem in the orthopaedic field because the risk of infection is universal for all implanted orthopaedic devices. Herein, we reported the design, development, and test of a miniaturized, cost-effective, and Bluetooth-assisted device for fast and easy monitoring of infections during orthopaedic surgery. The new portable miniaturized electrochemical sensor was fabricated using polyester as support and conductive inks for screen printing. The electrochemical sensor was then modified with biocompatible iridium oxide by electrochemical deposition. The pH value of blood was measured by adding a drop of blood, sampled during orthopaedic surgery, onto the electrochemical cell without any sample treatment to obtain a potentiometric response in less than 1 min. The pH value was found lower than 7.0 in the case of infections and the data obtained are in agreement with microbiological analyses, furnishing an accurate diagnosis of infection and paving the way for using the electrochemical sensors in the orthopaedic field as intelligent tools for fast diagnosis.

Dense BaCe0.6Zr0.3Y0.1O3-Α Solid-State Electrolyte for Application in Hydrogen Sensors

Fusion energy is a promising solution for the expected energy problems in the mid-term future. This technology is expected to use deuterium and tritium, two hydrogen isotopes, as fuel. Deuterium can be obtained from natural sources, but tritium, which is a non-stable hydrogen isotope, must be in situ generated. To assure the correct monitoring of both isotopes, it will be required the design and qualification of high-temperature sensors. The construction of H2 sensors based on solid-state electrolytes can be the first step towards the development of new analytical tools able to monitor hydrogen isotopes in that aggressive environment.In previous work [1], amperometric sensors based on BaCe0.6Zr0.3Y0.1O3-α (BCZY) solid-state electrolyte have shown good analytical parameters for hydrogen monitoring. However, these materials need high temperatures during sintering to obtain full density due to their refractory nature. This lack of densification can affect their electrochemical response due to their low ionic conductivity. The use of sintering aids, like ZnO, can improve the densification of these ceramics at lower temperatures.In the present work, hydrogen sensors based on BCZY were constructed and evaluated in potentiometric mode. Different sintering conditions for this electrolyte were tested and their potentiometric response was compared. The following disk-shaped electrolytes were prepared for that purpose: 1400 ºC – 30 h, 1650 ºC – 6h. Simultaneously, BCZY was sintered at 1400 ºC -12 h with 5 mol% of ZnO as a sintering aid. Samples were characterized using XRD (to determine the crystallographic phases) and SEM (for microstructural defects and sintering). Then, disks were platinized and sealed with a glass binder to alumina tubes for sensor construction. Measurements were performed at 400 and 500 ºC. The hydrogen concentration in the RE was 1000 ppm H2 in Ar. The response obtained with the three sensors was compared with the theoretical Nernst potential.[1] A. Hinojo, I. Soriano, J. Abellà, S. Colominas, Evaluation of High-Temperature Hydrogen Sensors Based on BaCe0.6Zr0.3Y0.1O3-α and Sr(Ce0.9Zr0.1)0.95Yb0.05O3-α Perovskites for Industrial Applications, Sensors. 20 (2020) 7258. https://doi.org/10.3390/s20247258.

Novel design of a planar flow-through potentiometric sensor

A novel planar electrode for flow-through potentiometric sensing is presented in this work. Planar and concentric potassium solid-contact ion-selective electrodes (K+-SCISEs) were designed and studied using potentiometry and electrochemical impedance spectroscopy (EIS). The K+-SCISE consisted of a neutral carrier PVC-based ion-selective membrane with valinomycin as ionophore, carbon cloth as ion-to-electron transducer, and a gold wire as electronic conductor, all incased in a polycarbonate support. The prepared electrodes showed a stable and reproducible potentiometric response. The average slopes for three identical flow-through K+-SCISEs, calibrated once per day during five days (n = 15), was 57.2 mV/decade (SD = 0.9 mV/decade). The corresponding standard potential of the electrodes during five days (n = 15) was 417 mV (SD = 3.6 mV). The water-layer test showed that the ion-selective membrane/carbon cloth interface was not subject to the formation of a water layer. The electrodes had selectivity coefficients comparable to the values obtained from the literature. The resistance of the ion-selective membrane, determined by EIS, was in the range of 45–250 MΩ for the planar electrode geometries studied in this work.

High-Performance pH Sensor Electrodes Based on a Hexagonal Pt Nanoparticle Array-Coated Nanoporous Alumina Membrane.

Porous anodic alumina membranes coated with Pt nanoparticles (PAAM/Pt) have been employed as pH sensor electrodes for H+ ion detection. The PAAM was designed using a two-step anodization process. Pt nanoparticles were then sputtered onto the membrane at different deposition times. The membrane’s morphological, chemical, and optical characteristics were carefully assessed following the fabrication stage using a variety of analytical techniques. The potential of the PAAM/Pt sensor electrode was investigated by measuring the potential using a simple potentiometric method. The effects of depositing Pt nanoparticles for 3–7 min on sensor electrode sensitivity were examined. The optimal potentiometric Nernstian response slope for the PAAM/Pt sensor electrode with 5 min Pt sputter coating is 56.31 mV/decade in the pH range of 3.0 to 10 at 293 K. Additionally, the PAAM/Pt sensor electrode’s stability and selectivity in various ions solutions were examined. The sensor electrode had a lifetime of more than six weeks and was kept in a normal air environment.