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Sprinkle formulations represent an interesting genre of medicinal products. A frequent problem, however, is the need to mask the unpleasant taste of these drug substances. In the present work, we propose the use of a novel sensor array based on solid-state ion-selective electrodes to evaluate the taste-masking efficiency of rosuvastatin (ROS) sprinkle formulations. Eight Multiple Unit Pellet Systems (MUPSs) were analyzed at two different doses (API_50) and (API_10), as well as pure Active Pharmaceutical Ingredient (API) as a bitter standard. Calcium phosphate-based starter pellets were coated with the mixture containing rosuvastatin. Some of them were additionally coated with hydroxypropyl methylcellulose, which was intended to separate the bitter substance and prevent it from coming into contact with the taste buds. The sensor array consisted of 16 prepared sensors with a polymer membrane that had a different selectivity towards rosuvastatin calcium. The main analytical parameters (sensitivity, selectivity, response time, pH dependence of potential, drift of potential, lifetime) of the constructed ion-selective electrodes sensitive for rosuvastatin were determined. The signals from the sensors array recorded during the experiments were processed using Principal Component Analysis (PCA). The results obtained, i.e., the chemical images of the pharmaceutical samples, indicated that the electronic tongue composed of the developed solid-state electrodes provided respective attributes as sensor signals, enabling both of various kinds of ROS pellets to be distinguished and their similarity to ROS bitterness standards to be tested. [ABSTRACT FROM AUTHOR]

Abstract Tulathromycin (TUL) is a widely used veterinary antibiotic for treating bovine and porcine respiratory infections. Consuming animal-derived food contaminated with this medication may jeopardize human health. This work adopted the first portable potentiometric platform for direct TUL sensing in pharmaceutical and food products. The sensor employed a plasticized PVC membrane on a glassy carbon electrode doped with calix[6]arene and multi-walled carbon nanotubes (MWCNT) in a single solid contact layer for selective binding and signal stability. Characterization via scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the material’s integrity. The MWCNT-based sensor produced a stable Nernstian response (1.0 × 10−7 to 1.0 × 10−3 M) and a limit of detection (LOD) of 9.76 × 10–8 M with instantaneous response (8 ± 2 s). IUPAC validation revealed high selectivity for TUL against interfering ions, minimal drift (0.6 mV/h), and functionality over a broad pH range (2.0–7.0), allowing direct application to dosage form, spiked milk, and liver samples. Eco-Scale, AGREE, and Whiteness assessment proved the method's ecological sustainability, economic viability, and practical feasibility, surpassing traditional approaches. Graphical Abstract

Tulathromycin (TUL) is a widely used veterinary antibiotic for treating bovine and porcine respiratory infections. Consuming animal-derived food contaminated with this medication may jeopardize human health. This work adopted the first portable potentiometric platform for direct TUL sensing in pharmaceutical and food products. The sensor employed a plasticized PVC membrane on a glassy carbon electrode doped with calix[6]arene and multi-walled carbon nanotubes (MWCNT) in a single solid contact layer for selective binding and signal stability. Characterization via scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the material's integrity. The MWCNT-based sensor produced a stable Nernstian response (1.0 × 10−7 to 1.0 × 10−3 M) and a limit of detection (LOD) of 9.76 × 10–8 M with instantaneous response (8 ± 2 s). IUPAC validation revealed high selectivity for TUL against interfering ions, minimal drift (0.6 mV/h), and functionality over a broad pH range (2.0–7.0), allowing direct application to dosage form, spiked milk, and liver samples. Eco-Scale, AGREE, and Whiteness assessment proved the method's ecological sustainability, economic viability, and practical feasibility, surpassing traditional approaches. [ABSTRACT FROM AUTHOR]

New experimental data are presented demonstrating a much stronger pH dependence of the potential of electrodes with plasticized ion exchange membranes sensitive to cations of highly lipophilic physiologically active amines than would be expected from protolytic equilibrium in solution. Using an example of a vinpocetine‐sensitive electrode, the effectiveness of the dynamic diffusion model of the boundary potential for describing the effect of pH on the form of the electrode function is demonstrated. A simple equation for estimating the effect of distribution of the molecular form of amine between the solution and the membrane phases on the lower detection limit was obtained in the framework of a stationary diffusion model. It has also been shown that the selectivity of electrodes to cations of tertiary physiologically active amines relative to inorganic ions drastically depends on the basicity of the plasticizer (up to 6 orders of magnitude), and among the commercially available ones, ortho‐nitrophenyl octyl ether is the best. Besides, this plasticizer provides the lowest detection limit (1.7×10−7 M) and the best potential reproducibility (0.06 mV) for vinpocetine‐sensitive electrode. [ABSTRACT FROM AUTHOR]

In this study, we synthesized a new thiosemicarbazone derivative molecule (5) that exhibits sensor properties. The characterization of the synthesized molecule was performed using spectroscopic methods such as 1H−, 13C–NMR, FT–IR and Q–TOF. PVC‐membrane ion‐selective sensors were prepared in which the synthesized molecule was used as an ionophore. Surface images of the prepared sensors were examined by scanning electron microscope (SEM) technique. The prepared sensors exhibited selectivity towards barium(II) ions. The developed barium(II)‐selective sensor had a low detection limit of 5.54×10−7 M in the concentration range of 1.0×10−1–1.0×10−6 M. The proposed barium(II)‐selective sensor had fast response time, good repeatability and stability, and can be manufactured with low cost. The sensor can detect barium(II) ions in various water samples with very high recoveries. [ABSTRACT FROM AUTHOR]

Ion-selective electrodes for tetrachloroaurate(III) have been developed for potentiometric monitoring of the reduction reaction of tetrachloroaurate(III). Three different plasticized polyvinyl chloride membranes containing tridodecymethylammonium chloride as an anion exchanger were investigated. These membranes differ in the plasticizer used, either 2-nitrophenyl octyl ether (NPOE) or tricresyl phosphate (TCP) or bis-(2-ethylhexyl) sebacate (DOS). The potentiometric response of the electrodes to the tetrachloroaurate(III) concentration was studied by two methods. In the first method, commonly used in the calibration of ion-selective electrodes, successive tetrachloroaurate(III) concentration increments were used and the potential was allowed to stabilize after each concentration step. The second method was developed to mimic the tetrachloroaurate(III) reduction reaction in which there is a continuous decrease in the concentration of tetrachloroaurate(III). This was achieved by continuously diluting an initial concentration of tetrachloroaurate(III) by pumping a diluent solution while keeping the sample volume constant. This method gave an excellent linear response to the tetrachloroaurate(III) concentration. The calibrated electrodes were used for the potentiometric monitoring of the kinetics of a newly observed reaction: the reduction of tetrachloroaurate(III) by hydroxylamine catalyzed by iodide. A mechanism for this reaction is proposed on the basis of the experimental results obtained. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) was used as an ion-to-electron transducer for all-solid-state nitrate electrodes based on an alkyl ammonium salt as the sensing element. Commercially available carbon screen-printed electrodes modified with GO were used as conductive substrates, whose morphology and distribution along the surface were evaluated by scanning electron microscopy and Raman spectroscopy. The potentiometric performance of the GO-based electrodes revealed a Nernstian slope of −53.5 ± 2.0 mV decade−1 (R2 = 0.9976 ± 0.0015) in the range from 3.0 × 10−6 to 10−2 M and a lower limit of detection of 1.9 × 10−6 M. An impressive reproducibility between equally prepared electrodes (n = 15) was demonstrated by a variation of <6% for the calibration parameters. Constant current chronopotentiometry and water layer tests were used to evaluate the potential signal stability, providing similar performance to previously published works with graphene-based ion-selective electrodes. Notably, the GO-based sensors showed the absence of a water layer, a long-term drift of 0.3 mV h−1, and a stable performance (LOD and sensitivity) over 3 months. The applicability of the proposed sensors was demonstrated in determining nitrate levels in water samples with great accuracy, yielding recovery values from 87.8 to 107.9%, and comparable (p > 0.05) results to a commercial nitrate probe. These findings demonstrate the use of GO as an alternative ion-to-electron transducer for the fabrication of all-solid-state potentiometric electrodes. [ABSTRACT FROM AUTHOR]

Highly selective poly(vinyl chloride) (PVC) membrane electrodes, based on oxovanadium(IV) complexes of heteromacrocyclic compounds as new iodideselective ionophores for ion-selective electrodes (ISEs), were fabricated with a composition of PVC (28.1 wt%), plasticizers (69.3 wt%), ionophores (2.6 wt%), and cation excluders (15 mol% relative to the ionophore). The electrode prepared from oxovanadium(IV) tetraphenyl porphyrin with 2-nitrophenyl octyl ether (o-NPOE) as the membrane solvent and tetradodecylammonium chloride (TDDACl) as the cation excluder was found to exhibit the best sensitivity over a wide concentration range from 5.0 × 10-7 to 2.1 × 10-2 M with a Nernstian response of -59.02 mV per decade and the highest ionselectivity toward I- ions over perchlorate ions (I-/ClO4 - = 91). [ABSTRACT FROM AUTHOR]

Plant-available nitrogen, often in the form of nitrate, is an essential nutrient for plant growth. However, excessive nitrate in the environment and watershed has harmful impacts on natural ecosystems and consequently human health. A distributed network of nitrate sensors could help to quantify and monitor nitrogen in agriculture and the environment. Here, we have developed fully printed potentiometric nitrate sensors and characterized their sensitivity and selectivity to nitrate. Each sensor comprises an ion-selective electrode and a reference electrode that are functionalized with polymeric membranes. The sensitivity of the printed ion-selective electrodes was characterized by measuring their potential with respect to a commercial silver/silver chloride reference electrode in varying concentrations of nitrate solutions. The sensitivity of the printed reference electrodes to nitrate was minimized with a membrane containing polyvinyl butyral (PVB), sodium chloride, and sodium nitrate. Selectivity studies with sulphate, chloride, phosphate, nitrite, ammonium, calcium, potassium, and magnesium showed that high concentrations of calcium can influence sensor behavior. The printed ion-selective and reference electrodes were combined to form a fully printed sensor with sensitivity of -48.0 ± 3.3 mV/dec between 0.62 and 6200 ppm nitrate in solution and -47 ± 4.1 mV/dec in peat soil.

The maintenance of ion balance in closed hydroponic solutions is essential to improve the crop quality and recycling efficiency of nutrient solutions. However, the absence of robust ion sensors for key ions such as P and Mg and the coupling of ions in fertilizer salts render it difficult to effectively manage ion-specific nutrient solutions. Although ion-specific dosing algorithms have been established, their effectiveness has been inadequately explored. In this study, a decision-tree-based dosing algorithm was developed to calculate the optimal volumes of individual nutrient stock solutions to be supplied for five major nutrient ions, i.e., NO3, K, Ca, P, and Mg, based on the concentrations of NO3, K, and Ca and remaining volume of the recycled nutrient solution. In the performance assessment based on five nutrient solution samples encompassing the typical concentration ranges for leafy vegetable cultivation, the ion-selective electrode array demonstrated feasible accuracies, with root mean square errors of 29.5, 10.1, and 6.1 mg·L-1 for NO3, K, and Ca, respectively. In a five-step replenishment test involving varying target concentrations and nutrient solution volumes, the system formulated nutrient solutions according to the specified targets, exhibiting average relative errors of 10.6 ± 8.0%, 7.9 ± 2.1%, 8.0 ± 11.0%, and 4.2 ± 3.7% for the Ca, K, and NO3 concentrations and volume of the nutrient solution, respectively. Furthermore, the decision tree method helped reduce the total fertilizer injections and carbon emissions by 12.8% and 20.6% in the stepwise test, respectively. The findings demonstrate that the decision-treebased dosing algorithm not only enables more efficient reuse of nutrient solution compared to the existing simplex method but also confirms the potential for reducing carbon emissions, indicating the possibility of sustainable agricultural development. [ABSTRACT FROM AUTHOR]

With the recent development in the field of electronics, it has made possible to continuous monitor health of patients and elderly and even of normal person. Since many years we are using bloodbased diagnosis for diagnosis of various health conditions and diseases. However, recent research done by many researchers shows that there are other potential biomarkers such as, sweat which can provide diagnosis of various health conditions and diseases. Sodium and chloride concentration in sweat provides status of hydration status in human body. Here we have designed a health monitoring device based on sweat analysis using different types of electrochemical sensors. Ion-selective electrodes for Na+ and Cl- are used which gives details about a person's hydration status and a glucose sensor is also used to measure the sweat glucose levels. The sensors are calibrated for artificial sweat solutions with different concentrations of Na+, Cl- and glucose. On body testing is done to confirm functionality of designed system for sweat analysis. The system is compact so can be used as a wearable device that is capable of continuously monitoring and wirelessly transmitting sensor data to the personal computer or smartphone. [ABSTRACT FROM AUTHOR]

In this paper, ion-selective electrodes sensitive to copper(II) ions are presented, in which new composite, synthesized from copper(II) oxide nanoparticles (CuONPs) and multi-walled carbon nanotubes (MWCNTs), was used as a solid contact. For comparison, electrodes obtained using separate components of the nanocomposite, i.e., CuONPs and MWCNTs, as well as unmodified electrodes, were also studied. The tested nanomaterials have been applied in two ways: as an intermediate layer placed between the ion-sensitive membrane and the internal electrode, and as an additional component of the ion-selective membrane mixture. To investigate the influence of the electrode's structure modification, the selected analytical parameters obtained by potentiometric measurements (slope, linearity range, detection limit, potential stability, and reversibility) and electrochemical impedance spectroscopy measurements (membrane resistance and charge transfer resistance as well as double layer capacitance) were determined and compared. It was found that the use of all nanomaterials improves the properties of the electrodes, with the effect being the strongest for electrodes modified with the CuO-MWCNTs nanocomposite. The nanocomposite-based electrodes, both those with an intermediate layer and those with a nanocomposite-modified membrane, showed a Nernstian slope of the characteristic, a wider working range and a lower detection limit compared to unmodified electrodes. Moreover, application of all nanomaterials, especially nanocomposite resulted in improvement of both, stability and reversibility of the sensor potential. Modification of the electrodes did not make them sensitive to changing external measurement conditions (lighting, presence of gasses, redox potential). The electrode with the best parameters (based on nanocomposite) was successfully used to determine the Cu2+ ions content in tap water and mineral water, obtaining satisfactory results. [ABSTRACT FROM AUTHOR]

Ion-selective electrodes for tetrachloroaurate(III) have been developed for potentiometric monitoring of the reduction reaction of tetrachloroaurate(III). Three different plasticized polyvinyl chloride membranes containing tridodecymethylammonium chloride as an anion exchanger were investigated. These membranes differ in the plasticizer used, either 2-nitrophenyl octyl ether (NPOE) or tricresyl phosphate (TCP) or bis-(2-ethylhexyl) sebacate (DOS). The potentiometric response of the electrodes to the tetrachloroaurate(III) concentration was studied by two methods. In the first method, commonly used in the calibration of ion-selective electrodes, successive tetrachloroaurate(III) concentration increments were used and the potential was allowed to stabilize after each concentration step. The second method was developed to mimic the tetrachloroaurate(III) reduction reaction in which there is a continuous decrease in the concentration of tetrachloroaurate(III). This was achieved by continuously diluting an initial concentration of tetrachloroaurate(III) by pumping a diluent solution while keeping the sample volume constant. This method gave an excellent linear response to the tetrachloroaurate(III) concentration. The calibrated electrodes were used for the potentiometric monitoring of the kinetics of a newly observed reaction: the reduction of tetrachloroaurate(III) by hydroxylamine catalyzed by iodide. A mechanism for this reaction is proposed on the basis of the experimental results obtained.

Graphene oxide (GO) was used as an ion-to-electron transducer for all-solid-state nitrate electrodes based on an alkyl ammonium salt as the sensing element. Commercially available carbon screen-printed electrodes modified with GO were used as conductive substrates, whose morphology and distribution along the surface were evaluated by scanning electron microscopy and Raman spectroscopy. The potentiometric performance of the GO-based electrodes revealed a Nernstian slope of −53.5 ± 2.0 mV decade−1 (R2 = 0.9976 ± 0.0015) in the range from 3.0 × 10−6 to 10−2 M and a lower limit of detection of 1.9 × 10−6 M. An impressive reproducibility between equally prepared electrodes (n = 15) was demonstrated by a variation of −1, and a stable performance (LOD and sensitivity) over 3 months. The applicability of the proposed sensors was demonstrated in determining nitrate levels in water samples with great accuracy, yielding recovery values from 87.8 to 107.9%, and comparable (p > 0.05) results to a commercial nitrate probe. These findings demonstrate the use of GO as an alternative ion-to-electron transducer for the fabrication of all-solid-state potentiometric electrodes.

Potentiometric ion-selective electrode (ISE) sensors are powerful electrochemical tools used in various applications in different fields, including the biological, clinical, and environmental fields, owing to their high selectivity, sensitivity, simplicity, and versatility. This review highlights recent advancements in ionophore-based polymeric ISE sensors over the past five years, with a particular focus on progress at the micro- and nanoscales. After discussing the conventional ISE configuration and its general operational principles, we explore the notable advancements in terms of the key ion-selective membrane components, such as ionophores, and other techniques combined with ISEs. These advancements have significantly improved the sensing performances and expanded the practical applications. We also examine the progress in the field of miniaturized solid-contact microelectrodes and the incorporation of novel functional materials for efficient ion-to-electron transduction. Miniaturized solid-state ISEs provide low limits of detection with reduced sample volume requirements, extended stability, and rapid response times. When combined with scanning electrochemical microscopy, ion-selective microelectrodes enable highly spatially resolved ion analyses. The integration of solid-contact ISEs into compact, portable, wearable devices has advanced the field of wearable on-body ISE sensors. Finally, we briefly introduce the development of ion-selective optode sensors as promising optical sensors based on ionophores that are particularly advantageous for cellular imaging.

Background: Ionophores in the composition of potentiometric ion‐selective electrodes interact directly with the analyte ion and enable the determination of ionic species in various samples. Objectives: In this study, a novel ion‐selective electrode based on 5‐bromosalicylaldehyde thiosemicarbazone was developed for the selective determination of Cr3+ ions. Methods: The optimum electrode composition contained ionophore, poly (vinyl chloride) (PVC), bis (2‐ethylhexyl) sebacate (BEHS) and potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) in ratios of 4.0: 61.0: 34.0: 1.0 (mg), respectively. Potential measurements were performed using a computer‐controlled multi‐channel potentiometric measurement system. Results: The developed Cr (III)‐selective electrode exhibited a low detection limit of 3.96 × 10−6 M over a wide concentration range of 1.0 × 10−5 – 1.0 × 10−1 M (R2: 0.9979). The electrode exhibited good selectivity towards Cr3+ ions among metal ions with different charges. The chromium (III)‐selective electrode, which exhibited highly reproducible results in three different concentration ranges, also had a very fast response time of 5 s. Conclusions: The developed Cr (III)‐selective electrode were successfully performed in various beverage samples. As a result, the proposed electrode can be an alternative to other analytical methods in the analysis of Cr3+ ions. [ABSTRACT FROM AUTHOR]

The use of solid‐contact ion‐selective electrodes (ISEs) is of interest to many clinical, environmental, and industrial applications. However, upon extended exposure to samples and under thermal and mechanical stress, adhesion between these membranes and underlying substrates often weakens gradually. Eventually, this results in the formation of a water layer at the interface to the underlying electron conductor and in delamination of the membrane from the electrode body, both major limitations to long‐term monitoring. To prevent these problems without increasing the complexity of design with a mechanical attachment, we use photo‐induced graft polymerization to simultaneously attach ionophore‐doped crosslinked poly(decyl methacrylate) sensing membranes covalently both to a high surface area carbon as ion‐to‐electron transducer and to inert polymeric electrode body materials (i.e., polypropylene and poly(ethylene‐co‐tetrafluoroethylene)). The sensors provide high reproducibility (standard deviation of E0 of 0.2 mV), long‐term stability (potential drift 7 μV h−1 over 260 h), and resistance to sterilization in an autoclave (121 °C, 2.0 atm for 30 min). For this work, a covalently attached H+ selective ionophore was used to prepare pH sensors with advantages over conventional pH glass electrodes, but similar use of other ionophores makes this approach suitable to the fabrication of ISEs for a variety of analytes. [ABSTRACT FROM AUTHOR]

Potentiometric sensors are the largest and most commonly used group of electrochemical sensors. Among them, ion-selective electrodes hold a prominent place. Since the end of the last century, their re-development has been observed, which is a consequence of the introduction of solid contact constructions, i.e., electrodes without an internal electrolyte solution. Research carried out in the field of potentiometric sensors primarily focuses on developing new variants of solid contact in order to obtain devices with better analytical parameters, and at the same time cheaper and easier to use, which has been made possible thanks to the achievements of material engineering. This paper presents an overview of new materials used as a solid contact in ion-selective electrodes over the past several years. These are primarily composite and hybrid materials that are a combination of carbon nanomaterials and polymers, as well as those obtained from carbon and polymer nanomaterials in combination with others, such as metal nanoparticles, metal oxides, ionic liquids and many others. Composite materials often have better mechanical, thermal, electrical, optical and chemical properties than the original components. With regard to their use in the construction of ion-selective electrodes, it is particularly important to increase the capacitance and surface area of the material, which makes them more effective in the process of charge transfer between the polymer membrane and the substrate material. This allows to obtain sensors with better analytical and operational parameters. Brief characteristics of electrodes with solid contact, their advantages and disadvantages, as well as research methods used to assess their parameters and analytical usefulness were presented. The work was divided into chapters according to the type of composite material, while the data in the table were arranged according to the type of ion. Selected basic analytical parameters of the obtained electrodes have been collected and summarized in order to better illustrate and compare the achievements that have been described till now in this field of analytical chemistry, which is potentiometry. This comprehensive review is a compendium of knowledge in the research area of functional composite materials and state-of-the-art SC-ISE construction technologies. [ABSTRACT FROM AUTHOR]

Electrochemical sensors have the ability to convert the electrochemical reaction that occurs between the analyte and the electrode into a useful signal. Potentiometric sensors, ion-selective electrodes, an important member of the electrochemical sensor family, have been the focus of much research for almost a century. Their constant development and combination with the development of other scientific and technological fields have given them a wide range of applications. Properties of ion-selective electrodes, such as simplicity of method, low cost, small sensor size, fast response, and reliability, have made them valuable competitors of other methods for determining the concentration of analytes in different real samples with minimal or no pretreatment of the samples. Considering the wide distribution and great importance of iron(III) cations in the human body and environment, there is a great need to develop analytical tools for their rapid and efficient determination. This paper, presents different literature sources dealing with the development of potentiometric sensors for the determination of iron(III) cations, focusing on scientific papers published in the last decade. The active centre of the sensor, its linear dynamic range, the limit of detection, and the change in potential depending on the change in analyte concentration are shown. It has been found that Fe3+ cations can be determined successfully in numerous real samples, such as pharmaceutical preparations, biological samples, different water samples (drinking, waste, mineral...), food products such as green and black tea, etc. Thanks to the wide linear range, low detection limits, and a wide range of real samples in which they can be applied, ion-selective electrodes are promising candidates for replacing some more sophisticated methods for the determination of iron(III) cations. [ABSTRACT FROM AUTHOR]

Nitrogen is a vital ingredient for plant development and growth. It is one of the most crucial indicators of soil fertility and crop growth conditions. For the monitoring of nitrogen loss patterns and the development of crop nitrogen fertilizer application strategies, an accurate determination of soil nitrogen concentration can be a valuable source of information. For the advancement of precision agriculture and the preservation of the natural ecological environment, an accurate, quick, and low-cost determination of soil nitrogen content and its variations is essential. This paper systematically analyzes and summarizes soil nitrogen detection methods by compiling and analyzing the relevant literature, comparing the advantages and disadvantages of various methods, and concluding with a discussion of the most significant challenges and future research trends in this field. This study provides a helpful resource for understanding the current status, application constraints, and future developments of nitrogen-sensing technologies in precision agriculture. [ABSTRACT FROM AUTHOR]

Nitrate sensing is an important application for potentiometry in environmental applications. Its recognition is by ion‐exchangers whose selectivity is governed by the lipophilicity of the ions in solution. Yet, considerable research efforts have been dedicated to the development of such ionophores and some have already been commercialized. This work examines two commercially available nitrate ionophores, nitrate ionophores V and VI, and compares their performance with widely used ion‐exchangers by determining the resulting membrane selectivity and complexation to nitrate. Unfortunately, adding a nitrate ionophore to the membrane did not result in improved selectivity. Sandwich membrane experiments indicated that binding interaction is too weak to be measurable, with a logarithmic formation constant of just 1.36±0.14 for ionophore V with nitrate. Ways to improve the reporting of relevant data are suggested. [ABSTRACT FROM AUTHOR]

The evaluation of the biogenic amines (BAs) profile of different types of craft beers is herein presented. A previously developed and validated analytical method based on ion-pair chromatography coupled with potentiometric detection was used to determine the presence of 10 BAs. Good analytical features were obtained for all amines regarding linearity (R2 values from 0.9873 ± 0.0015 to 0.9973 ± 0.0015), intra- and inter-day precision (RSD lower than 6.9% and 9.7% for beer samples, respectively), and accuracy (recovery between 83.2–108.9%). Detection and quantification limits range from 9.3 to 60.5 and from 31.1 to 202.3 µg L−1, respectively. The validated method was applied to the analysis of four ale beers and one lager craft beer. Ethylamine, spermidine, spermine, and tyramine were detected in all analyzed samples while methylamine and phenylethylamine were not detected. Overall, pale ale beers had a significantly higher total content of BAs than those found in wheat pale and dark samples. A general least square regression model showed a good correlation between the total content of BAs and the brewing process, especially for Plato degree, mashing, and fermentation temperatures. Knowledge about the type of ingredients and manufacturing processes that contribute to higher concentrations of these compounds is crucial to ensuring consumer safety. [ABSTRACT FROM AUTHOR]

Epilepsy is a chronic neurological disease and its treatment requires the use of anti-epileptic drugs. The determination of anti-epileptic drugs in pharmaceutical and biological samples is carried out using various analytical methods. Potentiometric methods, which have a very important place in electroanalytical chemistry, are used extensively in the determination of various drugs in biological and pharmaceutical samples. In this study, we reviewed potentiometry-based sensors developed for the determination of anti-epileptic drug molecules in biological and pharmaceutical samples. [ABSTRACT FROM AUTHOR]

• Development of low-cost ion-selective electrodes made from disposable syringes. • Standard quantification of potassium is not precise for samples of high ionic strength. • Two electrodes coupled with ensemble random forest model greatly enhance precision. • Potassium was quantified in food and pharmaceutical supplements without recalibration. • Similar performance can be achieved with lower-cost ionophores using auxiliary sensors. Over the years, ion-selective electrodes (ISEs) have become routine means of analysis for industrial, environmental, and clinical applications, allowing for rapid, non-invasive, and easy disease monitoring and diagnostics. Their enormous advantages include wide dynamic range, ease of operation and low detector cost. Sets of ion-selective electrodes selective towards various ions can easily be assembled into an electronic tongue system. The additional information gained from other electrodes can help overcome the ISE's inherent limitations, such as the need for recalibration in more complex samples of variable ionic strength. In this work we developed low-cost ion-selective electrodes made from disposable syringes equipped with plasticized PVC membranes. To characterize the system we have chosen well-studied ionophore valinomycin, and the results in model solutions were comparable to standard ISE electrodes fabricated using commercial bodies. However, quantification of potassium in real samples showed, as expected, that measurement in complex, more concentrated solutions of higher ionic strength, such as beetroot soup, tomato-based food products, and dried fruits, are reproducible but subject to relative error up to 76 %. To overcome this limitation, we have constructed an electronic tongue based on the low-cost syringe electrodes. Different compositions of the array were tested with a series of multivariate algorithms. We have shown that adding a single type of electrode coupled with an ensemble random forest model allows us to quantify potassium in a wide range of food products, and pharmaceutical supplements without recalibration. Compared to a quantification of potassium using a standard calibration curve, the root mean square error of prediction was almost six times lower. We have also shown how the array can be designed to achieve comparable analytical performance using less selective ionophores, such as dibenzo-18-crown-6 instead of valinomycin. [Display omitted] [ABSTRACT FROM AUTHOR]

The potentiometric response of ion-selective electrodes (ISEs) with membranes simultaneously containing two ionophores: valinomycin and lithium ionophore Li VIII, as well as the cation exchanger potassium tetrakis(p-Cl-phenyl) borate in different concentrations is studied in KCl, LiCl and KCl + LiCl solutions. It is shown that ISEs with a membrane containing an excess of ionophores over the ion-exchanger provide Nernstian response to K+ and to Li+ ions. However, membranes with an excess of the ion-exchanger over valinomycin show Nernstian response to K+ only in mixed KCl + LiCl solutions with constant ratios of the concentrations of these electrolytes. On the contrary, the response to Li+ is obtained both in mixed and pure LiCl solutions. The results are semi-quantitatively explained using a simple mathematical model and respective computer simulation. [Display omitted] • Potentiometric response of ISEs with two ionophores and excess of ion-exchanger. • Valinomycin and Li VIII: non-Nernstian response in KCl, Nernstian in LiCl. • Nernstian response to K+ and to Li+ in mixed KCl + LiCl solutions. • Response to more strongly complexed ion (K+) is more prone to ion-exchanger excess. • Semi-quantitative explanation by computer simulations. [ABSTRACT FROM AUTHOR]

Epilepsy is a chronic neurological disease and its treatment requires the use of anti–epileptic drugs. The determination of anti–epileptic drugs in pharmaceutical and biological samples is carried out using various analytical methods. Potentiometric methods, which have a very important place in electroanalytical chemistry, are used extensively in the determination of various drugs in biological and pharmaceutical samples. In this study, we reviewed potentiometry–based sensors developed for the determination of anti–epileptic drug molecules in biological and pharmaceutical samples.

This work is a mini-review highlighting the relevance of the θ metallabis(dicarbollide) [3,3′-Co(1,2-C2B9H11)2]− with its peculiar and differentiating characteristics, among them the capacity to generate hydrogen and dihydrogen bonds, to generate micelles and vesicles, to be able to be dissolved in water or benzene, to have a wide range of redox reversible couples and many more, and to use these properties, in this case, for producing potentiometric membrane sensors to monitor amine-containing drugs or other nitrogen-containing molecules. Sensors have been produced with this monoanionic cluster [3,3′-Co(1,2-C2B9H11)2]−. Other monoanionic boron clusters are also discussed, but they are much fewer. It is noteworthy that most of the electrochemical sensor species incorporate an ammonium cation and that this cation is the species to be detected. Alternatively, the detection of the borate anion itself has also been studied, but with significantly fewer examples. The functions of the borate anion in the membrane are different, even as a doping agent for polypyrrole which was the conductive ground on which the PVC membrane was deposited. Apart from these cases related to closo borates, the bulk of the work has been devoted to sensors in which the θ metallabis (dicarbollide) [3,3′-Co(1,2-C2B9H11)2]− is the key element. The metallabis (dicarbollide) anion, [3,3′-Co(1,2-C2B9H11)2]−, has many applications; one of these is as new material used to prepare an ion-pair complex with bioactive protonable nitrogen containing compounds, [YH]x[3,3′-Co(1,2-C2B9H11)2]y as an active part of PVC membrane potentiometric sensors. The developed electrodes have Nernstian responses for target analytes, i.e., antibiotics, amino acids, neurotransmitters, analgesics, for some decades of concentrations, with a short response time, around 5 s, a good stability of membrane over 45 days, and an optimal selectivity, even for optical isomers, to be used also for real sample analysis and environmental, clinical, pharmaceutical and food analysis. [ABSTRACT FROM AUTHOR]

The radioactive and hazardous nature of thorium demands the fabrication of efficient electrodes for its sensitive and selective monitoring in aqueous environments. The present paper reports the construction and characterization of a new carbon paste electrode (CPE) chemically modified by octyl phenyl acid phosphate (OPAP) as a selective recognition agent for the potentiometric assay of thorium(IV) ions. Improved sensitivity, electrical conductivity, and selectivity were achieved by incorporating oxidized multi-walled carbon nanotubes (o-MWCNTs) into the carbon paste composition. The electrochemical performance of the developed electrode was evaluated regarding the paste ingredients, response time, and working pH range. The standard CPE potentials, E°, were determined at various temperatures and the isothermal temperature coefficient was calculated. The optimized CPE showed a Nernstian slope of 14.65 ± 0.38 mV decade−1 over the concentration range of 4.82 × 10–7–1.00 × 10–1 mol L−1. The electrode possessed a short response time (9 s), independence of the solution pH over the range of 2.5–5.5, and a relatively long operational lifetime (˃ 3 months). The selectivity coefficients indicated the good discrimination ability of the developed CPE towards thorium(IV) ion compared to various common ions. Aiming to judge the practical utility of the developed CPE, it was successfully used for the potentiometric analysis of thorium(IV) ions in various real aqueous matrices with sensible results. [ABSTRACT FROM AUTHOR]

Many healthcare and environmental monitoring devices use electrochemical techniques to detect and quantify analytes. With sensors progressively becoming smaller—particularly in point‐of‐care (POC) devices and wearable platforms—it creates the opportunity to operate them using less energy than their predecessors. In fact, they may require so little power that can be extracted from the analyzed fluids themselves, for example, blood or sweat in case of physiological sensors and sources like river water in the case of environmental monitoring. Self‐powered electrochemical sensors (SPES) can generate a response by utilizing the available chemical species in the analyzed liquid sample. Though SPESs generate relatively low power, capable devices can be engineered by combining suitable reactions, miniaturized cell designs, and effective sensing approaches for deciphering analyte information. This review details various such sensing and engineering approaches adopted in different categories of SPES systems that solely use the power available in liquid sample for their operation. Specifically, the categories discussed in this review cover enzyme‐based systems, battery‐based systems, and ion‐selective electrode‐based systems. The review details the benefits and drawbacks with these approaches, as well as prospects of and challenges to accomplishing them. [ABSTRACT FROM AUTHOR]

Monitoring lithium ions (Li + ) in lithium-rich brine (LrB) is critical for metal recovery, yet challenges such as high ionic strength and gypsum-induced surface deterioration hinder the performance of potentiometric ion-selective electrode (ISE) sensors. This study advances the functionality of Li + ISE sensors and enables continuous monitoring of Li + concentration in LrB by introducing apolyelectrolyte multilayer (PEM) of poly(allylamine hydrochloride)/poly(sodium 4-styrenesulfonate) (PAH/PSS) that serves as an antigypsum scaling material to minimize nucleation on the sensor surface. With 5.5 bilayers of PAH/PSS coating, the Li + ISE sensors possess a high Nernst slope (59.14 mV/dec), rapid response (<10 s), and superior selectivity against competitive ions (Na + , log K s = -2.35; K + , log K s = -2.47; Ca 2+ , log K s = -4.05; Mg 2+ , log K s = -4.18). The impedance (85.1 kΩ) of (PAH/PSS) 5.5 -coated sensors is 1 order of magnitude lower than that of electrospray ion-selective membrane (E-ISM) Li + sensors (830 kΩ), attributed to the ultrathin (45.3 nm) and highly dielectric PAH/PSS bilayers. During a 15-day continuous monitoring test in LrB, the (PAH/PSS) 5.5 -coated Li + ISE sensors with their superhydrophilic and smooth surface diminish nucleation sites for scaling agents (e.g., Ca 2+ and SO 4 2- ) and consequently mitigate gypsum scaling. Moreover, a brine-tailored denoising data processing algorithm (bt-DDPA), coupled with the salinity-adjusted mathematical model with Lagrange interpolation, effectively captures Li + fluctuation by filtering out anomalies and reducing sensor drift in brine. Bt-DDPA alleviates the discrepancy between the sensor readings and the lab-based validation results by 46.06%. This study demonstrates that the integration of material advancement (PAH/PSS coating) with sensor data processing (bt-DDPA) bolsters continuous and accurate Li + monitoring in LrB, crucial for brine water treatment and resource recovery.

Monitoring potassium ion (K + ) concentration is essential in veterinary medicine, particularly for preventing hypokalemia in dairy cows, which can severely impact their health and productivity. While traditional laboratory methods like atomic absorption spectrometry are accurate, they are also time-consuming and require complex sample preparation. Ion-selective electrodes (ISEs) provide an alternative that is faster and more suitable for field measurements, but their performance is often compromised under variable temperature conditions, leading to inaccuracies. To address this, we developed a novel screen-printed ion-selective electrode (SPE) with hydrophobic Ti 3 C 2 Mxene and gold nanoparticles (AuNPs), integrated with a temperature sensor. This design improves stability and accuracy across fluctuating temperatures by preventing water layer formation and enhancing conductivity. The sensor was validated across temperatures from 5 °C to 45 °C, achieving a linear detection range of 10 - ⁵ to 10 -1 M and a response time of approximately 15 s. It also demonstrated excellent repeatability, selectivity, and stability, making it a robust tool for K + monitoring in complex environments. This advancement could lead to broader applications in other temperature-sensitive analytical fields.

Introduction: Discrepancies between electrolyte concentrations determined by blood gas analysers (BGA) and core-lab chemistry analysers may create confusion in clinical practice. This problem is rooted in the different ion-selective electrode (ISE) methodologies that are used. Whilst most available chemistry analysers use indirect ISE, we evaluated the analytical performance of the new automated chemistry analyser Biossays™ E6 (Snibe), equipped with direct ISE, for the determination of sodium (Na + ), potassium (K + ), chloride (Cl - ), ionized calcium (iCa 2+ ) and pH., Materials and Methods: Total precision, estimated deviation and total error were evaluated for all analytes on the E6 analyser. Several patient cohorts were used to perform method comparisons between the E6 and the direct (RP500e BGA) and indirect (Architect c16000 analyser) ISE methods routinely used in the lab. Obtained data were compared against pre-set quality specifications and used for adjustment of the 2 direct ISE methods. For Na + and iCa 2+ , agreement with the routinely used protein-corrected Na + and total calcium (TCa 2+ ) concentrations were assessed respectively., Results: The analytical performance for the 4 tested electrolytes (Na + , K + , Cl - , iCa 2+ ) and pH were acceptable and within the specified performance specifications. After adjustment of both direct methods, method comparison on an independent patient cohort showed good agreement. For Na + and iCa 2+ , a good correlation with the protein corrected Na + and TCa 2+ results was observed., Conclusion: The acceptable analytical performance and ease-of-use of the E6 direct ion selective instrument is making it feasible to optimize electrolyte determinations to direct methodology., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Nowadays, using a potentiometric ion sensor to achieve detection of biological analytes is still a big challenge, since these analytes usually do not yield a measurable ion signal. To address this challenge, a simple and robust potentiometric sensing protocol based on a delayed Nernstian response is proposed for the label-free detection of biological analytes. The proposed sensor platform is composed of two layers: the surface recognition layer and the indicator-ion-selective electrode (ISE) membrane layer. It is based on a surface blocking mechanism in which the surface recognition interactions between the surface recognition element and the target can impede the diffusion of the indicator ion from the aqueous phase to the sensing membrane phase to reach the final Nernstian-response equilibrium, thus resulting in a delayed potential change. Such a potential change could be used to measure the concentration of a biological target in the sample. Thus, a sensing system was designed by using phage MS2, its host bacterium Escherichia coli ATCC 15597(abbreviated as E. coli H), and a solid-contact butyrylcholine ISE as a surface recognition element, a target, and an indicator electrode, respectively. This new concept offers a simple, sensitive, and extremely selective potentiometric method for detection of E. coli H with a detection limit of 100 CFU mL -1 . It can be expected that the present approach may pave the way to using ISEs to detect various important nonionic biological targets in clinical and environmental applications.

The monitoring of ion homeostasis in vivo is of paramount importance due to its critical functions in biological systems. However, current leading technologies for creating ion-selective electrodes often fall short of the requirements for in vivo applications in terms of multiplexity, miniaturization, and flexibility. To address this gap, we introduce an integrated multiplexed ion monitoring probe created from thermally drawn multi-electrode polymer fiber, aimed at enhancing in vivo ion homeostasis studies. This probe employs a carbon nanofiber (CNF)/graphene composite as the sensing material, utilizing a thermal drawing process, laser machining, and material functionalization to fabricate multiplexed ion probes. Our design incorporates electrodes on micron-scale fibers for sensing Na + , K + and Cl - ions, alongside an electrode for electrophysiology recording, achieving excellent sensitivity, stability, selectivity, and reversibility in distilled water and artificial cerebrospinal fluid solutions (aCSF). These results demonstrate the potential of the probe for future in vivo applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The aim of this paper is to investigate the influence of the molecules of conducting polymers on the properties of potentiometric sensors. Two conducting polymers, poly(3-octylthiophene-2,5-diyl) and poly(3,4-ethylene-1,4-dioxythiophene), were compared in the context of the design of ion-selective electrodes. This study offers a comparison of the most popular conducting polymers in the context of the design of potentiometric sensors. Firstly, the properties of both materials, such as their microstructure, electrical performance, wettability, and thermic properties, were examined. Subsequently, conducting polymers were applied as transducer layers in potassium-selective sensors. The properties of both groups of sensors were evaluated using the potentiometry method. Research has shown that the presence of poly(3-octylthiophene-2,5-diyl) (POT) in the transducer layer makes it superhydrophobic, leading to a long lifetime of sensors. On the other hand, the addition of poly(3,4-ethylene-1,4-dioxythiophene) polystyrene sulfonate (PEDOT:PSS) allows for the enhancement of electrical capacitance parameter values, which beneficially influence the stability of the potentiometric response of sensors. Both examined conducting polymers turned out to be perfect materials for transducer layers in potentiometric sensors, each being responsible for enhancing different properties of electrodes.

Objective: This study investigated the prevalence of water filtration and purification system (WFPS) use among residents of central Indiana (USA) and determined the effects of WFPS on the concentrations of fluoride, calcium, magnesium, potassium, and sodium in tap water., Methods: A census-based questionnaire collected data on demographics, water use, and water sources. Participants were also asked to provide water samples from their tap water or the WFPS they used. Water samples were analyzed using ion-specific electrodes (fluoride) and atomic absorption spectrometry (metals). Mineral concentration comparisons between water sources used nonparametric tests; questionnaire associations were testing using correlations, chi-square tests, and nonparametric tests., Results: One hundred and one participants completed the study, of which 71 % used some type of WFPS. Blacks were less likely to use WFPS than Asian or White participants (p = 0.045). Those with bachelor's degrees or higher were more likely to use WFPS (p = 0.003). The most used WFPS were pitcher filters (31 %), water softeners (21 %), reverse osmosis systems (11 %), faucet-mounted filters (4 %), and whole-house carbon filters (1 %). Reverse osmosis systems resulted in the lowest mineral concentrations (median, ppm; F-0.08, Ca-2.30, Mg-0.46, Na-4.60, P-0.35). Pitcher filters were largely comparable to unfiltered tap water. Water softeners resulted in the highest sodium concentrations (78.40 ppm)., Conclusion: A large proportion of study participants use WFPS, with pitcher filters being the most common. Reverse osmosis systems had the most significant impact on reducing mineral levels in tap water, while pitcher filters do not adversely affect mineral concentrations., Clinical Significance: Understanding how different WFPS affect the various minerals in tap water is essential for helping consumers in choosing the right system and for oral care providers to guide patients on water consumption and the need for fluoride supplementation, especially for those at high risk of dental caries., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objective: To develop a novel and biocompatible copper tetraamine fluoride (CTF) with antibacterial and nondiscolouring properties., Method: This study used copper fluoride and ammonia solution to develop CTF solution. The CTF was characterized by X-ray photoelectron spectroscopy (XPS). Cytotoxicity was evaluated by stem cells from human exfoliated deciduous teeth (SHED) and human gingival fibroblasts (HGF-1). The fluoride concentration was determined using ion-selective electrode. The alkalinity was measured by a pH electrode. The human dentine blocks were treated with CTF and then incubated with Streptococcus mutans to evaluate the antimicrobial and discolouring effects. The silver diamine fluoride (SDF) was employed as the positive control, and water was the negative control. The colony-forming units (CFUs) and confocal laser scanning microscopy (CLSM) were used to examine the kinetics and viability of the biofilm. The discolouring property on dentine was assessed by spectrophotometry. One-way analysis of variance with the Bonferroni post hoc test was performed to assess and compare the data., Results: XPS confirmed synthesis of CTF solution. The half-maximal inhibitory concentration of CTF on SHED and HGF-1 was 195±16 ppm and 137±11 ppm. The fluoride concentration was 121,000±5,000 ppm. The pH value was 9. Log 10 CFU of the CTF, SDF and water group were 5.0 ± 0.2, 4.9 ± 0.1 and 7.4 ± 0.1 (p < 0.001, CTF, SDFWater). Spectrophotometry showed that the ΔE of the CTF, SDF and water group were 5 ± 2, 6 ± 3 and 45±2 (p < 0.001, CTF, Water

Abstract Many healthcare and environmental monitoring devices use electrochemical techniques to detect and quantify analytes. With sensors progressively becoming smaller—particularly in point‐of‐care (POC) devices and wearable platforms—it creates the opportunity to operate them using less energy than their predecessors. In fact, they may require so little power that can be extracted from the analyzed fluids themselves, for example, blood or sweat in case of physiological sensors and sources like river water in the case of environmental monitoring. Self‐powered electrochemical sensors (SPES) can generate a response by utilizing the available chemical species in the analyzed liquid sample. Though SPESs generate relatively low power, capable devices can be engineered by combining suitable reactions, miniaturized cell designs, and effective sensing approaches for deciphering analyte information. This review details various such sensing and engineering approaches adopted in different categories of SPES systems that solely use the power available in liquid sample for their operation. Specifically, the categories discussed in this review cover enzyme‐based systems, battery‐based systems, and ion‐selective electrode‐based systems. The review details the benefits and drawbacks with these approaches, as well as prospects of and challenges to accomplishing them.

Electrophysiology and neurochemicals such as Ca2+, K+, and Na+ on the cerebral cortex can synergistically reflect the neurophysiological states. Transparent electrodes have been reported to record electrocorticography (ECoG) and image Ca2+ on the cerebral cortex surface. However, Ca2+ imaging is unable to track extracellular changes correlated with neural activities such as anesthesia, and imaging techniques to monitor K+ and Na+ are yet unavailable. Here, a flexible multifunctional electrode (FME) based on carbon nanotube array is presented to record ECoG and extracellular ions of Ca2+, K+, and Na+. The FME exhibits both lower impedance and higher capacitance than that of conventional gold electrodes. It simultaneously shows stable ion‐sensing performance and long‐term biocompatibility. The FME realizes multi‐model recording of ECoG and extracellular ions on the cerebral cortex surface of rats, providing an effective detection method for brain science. [ABSTRACT FROM AUTHOR]

In this study, a novel PVC‐based membrane containing (E)‐2‐(1‐(4‐(3‐(4‐chlorophenyl)ureido)phenyl)ethylidene)hydrazine carbothioamide (5) as an electroactive component (ionophore) along with potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) and bis(2‐ethylhexyl)adipate (DEHA) in the ratio 4.0 : 32.0 : 1.0 : 63.0 (ionophore:PVC:KTpClPB:DEHA) (w/w) was used to develop a lead(II)‐selective potentiometric sensor. The sensor exhibited a Nernstian response over a wide concentration range from 1.0×10−5 to 1.0×10−1 mol L−1 with a slope of 28.0±2.0 mV/decade, and a detection limit of 1.65×10−6 mol L−1. It displayed very good selectivity towards Pb(II) ions over other cationic species. The lead(II)‐selective sensor showed a fast response time of 5 s, good repeatability, and it worked in the broad pH range of 5.0–11.0. The sensor could be used as an indicator electrode in the quantification of Pb(II) by potentiometric titration against ethylenediaminetetraacetic acid (EDTA). In addition, this sensor was applied for the direct determination of Pb(II) in different water samples including spring water, purification water, commercial water, waste water and in a waste battery sample. [ABSTRACT FROM AUTHOR]

The valence state of copper and the composition of the surface of the membranes of film electrodes with the composition CuI–AgI–As2Se3 are studied. Using X-ray photoelectron spectroscopy, it is shown that in CuI–AgI–As2Se3 chalcogenide films the copper atom is in the Cu(I) state. Auger-electron spectroscopy is used to prove the applicability of the modified surface layer model to explain the ion sensitivity of chalcogenide film sensors. [ABSTRACT FROM AUTHOR]

One of the main methods for separation and concentration of radionuclides is liquid extraction. Selectivity is one of the most important characteristics of extraction systems potentially suitable for separating elements with similar properties. We suggest a method for determining the selectivity of extraction systems by measuring the selectivity coefficients of ion-selective electrodes (ISEs). Polypropylene paper impregnated with an organic phase was used as the electrode membrane. Di-tert-butyldicyclohexano-18-crown-6 (DTBDCH18C6) and di-tert-butyldibenzo-18-crown-6 (DTBDB18C6) crown ethers in perfluorinated diluents were used as extractants. [ABSTRACT FROM AUTHOR]

Potentiometric sensors are the largest and most commonly used group of electrochemical sensors. Among them, ion-selective electrodes hold a prominent place. Since the end of the last century, their re-development has been observed, which is a consequence of the introduction of solid contact constructions, i.e., electrodes without an internal electrolyte solution. Research carried out in the field of potentiometric sensors primarily focuses on developing new variants of solid contact in order to obtain devices with better analytical parameters, and at the same time cheaper and easier to use, which has been made possible thanks to the achievements of material engineering. This paper presents an overview of new materials used as a solid contact in ion-selective electrodes over the past several years. These are primarily composite and hybrid materials that are a combination of carbon nanomaterials and polymers, as well as those obtained from carbon and polymer nanomaterials in combination with others, such as metal nanoparticles, metal oxides, ionic liquids and many others. Composite materials often have better mechanical, thermal, electrical, optical and chemical properties than the original components. With regard to their use in the construction of ion-selective electrodes, it is particularly important to increase the capacitance and surface area of the material, which makes them more effective in the process of charge transfer between the polymer membrane and the substrate material. This allows to obtain sensors with better analytical and operational parameters. Brief characteristics of electrodes with solid contact, their advantages and disadvantages, as well as research methods used to assess their parameters and analytical usefulness were presented. The work was divided into chapters according to the type of composite material, while the data in the table were arranged according to the type of ion. Selected basic analytical parameters of the obtained electrodes have been collected and summarized in order to better illustrate and compare the achievements that have been described till now in this field of analytical chemistry, which is potentiometry. This comprehensive review is a compendium of knowledge in the research area of functional composite materials and state-of-the-art SC-ISE construction technologies.

This study presents a novel photoelectrochemical (PEC) conversion method for ion-selective electrodes (ISEs) based on CdS semiconductor film. The motivation stems from the need to enhance the sensitivity and precision of ISEs for various analytical applications. We synthesized CdS film on FTO conductive glass via a hydrothermal method and utilized this electrode as the working electrode. Under visible light irradiation, CdS generated photocurrent that is proportional to its applied voltage within a large potential window of ∼0.80 V. Ascorbic acid (AA) effectively inhibited electron-hole complexation, enhancing photocurrent stability. Potential modulation from ISEs acting as the reference electrode further regulated photocurrent generation, demonstrating excellent sensitivity and linearity for a wide range of ion concentrations. The method was validated by detecting serum calcium levels, showing agreement with traditional ISEs potentiometry and ICP-OES methods. This photoelectrochemical conversion strategy offers a promising approach for sensitive and accurate ion detection, with potential applications in clinical diagnostics and environmental monitoring. [Display omitted] • Synthesis of CdS film on FTO conductive glass via a hydrothermal method. • Utilization of a homemade Ca2+-ISE as the reference electrode. • Generation of photocurrent proportional to the bias voltage under visible light irradiation. • Demonstration of the effectiveness of ascorbic acid (AA) in enhancing photocurrent stability. • Regulation of photocurrent generation through varying ion concentration, resulting in excellent sensitivity and linearity. [ABSTRACT FROM AUTHOR]