Ion-selective Electrode Research Articles

Efficient Li+/Mg2+ separation by two-dimensional montmorillonite membrane with stable channel structure through ion exchange and metal–organic coordination strategy

Two-dimensional (2D) nanochannel membranes stacked by nanosheets are promising membrane separation materials. However, intrinsic swelling properties of 2D membrane have emerged as a significant challenge to establish stable nanochannels and achieve high separation performance. Inspired by the natural ion exchange property of montmorillonite (MMT), we constructed a two-dimensional MMT membrane with robust nanochannels by exchanging Fe3+ into interlayer of the membrane, and further achieved efficient separation of Li+/Mg2+ through coordination manipulation of tannic acid (TA) and Fe3+. Swelling was dramatically prevented by strong interlayer interaction between exchanged Fe3+ and nanosheets resulting in a 32-fold increase in anti-swelling properties. Furthermore, experiments and simulations revealed that TA could rapidly chelate with Fe3+ to form a dense hydrophilic functional layer on the membrane interface, which endowed MMT membranes with enhanced mechanical strength, cation transport and recognition, as well as anti-fouling properties. Consequently, the resulting MMT membranes showed the Li+/Mg2+ selectivity as high as 9.98 with a fast Li+ permeation rate (0.108 mol m-2h−1), which exceeded most of the previously reported membranes. This study proposed a novel strategy to diminish the trade-off effect among stability, ion flux, and selectivity of membranes, and inspired the development of next-generation ion selective separation membranes.

Solid Contact Microfabricated Electrode for Point-of-Care Electrochemical Determination of a Parasitic Infection Managing Medication Based on a Transducer Layer Prussian Blue Analogue Decorated with Multi-Walled Carbon Nanotubes

Point-of-care diagnostics (POC), often known as on-site testing has evolved as a quick and accurate methodology for analyzing and therapeutic monitoring of drugs. The aim of this study is to provide cost-effective, simple, portable, reliable, and ecofriendly methodology for determination of Tinidazole (TD); potentiometric sensors are found to be an ideal fit for achieving these goals. An advanced microfabricated ion selective electrode is provided employing two-steps procedure. The first is selecting the most selective ionophore for TD determination while the second is to improve the stability and detection limit upon doping the nanoparticles as ion to electron transducer layer between the microfabricated copper electrode and the ion selective media as it can decrease potential drift from 8.0 to ∼1.0 mV h−1. Nernstian potentiometric results were obtained for TD in range of concentration 1.0 × 10−3 to 1.0 × 10−8 M, its slope was −57.43 mV/decade with lower detection limits 2.55 × 10−9 M. Essential values of the adopted sensor are fast and stable response time (9 ± 2 s). The provided potentiometric approach succeeds to asses TD in its pure and pharmaceutical forms, furthermore in different biological fluids with satisfactory results.

Boosting lithium/magnesium separation performance of selective electrodialysis membranes regulated by enamine reaction

Monovalent cation exchange membranes (MCEMs) have progressively played an important role in the field of ion separation. However, according to transition state theory (TST), synchronously tuning the enthalpy barrier (△H) and entropy barrier (△S) for cation transport to improve ion separation performance is challenging. Here, the enamine reaction between the -NH- and -CHO groups is applied to regulate the subsequent Schiff-base reaction between the -CHO and -NH2 groups, which reduces the positive charges of the selective layer but increases the steric hindrance. The increased -T△S (△S term) for cation transport plays an important role in improving Li+/Mg2+ separation performance. The optimal positively-charged glutaraldehyde@piperazine/polyethyleneimine assembled membrane (M-Glu@PIP/PEI) has a perm-selectivity (Li+/Mg2+) of 31.83 with a Li+ flux of 1.87 mol·m-2·h-1, surpassing the Li+/Mg2+ separation performance of state-of-the-art monovalent ion selective membranes (MISMs). Most importantly, the selective electrodialysis (S-ED) process with M-Glu@PIP/PEI can be directly applied to treat simulated salt-lake brines (SLBs), and its superior Li+/Mg2+ separation performance and operational stability enables 74.44% of the lithium resources with a Li+ purity of 34.02% to be recovered. This study presents new insights into the design of high-performance MCEMs for energy-efficient resource recovery.

Highly stable and antifouling solid-contact ion-selective electrode for K+ detection in complex system based on multifunctional peptide and conductive MOF

Highly stable and antifouling solid-contact ion-selective electrode for K+ detection in complex system based on multifunctional peptide and conductive MOF

Surface functionalized porous MXene (Ti3C2Tx)/Polyethyleneimine membrane for efficient osmotic energy conversion

The development of ion-selective membranes is crucial for achieving efficient osmotic power conversion in reverse electrodialysis system. However, balancing ion selectivity and ion permeability in membranes remains a challenge, limiting improvements in energy conversion efficiency for practical applications. In this study, we develop efficient cation exchange membranes by integrating versatile aromatic hydroxyl groups with MXene nanosheets and polyethyleneimine (PEI) into their lamellar structure. This approach holds promise for achieving non-swelling, high selectivity, and enhanced power density for osmotic energy conversion. The abundance positive surface charge within PEI molecules, combined with the 2D sub-nanochannels of MXene nanosheets, facilitates the biomimetic replication of channel size, chemical groups, and adjustable charge density in the resulting membranes. The fabrication of these membranes is easily achieved through simple hydrothermal, functionalization, and surface-charged techniques, suggesting promising scalability. These membranes exhibit remarkable stability against swelling in aqueous solutions for up to 25 days and demonstrate a high selectivity of 0.95 and a superior output power density of 18.3 W/m2 in artificial river water and seawater.

Ion-selective electrode based on polyurethane-immobilized di-(2-ethyl hexyl) phosphoric acid for low-concentration aqueous Pb2+ detection and quantification

This study used a polyurethane (PU)-based ion selective electrode (ISE) immobilized with di-(2-ethyl hexyl) phosphoric acid (D2EHPA) to detect and quantify Pb2+ ions at low concentrations (10−10 to 10−1 M) in aqueous solution. PU, synthesized from castor oil (Ricinus communis L.), was utilized as the ISE membrane matrix. The ISE demonstrated a sensitivity of 26.24 ± 0.12 mV/decade, a detection limit of 1.44 × 10−7 M, and a response time of 10 s. We maintained the measurement stability for up to six days of storage.The results of Pb2+ quantification produced by ISE were compared with the results using atomic absorption spectroscopy (AAS), indicating similar Pb2+ concentrations in both artificial and real wastewater samples (calculated t-value < theoretical t-value). Therefore, this ISE is suitable for detecting trace levels of Pb2+ and quantifying them with high accuracy.

Tap water filtration and purification usage and their impact on the concentrations of fluoride and other minerals – A community-based study

ObjectiveThis 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. MethodsA 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. ResultsOne 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). ConclusionA 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 SignificanceUnderstanding 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.

All-solid-state K+ sensing array based on Au@polystyrene nanocomposites.

All-solid-state ion selective electrodes (ASS-ISEs) areeasy to miniaturize and array, meeting the needs of home sensing devices. However, ASS-ISEs still faces challenges in accuracy and stability due to basic potential changes caused by non-specific adsorption of charged background compositions and the complex electrode preparation steps. To this end, our group successfully subtracted the background signal by integrating a self-calibrating channel in the sensing array and simplified the electrode preparation steps by preparing multi-functional PS-Au nanocomposites. However, the uniformity and gold content of PS-Au nanocomposites are difficult to control, so Au@PS nanocomposites are prepared as sensor materials in this paper to further reduce the differences between batches of electrodes. K+ Au@PS sensing array can be obtained by directly dropping Au@PS nanocomposites on the screen-printed carbon electrodes (SPCEs), which shows a near Nernstian behavior in the range 1.0 × 10-3M to 0.3M and good reproducibility in real sample testing. The detection results by K+ Au@PS sensing array for K+ in human morning urine agreed well with that tested by ICP-AES, which make the K+-ASS-ISE suitable for home health monitoring.

Real-time and multiplexed detection of sodium and potassium ions using PEDOT:PSS OECT microarrays integrated with ion-selective membranes

In recent years, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT: PSS)-based organic electrochemical transistors (OECTs) have been intensively studied, and various applications have been explored, such as neural interfaces, cell electrophysiological recording and wearable electronics. Furthermore, PEDOT: PSS OECTs have gained attention for monitoring ion concentrations, such as sodium (Na+) and potassium (K+), across various fields, including environmental monitoring, clinical diagnostics, food quality control and even sweat monitoring. However, multiplexed sensing of such ions with high sensitivity and selectivity is still challenging. Therefore, this work presents a multiplexed sensing of ions with high sensitivity and selectivity utilizing PEDOT: PSS OECTs integrated with ion-selective membranes (ISMs). First, a microscale fabrication method for manufacturing OECT arrays based on PEDOT: PSS is described, and then the integration of Na+ and K+ISMs on OECT microarrays using the spin coating technique is introduced. A microfluidic cell was integrated with the OECTs for real-time measurement of Na+ and K+ ion concentrations in a controlled flow-through manner. Following this, the influence of the membrane composition and thickness on the sensing performance of the OECTs was statistically investigated. The OECTs displayed a consistent linear response towards the detected ion type in a concentration range from 1 to 100 mM, while exhibiting notable selectivity against the undesired ions. Our results indicate that a reduction in membrane composition and thickness leads to an increase in sensitivity, with the drawback of a decrease in selectivity for ion concentration detection. We optimized the ISMs for both ion types and utilized them on one and the same array for multiplexed monitoring of Na+ and K+ ion concentrations.

Phosphate Ion-Selective Electrode Based on Electrochemically Modified Iron.

The significance of the detection of phosphate ions is immense in the realms of chemistry, biology, medicine, environment, and industry. The detection of phosphate ions is currently mainly reliant on blue molybdenum colorimetry, which is accurate but requires sample pretreatment, intricate operation, and a high price tag. Consequently, it is essential to create a sensor with superior efficiency, precision, straightforward functioning, and instantaneous online detection. This study has designed and created an electrochemical modification based on an iron metal electrode for this purpose. Cyclic voltammetry was used to initially ascertain the potential (-0.57 V) necessary for constant potential electrolysis. Employing a constant potential electrolysis method, the iron oxide and its phosphate were modified onto the surface of the iron electrode to enable reaction with phosphate ions. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to characterize and analyze the morphology and elemental composition of Fe-PME, elucidating how it responds to phosphate ionation. The two-electrode system was then utilized for the evaluation of the phosphate ion response of Fe-PME at pH 4. Fe-PME's response to phosphate ions is demonstrated by the results, ranging from 10-5 to 0.1 M and with a slope of -52.8 mV dec-1. Fe-PME exhibited satisfactory results when compared to the conventional blue colorimetry of molybdenum.

Measuring insect osmoregulation in vitro: A reference guide

Osmoregulation is influenced by a wide variety of biotic and abiotic variables, and maintenance of systemic osmoregulatory homeostasis is critical to insect fitness. Because insects are so small, accurately quantifying renal organ function is technically challenging, and often requires specialized equipment. On top of this, nearly a century of toiling in the laboratory has led to a wide and still growing variety of methods that can be difficult for novice researchers to disentangle. Here, we provide a reference guide for the most used in vitro approaches in the study of insect osmoregulation, including the Ramsay assay, Ussing chamber, epithelial potential measurement, scanning ion-selective electrode technique, and hindgut assays. Along the way, we highlight the history of each methodological innovation.

A Novel Sulfonated Polyimide Composite Membrane Containing a Sulfonated Porous Material for All-Vanadium Redox Flow Batteries.

To improve the battery efficiency and cycling stability of sulfonated polyimide (SPI), a polyphosphazene with built-in -SO3H moieties (PP-SO3H), which is a porous covalent organic framework (COF) material, is facilely synthesized by the polymeric combination of hexachlorocyclotriphosphazene (HCCP) and p-diaminobenzenesulfonic acid. Due to its tunable pore size and flexible molecular design, the COF material can address the trade-off between the conductivity and the ion permeability of ion exchange membranes well, thereby improving the ion selectivity of membranes. The experimental results show that the SPI/PP-SO3H composite membrane has an excellent conductivity (up to 114.8 mS cm-1); the ion selectivity of the SPI/2% PP-SO3H membrane is 11.69 × 104 S min cm-3, which is 2.18 times higher than that of the SPI base membrane. PP-SO3H also improves the SPI membrane's mechanical strength, and the effect of PP-SO3H on SPI intermolecular interactions is analyzed by surface electrostatic potential (ESP) theoretical calculations. The Coulombic efficiency (CE) of the SPI/2% PP-SO3H membrane is 98.92%, the energy efficiency (EE) is 84.1% at a current density of 100 mA cm-2, and the self-discharge time of the SPI/2% PP-SO3H membrane is 3.5 times compared with the SPI base membrane. To measure the cycling stability of the composite membrane, the SPI/2% PP-SO3H membrane is cycled in the VRFB for more than 400 cycles, which is more stable than that of the SPI base membrane. These results show that SPI/2% PP-SO3H composite membranes are viable for VRFB applications.

Influences of marine biofouling on the potential responses of polymeric membrane ion-selective electrodes

Using polymeric membrane ion-selective electrodes (ISEs) for reliable long-term marine environmental observations is still a challenge due to the formation of biofilms on electrode surfaces. Unfortunately, the contributions of the specific biofilm components to sensor failure have not been studied. Herein, the influences of the specific biofilm components on the performance of the neutral carrier-based polymeric membrane ISEs are systematically investigated in terms of sensitivity, selectivity, and stability. More importantly, the spatial distributions of these foulants in the fouled sensing membrane phase are studied by confocal laser scanning microscopy for the first time to give insight into the fouling mechanisms. Three typical biochemicals (i.e., proteins, polysaccharides, microbial lipids) in biofilms are selected as the representative foulants. The poly (vinyl chloride)-based CO32--ISEs and K+-ISEs/Ca2+-ISEs have been selected as the model sensors for detection of anions and cations, respectively. Experiments show that depending on the type of the biofoulants, the adsorption of the foulants on the polymeric membrane surface and/or their extraction into the organic membrane phase could occur and induce a change in the potential responses. This study provides a deep insight into the influences of the specific biofilm components on the polymeric membrane ISEs, which is of importance for development of the polymeric membrane marine sensors with high antifouling capabilities for long-term marine monitoring.

High-Performance Electrochemical Creatinine Sensors Based on β-Lead Dioxide/Single-Walled Carbon Nanotube Electrodes.

Creatinine is an important biomarker of kidney function and muscular metabolism. In this paper, we developed the β-lead dioxide/single-walled carbon nanotube (β-PbO2/CNT) and the β-PbO2/CNT ion-selective electrode (β-PbO2/CNT/ISE), which were used as highly sensitive potentiometric sensors for creatinine detection. The fabricated electrodes exhibited highly pH-sensitive characteristics due to the synergistic effect of the electrochemical properties of CNT and β-PbO2. Moreover, an ammonium-ion-selective membrane coating allowed the β-PbO2/CNT electrode to be NH4+-selective for direct detection of the ammonium ion. By exploiting the electrochemical characteristics of these electrodes, the creatinine assay was established through the one-step selective conversion of creatinine by creatinine deiminase, in which the OH- and NH4+ generated by the enzymatic reaction were detected using β-PbO2/CNT and β-PbO2/CNT/ISE electrodes as pH- and NH4+-responsive sensors, respectively. The total creatinine assay can be completed within ∼5 min. The assay results from β-PbO2/CNT and β-PbO2/CNT/ISE showed excellent sensitivity values of -75.56 and 64.62 mV in the detection range of 10-400 μM with a fast response (20 s), and the limits of detection were calculated to be 0.06 and 0.13 μM, respectively. Moreover, the developed creatinine sensor showed high selectivity against 11 interfering bio/chemical species with negligible interferences (selectivity coefficient <10-4) and excellent repeatability (>97% within 25 cycles) and long-term stability for 4 weeks of storage. In addition, the feasibility and practicality of the device were successfully demonstrated in human serum tests, with recoveries of 95-104% for PbO2/CNT and 92-110% for PbO2/CNT/ISE.

Insights into solid-contact ion-selective electrodes based on laser-induced graphene: Key performance parameters for long-term and continuous measurements.

This work aims to serve as a comprehensive guide to properly characterize solid-contact ion-selective electrodes (SC-ISEs) for long-term use as they advance toward calibration-free sensors. The lack of well-defined SC-ISE performance criteria limits the ability to compare results and track progress in the field. Laser-induced graphene (LIG) is a rapid and scalable method that, by adjusting the CO2 laser parameters, can create LIG substrates with tunable surface properties, including wettability, surface chemistry, and morphology. Herein, we fabricate laser-induced graphene (LIG) solid-contact electrodes using different laser settings and subsequently convert them into ion-selective sensors using a potassium-selective membrane. We measure the aforementioned tunable surface properties and correlate them with resultant low-frequency capacitance and water layer formation in an effort to pinpoint their effects on the sensitivity (Nernstian response), reproducibility (E°' variation), and potential stability of the LIG-based SC-ISEs. More specifically, we demonstrate that the surface wettability of the LIG substrate, which can be tuned by controlling the lasing parameters, can be modified to exhibit hydrophobic (contact angle > 90°) and even highly hydrophobic surfaces (contact angle ≈ 130°) to help reduce sensor drift. Recommendations are also provided to ensure proper and robust characterization of SC-ISEs for long-term and continuous measurements. Ultimately, we believe that a comprehensive understanding of the correlation between LIG tunable surface properties and SC-ISE performance can be used to improve the electrochemical behavior and stability of SC-ISEs designed with a wide range of materials beyond LIG.

Lab-on-a-chip paper-based electrochemically assisted solid-phase microextraction and ion selective sensor for determination of naproxen in biological fluid samples

BackgroundThe integration of paper-based analytical devices with lab-on-a-chip technology has opened up new possibilities for miniaturized, rapid, low cost and portable diagnostic testing in resource limited settings. This work introduces an integrated lab-on-a-chip platform coupling paper-based analytical devices (LOC-PADs) for dual usage: electrochemically controlled solid-phase microextraction (EC-SPME) and determination of naproxen (NAP) by potentiometric ion-selective electrode (ISE) in biological samples. ResultsConductive papers were successfully fabricated by a chemical procedure. Thereupon, a conducting molecularly imprinted polymer (CMIP) film based on PPy and an anionic model drug (NAP) as a template were applied to the conductive paper substrate via electrochemical methods. A microfluidic chip device was employed to assess the analytical performance of the fabricated paper-based CMIP. The designed chip is divided into two parts with a microfluidic channel between them. The first chamber is an extraction zone for EC-SPME of NAP by using the CMIP paper as a selective sorbent. The second chamber is the detection zone and consists of a paper-based NAP ion selective sensor for potentiometric detection of drug. The analytical process was investigated and optimized for each chamber. Remarkable selectivity towards NAP was achieved in the concentration range from 4.0 × 10−7 to 1.0 × 10−2 mol L−1 with determination coefficient (R2 = 0.99) and the limit of detection (LOD) was 2.0 × 10−7 mol L−1. Anionic Nernstian compliance was gained −58.5 ± 0.5 mV decade−1, and response time in the detection step was 7s for ISE. Satisfactory spiking recovery values within the acceptable range of 90–110 % with RSDs ≤7 % were achieved for the analysis of real samples with fully portable LOC device. SignificanceThe LOC-PADs were favorably used for selective extraction and determination of NAP in serum and saliva samples, respectively. EC-SPME caused sample clean-up, reduced or eliminated different interferences and enhanced selective response of ISE as detection zone of device. Integration of EC-SPME and ISE in a single chip enabled easy and fast determination of trace amounts of NAP in limited real sample volumes, and fully portable advantages.

A cutting edge potentiometric determination of baricitinib in synthetic wastewater and in tablet dosage form using modified carbon paste ion-selective membrane

After the recent hit of COVID-19, many drugs were successively administered to save patients’ lives and those drugs reached aquatic sources, one of those drugs was Baricitinib. Driven by the current situation, a potentiometric technique using an ion-selective membrane (ISM) recipe drop cast on a modified carbon paste electrode was optimized for the superior determination of Baricitinib (BAR). The molecular docking was customized to optimize the proper ionophores incorporated in the ISM, revealing that beta-cyclodextrin (β-CD) is the most compatible ionophore with the studied drug. A multivariate optimization experimental design was employed to optimize the best experimental condition for the analytical method. To this end; dual nanoparticles (multi-walled carbon nanotubes and copper oxide nanoparticles) were incorporated in the carbon paste electrode, and the ISM recipe was enriched with β-CD and cation-exchanger (phosphotungstic acid) in a polyvinylchloride matrix plasticized with dibutyl phthalate. A Nernstian slope equal to 19.97 mV/decade with a linearity range of 7.99 × 10−7–1.00 × 10−3 M was obtained. The validated sensor exhibited good recovery when used to determine the studied drug in synthetic wastewater and tablet dosage form. The greenness of the method was evaluated using the Complementary Green Analytical Procedure Index and Blue Applicability Grade Index.

Visualization of water and ion transport in ion-selective membranes

An approach allowing visualization of processes occurring during pretreatment of ion-selective membranes is proposed. This method does not interfere with potentiometric performance of sensors, thus it can be used to follow pretreatment of sensors intended for electrochemical studies. The approach uses neutral dye Nile red added to the membrane in minute amounts. Due to unique properties of the dye, water partition to the membrane can be monitored as decrease of emission characteristic for the dye dispersed in the lipophilic phase (plasticizer) and formation of a new emission peak at longer wavelengths. The latter is characteristic for Nile red present in the aqueous phase dispersed in the lipophilic liquid, its formation is related to dye interactions with cation exchanger. Visually this process can be observed as change in the cation selective membrane color from red to violet. This process is reversible – drying of the membrane or incorporation of primary ions to the phase results in increase of the emission at wavelength characteristic for Nile red dispersed in the plasticizer phase, and change of the membrane color back to red. Thus, the proposed approach allows insight into the membrane pretreatment process: equilibration with water, drying or incorporation of ions and ultimately results in better control of this process.

3D-Printed Transducers for Solid Contact Potentiometric Ion Sensors: Improving Reproducibility by Fabrication Automation.

3D printing technology has become attractive in the development of electrochemical sensors as it offers automation in fabrication, customization on-demand, and reproducibility, among other features. Nonetheless, to date, solid contact potentiometric ion sensors have remained overlooked using this technology. Thus, the novelty of this work relies on demonstrating for the first time the usefulness of the multimaterial 3D printing approach to manufacture potentiometric ion-selective electrodes. The significance is indeed twofold. First, we discovered that by using the polyethylene terephthalate glycol (PETg) and polylactic acid-carbon black (PLA-CB) filaments together with a rational electrode design containing a well to accommodate the ion-selective membrane, a tight seal among all of the sensing materials is obtained. Importantly, this has mainly impacted the electrode-to-electrode reproducibility (ERSD0 ± 3 mV). Second, 75 ready-to-use electrodes can be printed in less than 3.5 h in a completely automated manner at a cost of ∼0.32 €/sensor. This feature may positively impact the suitability of further scaled-up production as well as the possibility of application in low-resource contexts. Overall, the presented outcomes are expected to encourage certain research directions to adopt using multimaterial 3D-printing approaches for producing highly reproducible solid contact potentiometric ion-selective electrodes, but are not restricted to them.

Novel usage of perinone polymer as solid contact in ion-selective electrodes

The paper presents the use of a new perinone polymer (PPer) as an intermediate layer and the development of a new type of potassium ion-selective electrodes with solid contact. The PPer layer was applied to the surface of a glassy carbon electrode using potentiodynamic polymerization from an electrolyte solution containing perinone precursors (Per). Subsequently, the surface of the electrode after application of the polymer was examined using a microscope and an optical profilometer. To check the quality of the prepared ion-selective electrodes, a series of tests were carried out and the analytical and electrical parameters of the electrodes were determined. Electrode modifications using PPer improved the electrode parameters, especially the stability and reversibility of the potential, compared to the control electrode covered only with an ion-sensitive membrane. The best electrode was the electrode modified with PPer applied in 10 cycles, which, as a result of the modification, allowed better parameters to be obtained – slope 58.86 mV/decade, LOD 1.2 × 10−6 M, linearity range 5 × 10−6 – 1 × 10−1 M. A very low short-term potential drift value of 2.7 × 10−4 mV/s was obtained as well as an extremely satisfactory SD value of 1.1 mV from E0 measurements. The modification also improved electrical properties and gave a negative result of the water layer test.