Search Results (79)

A strong application potential for Ag/AgCl ion-selective electrodes (ISEs) used as chloride sensors in cement-based material is widely accepted, but their stability and durability have not been sufficiently addressed. This paper summarizes the research status of the stability and durability of Ag/AgCl ISEs used for the non-destructive detection of chloride in cement-based materials. Four topics including working principle and fabrication methods, the factors that influence stability, research status for stability and durability studies, and the reason for durability failure of Ag/AgCl ISEs in cement-based materials are reviewed. Meanwhile, the improving methods for Ag/AgCl ISEs are proposed based on discussions of various aspects of Ag/AgCl ISEs. Full article

This study focused on the development of Na⁺ ion sensing devices on a flexible substrate and investigated the impact of various additive materials on its sensing performance. For the Na⁺ ion sensing aspect, the film on the carbon working electrode used tert-butyl calix[4]arene tetraethyl acetate as the ion carrier. The main component of the film was polyvinyl chloride (PVC), with a plasticizer added to enhance its flexibility, ensuring better adaptation to the flexible substrate. In this base formulation, graphene oxide (GO) or multi-walled carbon nanotubes (MWCNTs) were incorporated into the sensing electrode to explore their effects on Na⁺ ion sensing capabilities. The results demonstrated that adding MWCNTs significantly improved the sensor’s sensitivity to Na⁺ ions. In addition, the study used the response slope to Na⁺ ions as a comparative reference for selectivity by calculating the ratio of the Na⁺ ion response slope to the response slopes of other ions (such as K⁺ and Ca²⁺). The findings showed that the sensors with MWCNTs exhibited better selectivity than the others with GO, and therefore, further analysis was performed on the response time of the sensors with MWCNTs. The results indicated that incorporating MWCNTs reduced the sensors’ response time and enhanced their overall sensitivity. However, excessive addition of MWCNTs would lead to a decrease in the selectivity of the fabricated sensors. This suggests that while MWCNTs offer promising improvements in performance, their concentration must be carefully optimized to maintain the sensors’ selectivity. Full article

A simple and easily applicable analytical method for the simultaneous determination of Cd²⁺, Pb²⁺, Zn²⁺, Cu^2+, and Cl⁻ by applying a modified carbon paste electrode with saffron-conjugated silver nanoparticles (AgNPs@Sa) is being presented. The modified CPE was then used for the simultaneous determination of Cd²⁺, Pb²⁺, Zn²⁺, and Cu²⁺ as well as chloride ions in soil and plants. The comparative analysis demonstrated a significant enhancement in the applicability of the modified electrode through the incorporation of silver nanoparticles (AgNPs) at the carbon paste electrode (CPE) surface, leading to the development of a poly-Sa-CPE. This newly proposed method offers notably superior qualitative performance compared to other metal nanoparticle-based modifications reported in the literature. The accordingly modified electrode was successfully applied in the development of a chloride ion. A novel sensor is being proposed that makes possible the determination of heavy metals and chlorides in the same solution, in soil and plant samples. The enhanced sensitivity and selectivity of the poly-Sa-CPE system highlights its potential as a more effective alternative for heavy metal and chloride analysis, further demonstrating its advantages in electrochemical applications. The LODs of Cd²⁺, Pb²⁺, Zn^2+, Cu²⁺, and Cl⁻ for their simultaneous determination are 0.38 μg·L⁻¹, 0.44 μg·L⁻¹, 0.72 μg·L⁻¹, 0.42 μg·L⁻¹, and 0.11 μg·L⁻¹, respectively, with comparably high relative standard deviations of about 8.1%, 9.4%, 8.3%, 7.6%, and 7.9%, respectively. Full article

This study focused on developing a novel composite phosphate-selective electrode for on-site and real-time applications using a silver polyglutaraldehyde phosphate and carbon nanotube (CNT) matrix. CNT-silver polyglutaraldehyde phosphate compound was synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The potentiometric performance of the composite phosphate-selective electrode was then investigated. The results demonstrated that the composite phosphate-selective electrode exhibited good sensitivity, with a linear response in the concentration range of 1.0 × 10⁻⁴ to 1.0 × 10⁻² M for phosphate ions. The electrode also showed high selectivity towards phosphate ions compared to other anions, such as chloride and nitrate. Additionally, the electrode displayed a quick response time of less than 15 s, making it suitable for real-time measurements. The electrode was applied to surface and soil water samples. The results obtained from the water samples showed a strong correlation with those obtained from the preferred spectrophotometry method, highlighting the potential of the developed electrode for on-site and continuous monitoring of phosphate and offering an efficient and practical solution for various fields that require phosphate detection. Full article

The application of membrane sensors for the detection and quantification of pharmaceutical environmental contaminants has become a significant goal in recent years. Due to the widespread application of levofloxacin hemihydrate (LEVO) in medicine, its occurrence in the environment, especially in surface water bodies like rivers, is quite likely. Extended exposure of river water to sunlight and the photo-degradability of LEVO may facilitate its photo-degradation. To measure LEVO in the presence of its principal photo-degradants, two sensitive and selective membrane electrodes were designed. A polyvinyl chloride electrode (PVCE) and a screen-printed electrode (SPE) were constructed for the selective analysis of the investigated drug. Phosphomolybdic acid was used to prepare a lipophilic ion pair with the studied drug. All test parameters were optimized to achieve the best electrochemical performance. The electrodes demonstrated a linear range from 1 × 10⁻⁶ M to 1 × 10⁻² M. The PVCE and SPE demonstrated slopes of 55.80 ± 0.70 mV/decade and 56.90 ± 0.50 mV/decade, respectively. The aforementioned sensors demonstrated satisfactory performance within a pH range of 3.0 to 5.0. The fabricated sensors were successfully utilized to accurately quantify LEVO in the presence of its primary photo-degradants. The membranes were effectively utilized to measure LEVO in river water samples without requiring pre-treatment processes. Full article

A nitrate selective electrode was used for real-time in situ potentiometric monitoring of a batch nitrate removal process using activated carbon and ion exchange resin. A plasticized polymeric membrane consisting of polyvinyl chloride, 2-nitrophenyl octyl ether and tridodecyl methyl ammonium chloride was incorporated into an ion-selective electrode body. First, the dynamic potential response of the electrode to nitrate was investigated. Two commercial activated carbons with different physical properties were then tested. Nitrate removal with these carbons was monitored potentiometrically using several nitrate concentrations. The extreme turbidity of the solutions was not a drawback during potentiometric monitoring of the process, which is a clear advantage over other methods such as optical monitoring. The potential versus time recordings were converted into nitrate concentration versus time plots, which were evaluated with different adsorption kinetic models. A pseudo-second order kinetic model for nitrate adsorption on both activated carbons was found to fit the experimental data very well. The values of the kinetic parameters were very different between the two activated carbons. The proposed methodology was also satisfactorily applied to the study of nitrate removal by an ion exchange resin. In this case, the experimental results clearly follow a pseudo-first order kinetic model. Potential applications of the proposed methodology for monitoring nitrate removal in real water samples are discussed. Full article

Urine is an organic fluid produced by the kidney, and its analysis is one of the most requested laboratory tests by clinicians. The ionic composition of urine has been shown to be a good health indicator: it is useful for the diagnosis of several diseases, as well as monitoring therapeutics. This review considers laboratorial techniques that have been used throughout time for the quantification of ions in urine, and also considers some methodologies that can potentially be used in clinical laboratories for this kind of analysis. Those methods include gravimetry, titration, flame emission spectrophotometry (flame photometry), fluorimetry, potentiometry (ion selective electrodes), ion chromatography, electrophoresis, kinetic colorimetric tests, enzymatic colorimetric tests, flow cytometry, atomic absorption, plasma atomic emission spectrometry, and paper-based devices. Sodium, potassium, chloride, calcium, and magnesium are among the most important physiological ions, and their determination is frequently requested in hospitals. There have been many advances regarding the analysis of these ions in 24 h urine. However, there is still some way to go concerning the importance of intracellular ions in this type of sample as well as the use of occasional urine for monitoring these parameters. Full article

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. Full article

Electrochemical (EC) detection is a powerful tool supporting simple, low-cost, and rapid analysis. Although screen printing is commonly used to mass fabricate disposable EC chips, its mask is relatively expensive. In this research, we demonstrated a method for fabricating three-electrode EC chips using 3D printing of relatively high-viscosity paste. The electrodes consisted of two layers, with carbon paste printed over silver/silver chloride paste, and the printed EC chips were baked at 70 °C for 1 h. Engineering challenges such as bulging of the tubing, clogging of the nozzle, dripping, and local accumulation of paste were solved by material selection for the tube and nozzle, and process optimization in 3D printing. The EC chips demonstrated good reversibility in redox reactions through cyclic voltammetry tests, and reliably detected heavy metal ions Pb(II) and Cd(II) in solutions using differential pulse anodic stripping voltammetry measurements. The results indicate that by optimizing the 3D printing of paste, EC chips can be obtained by maskless and flexible 3D printing techniques in lieu of screen printing. Full article

A composite solid chloride sensor consisting of two single sensors, i.e., Ag/AgCl working electrode and Mn/MnO₂ reference electrode, was developed. The Ag/AgCl electrode was prepared by the anodic polarization method, while the Mn/MnO₂ reference electrode was prepared using the powder compaction technique. Then, the electrochemical performances such as stability, reproducibility, and sensitivity of the composite and single sensors were investigated in a saturated Ca(OH)₂ solution and mortar specimen. A current density of 0.5 mA/cm² and polarization time of 2.5 h were the optimal preparation parameters of the Ag/AgCl selective electrode. The Ag/AgCl selective electrode showed a linear potential response with the logarithm of chloride ion content in solution and had good stability, reproducibility, and anti-polarization performances. In addition, the Mn/MnO₂ electrode exhibited potential stability after being activated in an alkaline solution for 60 days. The composite sensor demonstrated exceptional sensitivity to the Cl⁻ content, boasting a slope of approximately 51.1 mV/decade, and showcased excellent stability in both solution and mortar specimens. In every measurement, the time needed for the potential of a composite sensor to become stable was less than 30 s. The sensor enables non-destructive in situ monitoring of the chloride ion content in cement mortar, thus realizing early warning of deterioration of reinforcement and guaranteeing long service life of the structure. Full article

Cost-effective bismuth (Bi) boasts a high theoretical capacity and exceptional selectivity towards Cl^- ion storage, making it a promising material for desalination batteries (DBs). However, the substantial volume expansion and low conductivity severely hinder the cycling performance of Bi-based DBs. In this study, a carbon-layer-coated Bi nanocomposite (Bi@C) was synthesized by pyrolyzing a metal–organic framework (Bi-MOF) containing Bi using a straightforward method. The results show that the Bi@C synthesized under the condition of annealing at 700 °C for 2 h has the optimum properties. The Bi@C has good multiplication performance, and the desalination capacity is 106.1 mg/g at a high current density of 1000 mA/g. And the material exhibited a high desalination capacity of 141.9 mg/g at a current density of 500 mA/g and retained 66.9% of its capacity after 200 cycles. In addition, the Bi@C can operate at a wide range of NaCl concentrations from 0.05 to 2 mol/L. The desalination mechanism analysis of the Bi@C revealed that the carbon coating provides space for Bi particles to expand in volume, thereby mitigating the issues of electrode material powdering and shedding. Meanwhile, the porous carbon skeleton establishes electron and ion channels to enhance the electrode material’s conductivity. This research offers a promising strategy for the application of chloride-storage electrode materials in electrochemical desalination systems. Full article

The results of this research on the electrochemical behavior of Cu24Zn5Al alloy in a 0.1 mol/dm³ sodium sulfate (Na₂SO₄) solution containing 1-phenyl-5-mercaptotetrazole (PMT) are presented in this paper. The influence of PMT concentration, chloride ion concentration, and pre-treatment were examined. The influence of pre-treatment was studied in terms of the effect of the immersion time of the electrode in the appropriate inhibitor solution. After selecting the optimal immersion time, its effect on the behavior of the Cu24Zn5Al alloy was tested in a 0.1 mol/dm³ solution of sodium sulfate in the presence of different concentrations of chloride ions. Research shown that with the increase of PMT concentration, the anodic current density around the corrosion potential decreases, indicating that PMT behaves as a corrosion inhibitor for Cu24Zn5Al alloy. Full article

The monitoring of potassium ion (K⁺) levels in human sweat can provide valuable insights into electrolyte balance and muscle fatigue non-invasively. However, existing laboratory techniques for sweat testing are complex, while wearable sensors face limitations like drift, fouling and interference from ions such as Na⁺. This work develops printed electrodes using β-cyclodextrin functionalized reduced graphene oxide (β-CD-RGO) for selective K⁺ quantification in sweat. The β-CD prevents the aggregation of RGO sheets while also providing selective binding sites for K⁺ capture. Electrodes were fabricated by screen printing the β-CD-RGO ink onto conductive carbon substrates. Material characterization confirmed the successful functionalization of RGO with β-CD. Cyclic voltammetry (CV) showed enhanced electrochemical behavior for β-CD-RGO-printed electrodes compared with bare carbon and RGO. Sensor optimization resulted in a formulation with 30% β-CD-RGO loading. The printed electrodes were drop-casted with an ion-selective polyvinyl chloride (PVC) membrane. A linear range from 10 μM to 100 mM was obtained along with a sensitivity of 54.7 mV/decade. The sensor showed good reproducibility over 10 cycles in 10 mM KCl. Minimal interference from 100 mM Na⁺ and other common sweat constituents validated the sensor’s selectivity. On-body trials were performed by mounting the printed electrodes on human subjects during exercise. The K⁺ levels measured in sweat were found to correlate well with serum analysis, demonstrating the sensor’s ability for non-invasive electrolyte monitoring. Overall, the facile synthesis of stable β-CD-RGO inks enables the scalable fabrication of wearable sensors for sweat potassium detection. Full article

A heterocyclic compound of S and N with cyclic structures, like Furans, thiophenes and related azole analogs, is important as a ligand because of it is readily available, stable and easily functionalized. Various types of heterocyclic molecules quinazolines and their derivatives contain important chromophores with desirable electrochemical properties to be applied in the sensor field. Metal complexes of these compounds have demonstrated significant electrochemical properties as ionophore or electroactive materials for the fabrication of ISEs with different polymeric membranes. R. Selva Kumar et al. 2019 reported the use of dibutyl(8-hydroxyquinolin-2-yl)methylphosphonate as ionophore in a PVC matrix for the fabrication of a potentiometric thorium(IV) ion-selective electrode These quinazoline-based membranes with other additives and plasticizers are very useful for the development of a potential difference across the membrane at membrane-solution interface in the required proportions . Analytes, such as Butralin, Hydroxylamine, and Nitrite, and heavy metal ions, like Fe³⁺ and Th⁴⁺, have also been determined using quinazoline-based membrane sensors. ISE-based electrochemical sensors are very useful in the analysis of food products, drinking water, beverages, fertilizers, soil industrial effluents, etc. They also are applied in potentiometric titration as indicator electrodes. Full article

The entrance of even a small amount of phosphorus compounds into natural waters leads to global problems that require the use of modern purification technologies. This paper presents the results of testing a hybrid electrobaromembrane (EBM) method for the selective separation of Cl⁻ (always present in phosphorus-containing waters) and H₂PO₄⁻ anions. Separated ions of the same charge sign move in an electric field through the pores of a nanoporous membrane to the corresponding electrode, while a commensurate counter-convective flow in the pores is created by a pressure drop across the membrane. It has been shown that EBM technology provides high fluxes of ions being separated across the membrane as well as a high selectivity coefficient compared to other membrane methods. During the processing of solution containing 0.05 M NaCl and 0.05 M NaH₂PO₄, the flux of phosphates through a track-etched membrane can reach 0.29 mol/(m²×h). Another possibility for separation is the EBM extraction of chlorides from the solution. Its flux can reach 0.40 mol/(m²×h) through the track-etched membrane and 0.33 mol/(m²×h) through a porous aluminum membrane. The separation efficiency can be very high by using both the porous anodic alumina membrane with positive fixed charges and the track-etched membrane with negative fixed charges due to the possibility of directing the fluxes of separated ions in opposite sides. Full article