Selective Electrode Research Articles

Visualizing the Effect of Temperature on Carbonate Salt Production in CO2 Electrolysis

Carbon dioxide (CO2) electrolysis is a novel and promising technology to tackle anthropogenic climate change by reducing our dependency on fossil fuels and creating a sustainable carbon cycle. However, current CO2 electrolysis suffers from low CO2 reduction reaction (CO2RR) selectivity and rapid gas diffusion electrode (GDE) degradation and flooding due to carbonate precipitation. As the hydrophilic precipitate accumulates in the porous structure of the cathode GDE, the liquid anolyte invades the pores, blocking the catholyte from reaching the catalyst layer. This effect promotes the adverse hydrogen evolution reaction and thus decreases the CO2RR selectivity (1). Current literature focuses on limiting carbonate precipitate formation as opposed to understanding the factors affecting its growth (2). While carbonate precipitation is dependent on the specific electrolyte in a flow cell, the impact of parameters, such as operating temperature and GDE porosity, on the nature of carbonate precipitation still need to be investigated (3).In this study, we examine the relationship between cell temperature with carbonate precipitate accumulation. A zero-gap alkaline membrane electrode assembly (MEA) was used with potassium carbonate as the anolyte and humidified CO2 as the catholyte. Electrochemical impedance spectroscopy was used to calculate the activation, ohmic, and mass transport losses of the cell before and after a constant current density phase where faradaic efficiency was measured to quantify the CO2RR selectivity degradation due to salt accumulation. Furthermore, to characterize precipitate growth, the cathode GDEs were imaged before and after electrochemical testing using scanning electron microscopy (SEM) and wavelength dispersive spectroscopy (WDS). To quantify precipitate-driven flooding over operation time, identical MEAs were imaged using operando X-ray synchrotron radiography over a range of temperatures. Through-plane images of the operating cell were processed to find the electrolyte thickness in the cathode GDE as a function of time. Radiography results revealed progressive, cyclical flooding as well as preferential gas pathways. Moreover, after four hours of constant current operation and at a cell temperature of 60℃, the catalyst layer exhibited large amounts of uniformly distributed precipitates, while the GDE contained large, localized precipitate crystals. This indicates that at high temperatures, carbonate precipitates significantly block the catalyst layer and cause flooding into the substrate layer. This work provides new insight into the effect of temperature on carbonate precipitate buildup, deepening the understanding of the mechanism responsible for precipitate degradation. M. E. Leonard, L. E. Clarke, A. Forner-Cuenca, S. M. Brown, and F. R. Brushett, ChemSusChem, 13 (2020).Y. Xu et al., ACS Energy Lett, 6, 809–815 (2021).E. R. Cofell, U. O. Nwabara, S. S. Bhargava, D. E. Henckel, and P. J. A. Kenis, ACS Appl Mater Interfaces, 13, 15132–15142 (2021).

Investigating Enzyme-Based Electrode Processes Using Electrochemical Impedance Spectroscopy and Distribution of Relaxation Time Analysis

Enzymatic fuel cells (EFCs) are an emerging class of electrochemical devices that have the potential to harness renewable energy sources by converting the chemical energy of an organic substrate into electrical energy. Enzymes are responsible in an EFC for highly selective and efficient electrode processes under typically mild ambient conditions, such as the oxidation reaction at the anode and the reduction reaction at the cathode 1. In addition to more conventional techniques, electrochemical impedance spectroscopy (EIS) can be employed to characterize such systems. Electrochemical behavior of enzymatic electrodes, such as enzyme reaction kinetics, substrate mass transport, and electrode stability, can be studied by measuring the system's impedance over a wide frequency range and then performing a precise post-process analysis based on the distribution of relaxation time (DRT). DRT analysis is rarely used to interpret EIS spectra within the EFCs research field, despite the fact that it is widely acknowledged as relevant for properly understanding the EIS potential to improve power density in fuel cells 2,3. Glucose oxidase (GOx) and bilirubin oxidase (BOD) were immobilized on multi-walled carbon nanotubes (MWCNTs) to catalyze the bioelectrocatalytic oxidation of glucose at the anode and the bioelectrocatalytic reduction of oxygen at the cathode, respectively. This study presents a promising approach for the investigation of enzyme-based anodic and cathodic processes by measuring them with EIS and then interpreting the results with DRT analysis, as depicted in Figure 1. By varying different operating parameters, such as the enzymatic loading on the electrode surface or electrolyte conditions, this method can be used to identify three primary relaxation processes occurring at both electrodes. At the interface between the electrolyte and the electrode, it is possible to conclude that high-frequency processes are accountable for ionic conduction, intermediate-frequency processes are accountable for charge transfer, and low-frequency processes are accountable for oxygen surface exchange and diffusion.This method provides access to preliminary fundamental information about enzymatic bioelectrode processes, which can be used to optimize biofuel cell construction and compositions and increase their power output. Figure 1. Schematic representation of the characterization method used to characterize a GOx-CNT-modified anode consisting of EIS measurements and subsequent DRT analysis. Concentration of glucose 175 mM in 0.1 M HEPES Buffer, pH 7; EIS parameters: 20 mV sinusoidal excitation, 0.1 Hz-100 kHz. References K. Herkendell, A. Stemmer and R. Tel-Vered, Nano Res., 12(4), 767–775 (2019). H. Wang, X. Long, Y. Sun, D. Wang, Z. Wang, H. Meng, C. Jiang, W. Dong and N. Lu, Frontiers in microbiology, 13, 973501 (2022). F. Ciucci, Current Opinion in Electrochemistry, 13, 132–139 (2019). Figure 1

(Digital Presentation) Construction of a Novel Phosphate Potential Sensor and Its Application

Phosphorus content is one of important indicators in the evaluation of water quality. The level of phosphorus in oilfield water systems not only affects the overall water cycle production system, but excessive phosphorus wastewater entering the environment can cause eutrophication of the water body, as can high levels of ammonia and nitrogen, and leading to rapid growth of algae and thus affecting the balance of the aquatic ecosystem. Therefore, the regulation of phosphorus is of great importance. Phosphorus exists in nature mainly in the form of phosphate, which is currently detected by the traditional spectrophotometric method. As this method requires the addition of a large number of chemical reagents, it is not only complex and time consuming, but also produces a waste solution at the end of the test that can easily cause secondary pollution to the environment. Compared to traditional methods, Ion Selective Electrodes (ISEs) are easier to use, more sensitive, less expensive and do not cause secondary contamination. In conventional ion selective electrode detection systems, liquid contact ion selective electrodes consisting of a polymeric ion selective membrane, an internal filling fluid and an internal reference electrode are susceptible to common variables such as pressure and temperature. There are problems with complex maintenance, leakage and signal calibration. In contrast, all-solid ion-selective electrodes that eliminate the internal filling fluid and internal reference have become a hot research topic for such potential-based sensors. In this thesis, the following research was carried out with the aim of developing a phosphate potentiometric sensor with practical detection capabilities:(1) PANI/ITO electrodes were produced by electrodeposition of polyaniline on ITO conductive glass by constant potential deposition and by ultrasonic peeling. Three oxidation states of PANI/ITO electrodes were prepared at different voltages using phosphoric acid as the doping solution. LBPANI/ITO electrode in the fully reduced state, ESPANI/ITO electrode in the semi-oxidized state and PBPANI/ITO electrode in the fully oxidized state. The response sensitivity and stability of the three electrodes were investigated to determine the optimum doping potential; the response performance of the electrodes was tested for different doping times to determine the optimum preparation time. It is shown that the PBPANI/ITO electrode in the fully oxidized state has the optimum stability and response sensitivity at a doping time of 80 s. The electrode showed good linear response in the range of 1.00x10-5 ~ 1.00x10-1 M, with a response sensitivity of 37.30 dec/mV (R2 = 0.9966) and a detection limit of 10-5.6 M. The response time of the electrode to the solution was around 4 s, and it had good acid-base adaptability (pH 4.0 ~ 8.0). The performance of the prepared PBPANI/ITO electrode as a potentiometric phosphate sensor was also investigated in terms of stability (n = 10, RSD 1.76 %) and lifetime (6 weeks at room temperature), and was successfully used for phosphate detection and analysis in oilfield re-injection water, lake water and tap water samples in real environments with satisfactory results. (2) To further prepare a phosphate potential sensor with a high sensitivity response. We pretreated the home-made cobalt electrode with high pressure anodic oxidation in sodium hydroxide solution to produce a uniform cobalt oxide passivation film on the electrode surface. The sensitivity and stability of the response of the electrode at different pretreatment times were investigated to determine the optimum preparation conditions. The results showed that the pretreated cobalt electrode had a good response in the range of 1.00x10-5 ~ 1.00x10-1 M. The response sensitivity was 67.22 mV dec, R2 = 0.9939 and the detection limit was 10-5.5 M. It was much higher than that of the untreated cobalt electrode. This far exceeded that of the untreated polished cobalt electrode (36 ~ 40 mV/dec). The performance of the pretreated cobalt electrode as a potentiometric phosphate sensor was also investigated in terms of lifetime (7 weeks at room temperature), response rate (less 40 s), stability (n = 10, RSD 1.07 %) and acid-base adaptability (pH 4.0 ~ 8.0), and the sensor was successfully used for phosphate in oilfield re-injection water, lake water and tap water samples with satisfactory results.

(Invited) Electrochemically Driven Ion-Exchange Remediation of Water Containing High Fluoride Content

Remediation of water contaminated by anthropogenic activities is required to provide clean water for human consumption and prevent damage to the environment. The scale of the challenge is signaled by its inclusion in the UN 17 Sustainable Development Goals [1]. Major contributors to the problem are industrial activity and agriculture. The former commonly results in the release of metals; analysis and separation of such cationic species have received considerable attention [2]. In the latter instance, run-off of fertilizers used to enhance crop yields can result in unacceptable levels of nitrate or phosphate in natural waters. While monitoring of anionic species is widely undertaken using ion selective electrodes [3], the promise of electrochemical separation technologies [4] in this area is less well developed.For anthropogenic causes, remediation is the last resort following failure to prevent release of toxic materials into the environment. In contrast, there are instances where the “contaminant” is natural: fluoride is a prime example. The beneficial dental health effects of fluoride are widely appreciated, but excessive amounts are harmful to teeth, bones and various organs [5]. The World Health Organization (WHO) identifies the optimum fluoride level in drinking water to be 0.5-1.0 mg/L. In many regions, water is fluoridated to realize the health benefits. However, local geological conditions many countries can result in natural water fluoride levels significantly above the recommended upper limit of 1.5 mg/L.This presentation addresses the challenges associated with remediation of anions, with particular focus on fluoride. At the outset, it is recognized that for potable water the requirement is not full de-ionization but selective removal of contaminants: this is a separation challenge. The attributes, performance and potential for scale-up of a range of (electro)chemical remediation strategies will be discussed in general. We then focus on electrochemically switched ion-exchange (ESIX) [6], for which application to water softening [7] and perchlorate removal [8] has been demonstrated.We explore the facility of aniline-based (co-)polymer films to reversibly extract and eject fluoride ions as the charge (oxidation state) of the films are subject to electrochemical control. Homopolymer and copolymer films based on aniline, o-aminophenol and o-toluidine were deposited potentiodynamically. Film thickness was controlled via the number of potential cycles: the resultant electroactive site population was assayed coulometrically in monomer-free background electrolyte. Film mass was assayed gravimetrically using the EQCM. For relatively thin films, correlation of film mass and charge capacity revealed the solvent content. During deposition of thicker films, acoustic admittance data revealed the progressive evolution of viscoelastic effects. Co-monomer feedstock has a significant influence on film deposition rate, absolute solvent population and redox-driven solvent population change [9].The ion-exchange capacity of the films for redox-driven fluoride uptake was determined upon exposure to aqueous solutions of varying fluoride concentration, both in the absence and presence of chloride as a competing anion. EQCM mass and charge responses, respectively, provide overall “ion+solvent” and “solvent” population changes: correlation permits separation of fluoride and water uptake/release. Copolymer composition significantly influences the ease of fluoride uptake and release and reveals ion trapping. Complementary data on the dynamics of ion and solvent transfers are provided by shorter timescale experiments, involving voltammetry at faster scan rates and chronoamperometry. Correlation of gravimetric and coulometric data permits temporal separation of fluoride and solvent entry and exit.Practical exploitation of these promising fundamental observations will require scale-up and optimization of cycle life, film viscoelasticity and response time as functions of film thickness. We speculate that spatially variant film solvation will be a critical parameter. To this end, we consider the viability of neutron reflectivity measurements with isotopic substitution to determine the spatial distributions of fluoride and solvent in films of graded composition.

Planar, low-cost, flexible, and fully laminated graphene paper pseudo-reference and potassium-selective electrodes

We report for the first time a one-step fabrication by lamination of inexpensive graphene paper (GP) based Ag/AgCl pseudo-reference (RE) and K+-selective coated-film electrodes forming the novelty of this work. Contrary to our previous work about laminated GP solid-contact electrodes, the electrode fabrication in this work does not require manual drop casting steps after the lamination, simplifying the fabrication and making it suitable for mass production. We also eliminated the need of the solid contact and simplified the electrode construction by placing the plasticized potassium-selective PVC membrane (ISM) directly on the GP functioning as combined electrode substrate and ion-to-electron transducer. Both Ag/AgCl and the ISMs were pre-deposited on rectangular GP sheets (10 ×100 mm2) before placing them inside laminating pouches and feeding them through an office laminator after which the electrodes were ready for use. Five batches of 32 pseudo-REs had a very good E0 reproducibility of ± 2.8 mV. The K+-electrodes had a slope and detection limit of 57.4 ± 0.3 mV/pK (n = 4) and 6 × 10−7 M, and the E0 reproducibility was in the best case only ± 1.2 mV matching the performance of non-laminated K+-electrodes. This work demonstrates that the ISMs are compatible with the lamination where the temperature can momentarily rise to ca. 130 °C.

Evaluation of a Ru‐bipod Complex as a Redox Transducer for Membrane‐Based Voltammetry of Anions**

AbstractMolecular redox compounds show promise for the development of solid contact ion selective electrodes (SC‐ISEs) for anion determinations. In this work, a hydrophobic bis‐tridentate Ru‐bipod complex was studied as a molecular redox transducer in voltammetric SC‐ISEs. Thin film voltammetric behavior was achieved in films comprised of the Ru‐bipod complex, polyvinylchloride (PVC) and a plasticiser, nitrophenyloctylether (NPOE). Importantly, the choice of plasticiser had a significant effect on the SC‐ISE response of the Ru‐bipod complex; i. e., voltammetric responses of the Ru‐bipod complex in NPOE films were sharper and more intense than in bis(2‐ethylhexyl) sebacate (DOS) films. Moreover, addition of tetradodecylammonium tetrakis(4‐chlorophenyl)borate (ETH 500) to the membrane had an unfavorable impact on detection of anions due to oxidation of this salt in the film. Although the thin film electrode showed close‐to‐Nernstian behavior in anion responses, the detection responses in the presence of very hydrophilic anions such as sulfate ion were shifted to higher potentials (>1 V) with a subsequent loss of sensitivity. Overall, the Ru‐bipod complex operates as a simple transducer in SC‐ISEs with benefits in anion detection.

Graphitic Carbon Nitride/MOFs Hybrid Composite as Highly Selective and Sensitive Electrodes for Calcium Ion Detection.

The metal-organic framework (MOF) is a class of materials that exhibits a notable capacity for electron transfer. This unique framework design offers potential applications in various fields, including catalysis, gas storage, and sensing. Herein, we focused on a specific type of MOF called Ti-MOF. To enhance its properties and functionality, the composite material was prepared by incorporating graphitic carbon nitride (g-C3N4) into the Ti-MOF structure. This composite, known as g-C3N4@Ti-MOF, was selected as the active material for ion detection, specifically targeting calcium ions (Ca2+). To gain a comprehensive understanding of the structural and chemical properties of the g-C3N4@Ti-MOF composite, several analytical techniques were employed to characterize the prepared g-C3N4@Ti-MOF composite, including X-ray diffraction (XRD), SEM-EDX, and FT-IR. For comparison, different pastes were prepared by mixing Ti-MOF or g-C3N4@Ti-MOF, graphite, and o-NPOE as a plasticizer. The divalent Nernstian responses of the two best electrodes, I and II, were 28.15 ± 0.47 and 29.80 ± 0.66 mV decade-1, respectively, with concentration ranges of 1 µM-1 mM and 0.1 µM-1 mM with a content 1.0 mg Ti-MOF: 250 mg graphite: 0.1 mL o-NPOE and 0.5 mg g-C3N4@Ti-MOF: 250 mg graphite: 0.1 mL o-NPOE, respectively. The electrodes showed high sensitivity and selectivity for Ca2+ ions over different species. The suggested electrodes have been successfully employed for Ca2+ ion measurement in various real samples with excellent precision (RSD = 0.74-1.30%) and accuracy (recovery = 98.5-100.2%), and they exhibited good agreement with the HPLC.

Assessment and health risk of fluoride from Northeast Indian tea (Camellia sinensis L.): Fixing up the maximum residue level of fluoride in tea

The tea plant is considered a strong fluoride (F-) hyperaccumulator plant. We have proposed the Maximum Residue Limit (MRL) of F- in tea based on 321 tea samples collected from 8 tea-growing regions of Northeast India. Total F- as well as water-soluble F- content was analysed through the ion selective electrode with the recovery percentage of 100–108 to ascertain the risk associated with F- towards human health. It has been observed that total F- contents (mg kg−1) in Cachar, Darjeeling, Dooars, North Bank, South Bank, Terai, Tripura, and Upper Assam ranged from 42.5 to 111.5, 16.0 to 168.0, 48.0 to 291.0, 36.5 to 314.0, 60.0 to 154.0, 26.5 to 233.5, 26 to 118 and 44 to 244, respectively. The F- content in tea infusion varied between 1.08 mg L−1 and 2.43 mg L−1 across all eight regions with a mean of 1.90 mg L−1. The average transfer of F- from made tea (processed young shoot of tea plants comprising a bud and 2 to 3 leaves) to tea infusion was 100.46%. Fluoride content in infusion was decreased with the increment of infusion number but increased gradually with continuous infusion time. The non-carcinogenic health risk was assessed. Calculated Hazard Quotient values were far below 1. The calculated and rounded MRL (300 mg kg−1) was recommended for F- in tea in India.

MXene-Coated Ion-Selective Electrode Sensors for Highly Stable and Selective Lithium Dynamics Monitoring.

Lithium holds immense significance in propelling sustainable energy and environmental systems forward. However, existing sensors used for lithium monitoring encounter issues concerning their selectivity and long-term durability. Addressing these challenges is crucial to ensure accurate and reliable lithium measurements during the lithium recovery processes. In response to these concerns, this study proposes a novel approach involving the use of an MXene composite membrane with incorporated poly(sodium 4-styrenesulfonate) (PSS) as an antibiofouling layer on the Li+ ion selective electrode (ISE) sensors. The resulting MXene-PSS Li+ ISE sensor demonstrates exceptional electrochemical performance, showcasing a superior slope (59.42 mV/dec), lower detection limit (10-7.2 M), quicker response time (∼10 s), higher selectivity to Na+ (-2.37) and K+ (-2.54), and reduced impedance (106.9 kΩ) when compared to conventional Li+ ISE sensors. These improvements are attributed to the unique electronic conductivity and layered structure of the MXene-PSS nanosheet coating layer. In addition, the study exhibits the long-term accuracy and durability of the MXene-PSS Li+ ISE sensor by subjecting it to real wastewater testing for 14 days, resulting in sensor reading errors of less than 10% when compared to laboratory validation results. This research highlights the great potential of MXene nanosheet coatings in advancing sensor technology, particularly in challenging applications, such as detecting emerging contaminants and developing implantable biosensors. The findings offer promising prospects for future advancements in sensor technology, particularly in the context of sustainable energy and environmental monitoring.

β-Bi2O3-Bi2WO6 Nanocomposite Ornated with meso-Tetraphenylporphyrin: Interfacial Electrochemistry and Photoresponsive Detection of Nanomolar Hexavalent Cr.

Hexavalent chromium exposure via inhalation, ingestion, or both has been proven to adversely affect internal organs, induce toxic effects, cause allergies, and contribute to the development of cancer. It requires a substantial and challenging effort to detect several heavy metal ions conveniently, sensitively, and reliably by using materials that are easy to synthesize and have a high yield. The impact of light on the electrocatalytic oxidation/reduction process proves an environmentally friendly methodology with numerous applications in pollution control. The extensive use of photoactive materials in photoelectrochemical (PEC) sensors necessitates the development of stable and highly effective photoactive materials. Hence, the solvothermal synthesis of the organic-inorganic hybrid nanocomposite β-Bi2O3-Bi2WO6/H2TPP with varying weight percentages of meso-tetraphenylporphyrin (H2TPP) resulted in a selective electrode for electrocatalytic and photoelectrocatalytic reduction of Cr6+ on fluorine-doped tin oxide (FTO) by an adsorption-reduction mechanism. H2TPP increases the active site density and provides an effective surface area for efficient adsorption by providing both pyridinic- and pyrrolic-N atoms to β-Bi2O3-Bi2WO6/H2TPP. H2TPP could effectively adsorb Cr6+ in the β-Bi2O3-Bi2WO6/H2TPP composite system through electrostatic interaction, and the adsorbed Cr6+ ions were reduced to trivalent chromium Cr3+, resulting in promising Cr6+ sensing. The projected density of states and Bader charge calculations result in the electrostatic attraction among the N-2p orbital of H2TPP and the 3d and 4s orbitals of the Cr atom, resulting in the adsorption of the hexavalent Cr atom onto the active center of H2TPP. Moreover, the addition of H2TPP results in the development of a mesoporous surface that offers strong electrical conductivity, a substantial surface area, improved charge-mass transport, intimate contact between the electrolyte and catalyst, an extended fluorescence lifetime, and increased stability. The role of pH values was thoroughly investigated. All electrochemical and photoelectrochemical studies were carried out on 5 wt % H2TPP-ornated β-Bi2O3-Bi2WO6. Nanocomposite β-Bi2O3-Bi2WO6/5 wt % H2TPP demonstrated reliable cyclic stability, reproducibility, good sensitivity (8.005 μA mM cm-2), and a low limit of detection (LOD) (8.0 nM) toward photoelectrocatalytic reduction of Cr6+. The interference study in the presence of a few inorganic entities exhibited excellent selectivity. This tale amplification approach for developing a β-Bi2O3-Bi2WO6/5 wt % H2TPP nanocomposite system suggests a deeper understanding of the application of photoelectrocatalytic reduction of Cr6+ in environmental remediation with real samples under light irradiation.

Potentiometraic Method for Determining Biologically Non-Degradable Antimicrobial Substances

Ion selective electrodes (ISEs) based on polymer plasticized membranes have been developed for the determination of benzalkonium chloride (alkyldimethylbenzylammonium), the active component being cesium bis-octodecyl-2-sulfonio-closo-decaborate Cs[B10H9S(C18H37)2] (sensor A). For the determination of norfloxacin hydrochloride, the active component is potassium tris-octodecyl-1-ammonio-closo-decaborate K[B10H9N(C18H37)3] (sensor B). It has been shown that the electrodes have a reversible potentiometric response with respect to the analyzed cations in the presence of a number of other inorganic and organic cations. The influence of the concentration of the electrode-active substance on the electrochemical characteristics of the manufactured sensor has been studied. The optimal composition of the ion-sensitive membrane has been found. It has been determined that the developed sensors provide a wide range of detectable concentrations (for sensor A, 2 × 10–7–1 × 10–2; for sensor B, 1 × 10–7–1 × 10–2) and a low detection limit (for sensor A, 1 × 10–7 M; for sensor B, 8 × 10–8 M). New ISEs can be recommended for direct potentiometric detection of free ions in water bodies and water extracts of soils.

Functionalized Poly(azulenes) and Their Electrochromic Properties

AbstractIn this work, five 2‐ or 6‐ functionalized azulenes are electropolymerized to form azulene homopolymers. All five poly(azulenes) films exhibited electrochromism, with a two‐stage oxidation corresponding to the formation of the azulenium cation and the polaron, respectively. Electron‐donating groups at the 2‐position of azulene were found to greatly increase the poly(azulenes) film stability, with retention of optical contrast about four times as much as the 6‐alkylazulene analogue. This result demonstrates the potential of azulene functionalization as a strategy to improve the long‐term stability of electropolymerized azulenes, enabling applications in both optoelectronics as well as in ion selective electrodes.

New Ion Selective Electrodes for Analysis of Metformin Based on Molecularly Imprinted Polymers

Metformin (MEF) imprinted polymer liquid electrodes arecreated using a precipitation polymerization process. The MEF served as a template for the creation of molecularly imprinted (MIP) materials using benzoyl peroxide (BPO) as an initiator, allyl methacrylate (AMA) crosslinkers, and glycidyl methacrylate (GMA) as a monomer. UtilizingDi-octyl-phthalate (DOPH) and di-butyl phthalate (DBPH) as plasticizers in a PVC matrix, the molecularly imprinted membranes arecreated. The reaction time is approximately 50 seconds, and the limits of detection for liquid electrodes, as determined by the calibration curves, are 55.6 to 58.4 mV/decadeat 5×10-5M and 8×10-5M respectively. The liquid electrodes demonstrated good selectivity over a variety of species and a consistent reaction when filled with a typical 0.1 M drug solution across the pH range of 1 to 11. Modern electrodes can detect MEF without the need for time-consuming pre-treatment procedures in pharmaceutical samples.

Assessment of Particulate and Gaseous Fluoride in Phosphate Fertilizer Industry

Fluorides are emitted in both gaseous and particle forms in the industrial sector. However, studies usually only report total fluoride content. Therefore, the study aimed to assess the particulate, gaseous fluoride and correlate it with the respirable dust particles in Single Super Phosphate (SSP), Granular Single Super Phosphate (GSSP), and administration divisions of the industry. Respirable dust particles, particulate fluoride, and hydrogen fluoride in the work environment were collected on a filter cassette containing an MCE filter paper (0.8 micron 37-mm) and Na2CO3 impregnated backup pad, respectively, using a personal sampler. The fluoride samples were analyzed using Ion Selective Electrode (ISE) and expressed as milligrams per meter cube (mg.m-3). The respirable dust, particulate, and gaseous fluoride content were found to have statistically significant differences (p<0.001) between the divisions (SSP, GSSP, and administration) in the static monitoring, whereas, in the case of personal monitoring, no significant differences were observed. Average airborne respirable, particulate, and gaseous fluoride levels in static monitoring were 1.37, 1.03, 0.20 mg.m-3, 0.018, 0.008, 0.001 mg.m-3, and 0.808, 0.403, 0.026 ppm in SSP, GSSP and administration respectively, whereas in personal monitoring the average respirable, particulate and gaseous fluoride concentrations were 1.18, 0.85, 0.30 mg.m-3, 0.0013, 0.007, 0.002 mg.m-3 and 0.356, 0.258, 0.011 ppm in SSP, GSSP and administration respectively. The present study observed that the levels of fluoride decreased with an increase in distance from SSP, followed by GSSP and administration. It indicates that the fluoride exposure was inversely proportional to the distance of the source. This study outcome will help to design a policy and intervention to mitigate fluoride exposure among workers.

Role of Pre-Operative High-Resolution Computed Tomography for Surgical Planning in Patients Undergoing Cochlear Implantation - An Observational Study.

Currently preoperative magnetic resonance imaging (MRI) brain and High-Resolution Computed Tomography (HRCT) scanning of temporal bones form part of routine Cochlear implantation (CI) assessment. Pre- operative imaging demonstrates anatomic details or anomalies if any, that prove essential in pre-surgical evaluation of patients. These form a road map for the surgeon to anticipate any difficulty during surgery, to aid in decision making to implant the most appropriate ear, plan surgical technique, or select electrode arrays. A descriptive observational pilot study was conducted at tertiary care hospital involving 51 paediatric patients worked-up for CI. Patients after detailed clinical evaluation and MRI Brain, a tentative surgical plan was formulated by a candidacy CI screening committee. Patients selected for surgery underwent HRCT temporal bones and surgical plan was modified after analysing the same. Percentage of cases in which surgical plan changed (in terms of laterality of surgery) after correlating with HRCT findings were determined and data analysed. A total of 51 patients worked up for CI were included in the study. In 37.3% cases, there were unfavourable MRI findings. HRCT scan was used to aid the surgical road map in these patients, which based on MRI findings would have had suboptimal outcome. With this understanding, we recommend that, MRI with precise interpretation would be sufficient to furnish all necessary information in preoperative assessment of CI patients, and a HRCT temporal bones maybe indicated only in difficult cases or those with unfavourable MRI findings, may aid predict surgical events.

NH4+-selective electrode with superhydrophobic solid contact for actual wastewater monitoring

Ion-selective electrodes (ISEs) have significant superiority in monitoring water samples and various functional materials have been explored as solid contacts (SCs) to improve the detection reliability. However, water layer usually destroys the interfaces among electron collector, SCs and ion-selective membranes, especially in monitoring complicated actual wastewater, resulting in instability or loss of function. Here we demonstrate that surface hydrophobization of SCs is a feasible approach to minimize adverse effect of water layer on unstable SCs adhered to electron collector, ensuring long-term reliability of ISEs in actual wastewater monitoring. Though NH4+-ISE with MoOx @polyaniline composite SC has low standard deviations (SDs) of the standard potential (E0) measured in NH4+ standard solutions, Nernstian slopes are dramatically reduced from 58.66 to 27.65 mV/dec after 16-day actual wastewater monitoring. Accordingly, measured NH4+ concentrations of actual wastewater have a high degree of inaccuracy up to ca. 850%. In contrast, the ISE with a superhydrophobic SC has a slope closer to the ideal Nernstian slope, lower potential drift and E0 SDs, and higher resistance against external interferences, due to water layer inhibition of the SC. Importantly, superhydrophobic SC-ISE shows a near-Nernstian response in steady state and accurate NH4+ concentration determination during 30-day actual wastewater monitoring.

A comparative study of green solid contact ion selective electrodes for the potentiometric determination of Letrozole in dosage form and human plasma

Analysis of drugs clinically and their identification in biological samples are of utmost importance in the process of therapeutic drug monitoring, also in pharmacokinetic investigations and tracking of illicit medications. These investigations are carried out using a variety of analytical methods, including potentiometric electrodes. Potentiometric electrodes are a wonderful solution for researchers because they outperform other methods in terms of sustainability, greenness, and cost effectiveness. In the current study, ion-selective potentiometric sensors were assembled for the aim of quantification of the anticancer drug Letrozole (LTZ). The first step was fabrication of a conventional sensor based on the formation of stable host–guest inclusion complex between the cationic drug and 4-tert-butylcalix-8-arene (TBCAX-8). Two additional sensors were prepared through membrane modification with graphene nanocomposite (GNC) and polyaniline (PANI) nanoparticles. Linear responses of 1.00 × 10–5–1.00 × 10–2, 1.00 × 10–6–1.00 × 10–2 and 1.00 × 10–8–1.00 × 10–3 with sub-Nernstian slopes of 19.90, 20.10 and 20.30 mV/decade were obtained for TBCAX-8, GNC, and PANI sensors; respectively. The developed sensors were successful in determining the drug LTZ in bulk powder and dosage form. PANI modified sensor was used to determine LTZ in human plasma with recoveries ranging from 88.00 to 96.30%. IUPAC recommendations were followed during the evaluation of the electrical performance of the developed sensors. Experimental conditions as temperature and pH were studied and optimized. Analytical Eco-scale and Analytical GREEness metric were adopted as the method greenness assessment tools.

Evaluation of fluoride levels in areca nut, tobacco, and commercial smokeless tobacco products: a pilot study

Oral submucous fibrosis (OSMF) is a premalignant condition associated with chewing areca nut and tobacco products. We observed increased fluoride levels in some OSMF-endemic regions,and the observation suggested that fluoride exposure may contribute to its pathogenesis. This study aimed to assess the fluoride content of various smokeless tobacco items as a potential influencing source. Fluoride concentration was analysed in commercial areca nut products, including gutkha, pan masala, and raw areca nut, along with tobacco, slaked lime, and catechu samples from Karnataka, India. Fluoride was measured using alkali fusion and the ion selective electrode method. All products showed high fluoride, with catechu having the highest mean concentration at 51.20 mg/kg, followed by tobacco, gutkha, pan masala, processed areca nut, and raw areca nut. Fluoride was also elevated in soil, but not in water. The findings demonstrate substantial fluoride levels in popular types of smokeless tobacco, and highlight an overlooked source of exposure among consumers of gutkha, pan masala and similar oral tobacco-products. The fluoride content warrants an investigation of potential links with the occurrence and severity of OSMF.

Fluoridated orthodontic adhesives: Implications of release and recharge and their impact on shear bond strength in demineralized tooth surfaces.

This study measured fluoride release from a light-cured orthodontic adhesive resin (Vega type) at three time intervals (one day, one week, and one month), investigated the rechargeability of the resin, and assessed its impact on shear bond strength in demineralized tooth surfaces. This study used 30 recently extracted upper premolar teeth to explore the effects of fluoride release over specific time intervals. The teeth underwent demineralization and were categorized into groups based on time intervals: one day, one week, and one month. Subgroups within each interval underwent fluoride recharging through fluoride varnish application. Fluoride release and shear bond strength were assessed after etching with phosphoric acid gel, applying the orthodontic adhesive, and curing. The samples were stored in deionized water. Fluoride quantification used a selective electrode, while shear bond strength assessment employed a universal testing machine. Finally, statistical analysis of the data was performed using SPSS 22. The study found that after one month, the adhesive had the highest fluoride release and shear bond strength mean values. There were significant differences in fluoride release and shear bond strength between the various groups studied. The application of fluoride varnish around the orthodontic bracket resulted in a positive effect on the shear bond strength of the bracket.

A low-cost portable system for on-site detection of soil pH and potassium levels using 3D printed sensors

Accurate data on the nutrient content of soil is essential for optimum fertiliser application in agriculture. Frequent and regular soil tests hold the key to mitigate difficulties that arise from lack of accurate information for soil and crop management, such as increased costs for fertilisers, and environmental degradation. Traditionally soil nutrient contents levels are measured from laborious methods which involves collecting field samples and returning to the laboratory for analysis. Laboratory analysis often requires sample pre-treatment, chemical extractants and expensive instrumentation. A low-cost on-site detection method for soil nutrients can increase data necessary for smart fertiliser application that can in turn increase farm profit and ensure environmental protection. Here we present a low-cost miniaturised multi-ion sensing system for on-site detection of pH and potassium. The sensing system consists of a PSoC4 microcontroller and novel 3D printed miniaturised ion selective electrodes for the simultaneous determination of potassium and pH. The 3D printed electrode's pH sensing capability and potassium ion sensing was validated using known pH and potassium ion concentrations, exhibiting high selectivity and excellent Nernstian sensitivities for pH (−61.05 mV/pH) and potassium (49.50 mV/decade). Soil pore water samples from various locations and depths were extracted using a MacroRhizon sampler and tested using the novel portable detection system. On-site pH and potassium determinations were acquired in extremely small volumes samples without the requirement of sample preparation.