Potentiometric Ion-selective Electrodes Research Articles

Enhancing the Sustainability of Eco-Friendly Potentiometric Ion-Selective Electrodes for Stability-Indicating Measurement of Ethamsylate: Application in Bulk and Pharmaceutical Formulations.

Through the use of sustainable and green chemistry concepts, scientists need to decrease waste, conserve energy, and develop safe substitutes for hazardous compounds, all for protecting and benefiting society and the environment. Four novel eco-friendly ion selective electrodes (ISE) were generated to determine Ethamsylate (ETM) in bulk powder and different pharmaceutical formulations. The present electrodes were fabricated to clearly distinguish ETM from a variety of inorganic, organic ions, sugars, some common drug excipients and the degradation product, hydroquinone (HQ) of ETM, and thus used for stability-indicating methods. The electrodes fabrication was based on 2-nitrophenyl octyl ether (NPOE) that was employed as a plasticizer in electrodes 1, 2, and 3 within a polymeric matrix of polyvinyl chloride (PVC) except for electrode 4, in which dibutyl sebacate was used as a plasticizer. Electrodes 1 and 2 were fabricated usingtetradodecylammonium bromide as an anionic exchanger, adding 4-sulfocalix-8-arene as an ionophore only to electrode 2 and preparing electrode 1 without incorporation of an ionophore. The fabrication of electrodes 3 and 4 was based on ethamsylate-tetraphenylborate (ETM-TPB) as an ion-association complex in a PVC matrix. The environmental sustainability was assessed using the green analytical procedure index (GAPI), and analytical greenness metric for sample preparation (AGREEprep). Electrodes 1 and 2 had linear dynamic ranges of 10-1-10-5 mol/L and 10-1-10-4 mol/L, respectively, with a Nernstian slope of 49.6 and 53.2 mV/decade, respectively. Electrodes 3 and 4 had linear dynamic ranges of 10-1-10-4 mol/L, with a Nernstian slope of 43.9 and 40.2 mV/decade, respectively. The electrodes' selectivity coefficients showed good selectivity for ETM. The utility of 4-sulfocalix-8-arene as an ionophore had a significant influence on increasing the membrane sensitivity and selectivity of electrode 2 compared to other electrodes. Four novel eco-friendly ISEs were used for determination of ETM in bulk powder and different pharmaceutical formulations. Different experimental parameters were performed to optimize the determination conditions such as solvent mediators, dynamic response time, effect of pH, and temperature. Stability-indicating measurement of ETM in the presence of its degradate HQ and co-formulated drug tranexamic acid. Using new ecological assessment tools to determine whiteness and greenness profiles.

A mixed electronic-ionic conductor-based bifunctional sensing layer beyond ionophores for sweat electrolyte monitoring

Noninvasive and continuous monitoring of electrolytes in biofluids based on wearable biotechnology provides extensive health-related physiological information. The state-of-the-art wearable bioelectronic ion sensors depend on the organic ionophore-based solid-contact structure of potentiometric ion-selective electrodes. This structure contains two functional sensing layers, i.e., a solid contact (ion-to-electron signal transduction) and an ionophore-containing ion-selective membrane (ISM, ion recognition). However, the potential drift, biotoxicity, and expensive organic ionophores complicate practical wearable applications. These challenges intrinsically originate from the ISM. Herein, an ISM-free wearable ion sensor based on mixed electronic-ionic conductors of tungsten bronzes is reported. These materials can serve as a bifunctional sensing layer for simultaneous ion-to-electron transduction through the redox reaction of W6+/5+ and ion recognition through crystal ion exchange. The K- and Na-adjusted WO3 disclosed Nernstian responses toward NH4+ and H+, respectively. The selectivity is comparable to or even better than organic ionophores, such as ammonia ionophore of nonactin. Further, the on-body monitoring of sweat ammonia and pH was realized using an integrated ISM-free flexible sensor. Therefore, this work offers an ISM-free concept and emphasizes the importance of developing next-generation ISM-free wearable bioelectronic ion sensors.

In Situ Drift Monitoring and Calibration of Field-Deployed Potentiometric Sensors Using Temperature Supervision.

Potentiometric ion-selective electrodes (ISEs) have broad applications in personalized healthcare, smart agriculture, oil/gas exploration, and environmental monitoring. However, high-precision potentiometric sensing is difficult with field-deployed sensors due to time-dependent voltage drift and the need for frequent calibration. In the laboratory setting, these issues are resolved by repeated calibration by measuring the voltage response at multiple standard solutions at a constant temperature. For field-deployed sensors, it is difficult to frequently interrupt operation and recalibrate with standard solutions. Moreover, the constant surrounding temperature constraint imposed by the traditional calibration process makes it unsuitable for temperature-varying field use. To address the challenges of traditional calibration for field-deployed sensors, in this study, we propose a novel in situ calibration approach in which we use natural/external temperature variation in the field to obtain the time-varying calibration parameters, without having to relocate the sensors or use any complex system. We also develop a temperature-supervised monitoring method to detect the drift of the sensor during operation. Collectively, the temperature-based drift monitoring and in situ calibration methods allow us to monitor the drift of sensors and correct them periodically to achieve high-precision sensing. We demonstrate our approach in three testbeds: (1) under controlled temperature variation in the lab, (2) under natural temperature variation in a greenhouse, and (3) in the field to monitor nitrate activity of an agricultural site. In the laboratory study, we validate that the calibration parameters of printed nitrate ISEs can be reproduced by our proposed calibration process; therefore, it can serve as an alternative to traditional calibration processes. In the greenhouse, we show the use of natural temperature variation to calibrate the sensors and detect the drift in a fixed concentration nitrate solution. Finally, we demonstrate the use of the method to monitor the nitrate activity of an agricultural field within 10% of laboratory-based measurements (i.e., a sensitivity of 0.03 mM) for a period of 22 days. The findings highlight the prospect of temperature-based calibration and drift monitoring for high-precision sensing with field-deployed ISEs.

Inkjet-Printed Soft Intelligent Medical Bracelet for Simultaneous Real-Time Sweat Potassium (K+), Sodium (Na+), and Skin Temperature Analysis

Truly wearable, fully flexible, multi-parametric sweat analysis with soft and socially discrete packaging offers tremendous potential to enable the next generation of non-invasive digital biomarkers analysis. Several examples of miniaturized potentiometric ion selective electrodes (ISE) have been proposed. However, several challenges remain unsolved concerning their long-term stability due to variations in physical sweat parameters. We hypothesize that the simultaneous monitoring of such parameters (e.g., skin-surface temperature, sweat rate, and pH) may pave the way for accurate and robust sweat biomarker analysis. Therefore, we propose a flexible multiparameter sensory interface fabricated on Kapton polyimide (PI) foil with high-resolution inkjet printing using silver nanoparticles (AgNPs). A facile controlled drop-casting of a custom synthesized ion-selective membrane ensures the selectivity of the biosensing. Next, we interfaced the fabricated sensory array with a custom-designed compact flexible biosignals conditioning embedded system, which enables system calibration, data processing, and wireless data transmission to a smartphone device. Later, we validate the proposed system in simultaneous sweat multi-ion (K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) and skin-surface temperature recording. After that, we characterize the system by embedding the smart medical bracelet in a soft microfluidic platform to mimic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> analysis on the body. Overall, the reported results represent the fundamental evidence proof for the development of the wearable multimodal sweat parameter analyzer.

Uncertainty of Postmortem Time Estimation Based on Potassium Ion Determination in Vitreous Humor Using Potentiometric Ion-Selective Electrode and Microwave-Induced Plasma with Optical Emission Spectrometry Methods

There is a need for a reliable and independent evaluation and confirmation of the postmortem interval (PMI) based on objective factors other than only postmortem changes or temperature measurements. Estimating the PMI by examining the concentration of potassium ions in the vitreous humor (VH) has a tradition in forensic toxicology dating back to the mid-20th century. So far, the methods for determining the presence of potassium ions have not been characterized in terms of the measurement uncertainty of types A and B, which directly affect the estimation of time of death uncertainty. The study evaluated the uncertainty of the determination of potassium ion concentrations using potentiometric ion-selective electrode (ISE) and microwave-induced plasma with optical emission spectrometry (MIP-OES) methods. In addition, the influence of the estimated measurement uncertainty on the results of the analysis of potassium ions in the VH was investigated. The estimated values of the expanded uncertainty determined by the type A experimental method indicate lower uncertainty in the determination of potassium ion concentration in the case of MIP-OES than ISE; that is, for concentrations of 2, 10, and 25 mg/L of potassium ions, the expanded uncertainties by MIP-OES were 1.2%, 2.2%, and 2.5% and the uncertainties by ISE were 12.2%, 6.1%, and 3.1%, respectively. Similarly, in the case of estimating the uncertainty of type B, the MIP-OES method compared to ISE was characterized by almost two times lower expanded uncertainty; that is, for MIP-OES, it was 2.53%, and for ISE, it was 4.75%. Both methods of uncertainty estimation, types A and B, can be used interchangeably, as they provide comparable results.

Green Assay of Tolmetin Sodium Using Solid Contact Potentiometric Sensor Doped with Ionophore and Supported with Docking Study: Application to Human Plasma and Pharmaceutical Formulations

Tolmetin sodium (TOL) is a non-steroidal anti-inflammatory drug used to treat arthritis. Potentiometric ion selective electrodes (ISEs) bypass sample pre-treatment, high-tech apparatus, and toxic chemicals. The current study aimed to develop and validate a potentiometric analyser for the direct assay of TOL in pharmaceutical dosage form and human plasma. We designed an experimental approach to determine the factors that affect the performance of the developed sensor. A solid contact glassy carbon electrode was utilized as a support for the developed sensor. The interaction of TOL with several ionophore was studied using molecular docking. The optimized sensor was fabricated using dioctyl phthalate as plasticizer, tetra dodecyl ammonium bromide as anion exchanger, and β cyclodextrin as ionophore.The sensor achieved −58.78 Nernstian response within 1.00 × 10−2–2.00 × 10−6 mol l−1 linear range, 1.56 × 10−6 mol l−1 LOD, and fast response within 7 s. The greenness of the proposed method was assessed using the Analytical Eco-scale and the “Green Analytical Procedure Index” (GAPI) metric tools and compared with the reported methods and gained high scores. The proposed method has several advantages in encouraging quality control and clinical labs to routinely use the developed sensor in the assay of TOL in pharmaceutical dosage forms and human plasma.

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

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

Temperature Self-Calibration of Always-On, Field-Deployed Ion-Selective Electrodes Based on Differential Voltage Measurement.

Originally developed for use in controlled laboratory settings, potentiometric ion-selective electrode (ISE) sensors have recently been deployed for continuous, in situ measurement of analyte concentration in agricultural (e.g., nitrate), environmental (e.g., ocean acidification), industrial (e.g., wastewater), and health-care sectors (e.g., sweat sensors). However, due to uncontrolled temperature and lack of frequent calibration in these field applications, it has been difficult to achieve accuracy comparable to the laboratory setting. In this paper, we propose a novel temperature self-calibration method where the ISE sensors can serve as their own thermometer and therefore precisely measure the analyte concentration in the field condition by compensating for the temperature variations. We validate the method with controlled experiments using pH and nitrate ISEs, which use the Nernst principle for electrochemical sensing. We show that, using temperature self-calibration, pH and nitrate can be measured within 0.3% and 5% of the true concentration, respectively, under varying concentrations and temperature conditions. Moreover, we perform a field study to continuously monitor the nitrate concentration of an agricultural field over a period of 6 days. Our temperature self-calibration approach determines the nitrate concentration within 4% of the ground truth measured by laboratory-based high-precision nitrate sensors. Our approach is general and would allow battery-free temperature-corrected analyte measurement for all Nernst principle-based sensors being deployed as wearable or implantable sensors.

A smartphone-assisted hybrid sensor for simultaneous potentiometric and distance-based detection of electrolytes

At home electrolyte analysis is of growing interest due to the importance for early diagnosis for various diseases. This work presents the first device that integrates a potentiometric ion-selective electrode (ISE) with distance-based colorimetric detection for the simultaneous analysis of K+ and Cl− ions at the point of care (POC). This hybrid sensing device was designed in a two-dimensional configuration using a plastic transparency sheet containing a stencil printed K+-ISE and a paper substrate for distance-based colorimetric detection of Cl−. K+ quantification was performed using a low-cost (<$25) lab-made Wi-Fi supported potentiometer with a custom smartphone application while Cl− ions were quantified with an instrument-free distance-based paper analytical device (dPAD). The total analysis time is 5 min once the sample is added. The K+-ISE showed a sensitivity of 55.89 ± 2.52 mV/decade from 0.1 to 100 mM with a limit of detection (LOD) of 0.01 mM. The linear working range for Cl− detection was 0.5–50 mM whereas the LOD was 0.16 ± 0.05 mM. The proof-of-concept application of the sensing hybrid device was demonstrated in human urine and artificial sweat samples containing K+ and Cl− ions at physiologically relevant ranges. The recoveries were found to be 88–108% for K+ and 90–104% for Cl−, showing the potential use of the proposed device for low-cost routine analysis of biological samples at POC.

Hydrophobic laser-induced graphene potentiometric ion-selective electrodes for nitrate sensing.

Current solid-contact ion-selective electrodes (ISEs) suffer from signal-to-noise drift and short lifespans partly due to water uptake and the development of an aqueous layer between the transducer and ion-selective membrane. To address these challenges, we report on a nitrate ISE based on hydrophobic laser-induced graphene (LIG) coated with a poly(vinyl) chloride-based nitrate selective membrane. The hydrophobic LIG was created using a polyimide substrate and a double lasing process under ambient conditions (air at 23.0 ± 1.0°C) that resulted in a static water contact angle of 135.5 ± 0.7° (mean ± standard deviation) in wettability testing. The LIG-ISE displayed a Nernstian response of - 58.17 ± 4.21mV dec-1 and a limit-of-detection (LOD) of 6.01 ± 1.44µM. Constant current chronopotentiometry and a water layer test were used to evaluate the potential (emf) signal stability with similar performance to previously published work with graphene-based ISEs. Using a portable potentiostat, the sensor displayed comparable (p > 0.05) results to a US Environmental Protection Agency (EPA)-accepted analytical method when analyzing water samples collected from two lakes in Ames, IA. The sensors were stored in surface water samples for 5weeks and displayed nonsignificant difference in performance (LOD and sensitivity). These results, combined with a rapid and low-cost fabrication technique, make the development of hydrophobic LIG-ISEs appealing for a wide range of long-term in situ surface water quality applications.

Steady-State and Transient Performance of Ion-Sensitive Electrodes Suitable for Wearable and Implantable Electro-Chemical Sensing.

Traditional Potentiometric Ion-selective Electrodes (ISE) are widely used in industrial and clinical settings. The simplicity and small footprint of ISE have encouraged their recent adoption as wearable/implantable sensors for personalized healthcare and precision agriculture, creating a new set of unique challenges absent in traditional ISE. In this paper, we develop a fundamental physics-based model to describe both steady-state and transient responses of ISE relevant for wearable/implantable sensors. The model is encapsulated in a "generalized Nernst formula" that explicitly accounts for the analyte density, time-dynamics of signal transduction, ion-selective membrane thickness, and other sensor parameters. The formula is validated numerically by self-consistent modeling of multispecies ion-transport and experimentally by interpreting the time dynamics and thickness dependence of thin-film solid-contact and graphene-based ISE sensors for measuring soil nitrate concentration. These fundamental results will support the accelerated development of ISE for wearable/implantable applications.

All-solid-state potassium-selective sensor based on carbon black modified thermoplastic electrode

Thermoplastic carbon composite electrodes have been introduced by our group as novel electrodes with improved electrochemical properties and previously applied for accurate detection of biomarkers using voltammetric methods. Because of their exceptional properties, we hypothesized they would work well as potentiometric ion-selective electrodes as well. In this work, potassium selective thermoplastic electrodes (TPEs) were developed for potentiometric detection for the first time and applied in biofluids. TPEs were fabricated using mixture of polystyrene and polycaprolactone and two types of graphite (MG1599 and Nano19) for comparison, and modified with carbon black via drop-casting. Carbon black modification was optimized in the presence of various numbers of carbon black layers, while ion selective membrane components were optimized at different component ratios. Under optimized conditions, TPEs exhibited Nernstian response to K+ with sensitivity of 59.3 ± 1.01 mV decade−1 and near-Nernstian response with sensitivity of 56.8 ± 1.7 mV decade−1 within a linear range of 1.0 × 10−4 M-1.0 × 10−1 M with a LOD of 1.0 × 10−4- M for Nano19- and MG1599-based TPEs, respectively. The K+-selective TPEs demonstrated rapid response (4 s) and excellent stability, repeatability and reproducibility. The applicability of electrodes were shown in human pooled urine and artificial interstitial fluid samples with potassium ion concentrations ranging from healthy and unhealthy levels. Therefore, the electrodes could be used in healthcare applications for accurate detection of K+ exists in complex matrix and can be easily adapted to simultaneously monitor other ions for diagnosis of diseases due to miniaturization of TPEs.

Selective Determination of Nicorandil with a Single Planar Solid‐state Potentiometric Ion Selective Electrode

AbstractNovel screen‐printed electrodes (SPEs) were constructed for the quantitation of nicorandil (NIC) in its pharmaceutical formulations. Different ion‐exchangers and plasticizers were investigated, but the optimal potentiometric response was obtained using nicorandil‐phosphotungstate (NIC‐PTA) ion associate and tricresyl phosphate as a plasticizer. A Nernstian response of 58.80±1 mV/decade was obtained over a concentration range of (1×10−6–1×10−2) M with 1×10−5 M as a detection limit. Sensor morphology was characterized using scanning electron microscopy (SEM). The method was validated for the assay of NIC with high selectivity, accuracy (average recovery=100.54 %), and precision (%RSD≤2).

A Paper-Based Potentiometric Platform for Determination of Water Hardness

A novel paper-based potentiometric platform for the simple and fast monitoring of water hardness is presented. First, potentiometric ion-selective electrodes for calcium and magnesium printed on a paper substrate were built and optimized. These sensors, which display near-Nernstian sensitivity, were used for the determination of the concentration of these cations and the calculation of the water hardness. Second, the incorporation of a solid-state reference electrode allowed building an integrated paper-based potentiometric cell for the determination of the hardness of artificial and real samples (mineral waters). The validation of the results shows good ability to predict hardness in the conventional scale. Truly decentralized measurements were demonstrated by integration of a miniaturized instrument and dedicated software in a portable device. The measurements were able to be performed in just under two minutes, including a two-point calibration. Since the method is simple to use and cost-effective, it can be implemented in domestic and industrial settings.

Recent Advances in Electrochemical Sensors for Wearable Sweat Monitoring: A Review

Thanks to rapid technological innovation over the last decade, a wide range of wearable devices have emerged, playing an inspiring role in healthcare, diagnostics, and sports monitoring. This review summarizes recent progress in the development and application of electrochemical (EC) sweat sensors and self-powered systems for wearable applications. Presented here are the most common types of EC sweat sensors, namely potentiometric ion-selective electrodes, amperometric enzymatic and non-enzymatic sensors, as well as differential pulse voltammetric sensors. The sensing principle and novel functional nanomaterials that are used to enhance the performance of wearable sweat sensors and their applications are summarized. The recent advancement of battery-free wearable devices is presented, including self-powered biofuel cells (BFC), energy harvesting from novel materials and its strategy, are also discussed. The challenges in, and opportunities for, the development of sweat sensor-based wearable systems moving forward are reviewed, with the aim of shedding some light on future directions.

Novel dalfampridine-selective green potentiometric membrane sensors for in-line dissolution profiling of its extended release tablets

Dissolution profiling of solid oral dosage forms is currently a mandatory analytical practice in pharmaceutical industry worldwide. Classically, this test is performed employing time-consuming, destructive and high waste generating conventional off-line separation-based techniques. Accordingly, this work is motivated with the ultimate objective of exploiting the unique capabilities of in-line potentiometric ion selective electrodes (ISEs) as greener alternative for monitoring the drug dissolution pattern. Novel Dalfampridine (FAM) potentiometric polyvinyl chloride (PVC) membrane sensors were fabricated with different cation exchangers, ionophores and plasticizers, and systematically optimized via comparing the sensors performance. Fabricated sensor based on potassium tetrakis (4-chlorophenyl) borate as cation exchanger plasticized with 2- nitrophenyl octyl ether and calix[6]arene as ionophore in a PVC matrix proved to possess high sensitivity with limit of detection of 1.78 × 10−5 mol L−1, a Nernstian slope of 57.40 mV/decade and fast response time within a concentration range of 2.0 × 10−5–1.0 × 10−2 mol L−1. Sensor performance was assessed as per IUPAC recommendation and applied successfully for determination of FAM in its pure form and Fampyra® tablets without the need for any sample pretreatments. Additionally, real time in-line monitoring of the dissolution profile of Fampyra® tablets using U.S Food and Drug Administration dissolution parameters was attained. Finally, the environmental impact of the proposed method was compared to a classical off-line HPLC dissolution strategy using newly developed tool for assessing method greenness; green analytical procedure index (GAPI).

Electrochemical detection of trace silver

Increasing utilization of silver and silver nanoparticles (AgNPs) in daily processes and products has led to a significant growth in scientific interest in methods for monitoring silver. In particular, the amount of silver ions (Ag+) released to the environment is known to have a detrimental effect on aquatic ecology, and thus some control actions have been implemented in recent years; for example, the manufacturing industry is now required to control and certify the quantity of AgNPs present in products. Electrochemical sensors are well suited to the task of silver monitoring due to several beneficial properties, including low costs, fast measurements, and facile adaptation to miniaturized, portable instrumentation. The predominant method for electrochemical silver determination involves potentiometric ion selective electrodes (ISEs) and voltammetric measurements. Reviewing the literature of the last ten years reveals significant improvements in the analytical performance of electrochemical sensors, mainly related to the development of new protocols, selective receptors, and electrode materials. Remarkably, ISEs with limits of detection (LOD) in the nanomolar range have been reported, employing careful control of ion fluxes across the membrane interfaces. What's more, sub-nanomolar LODs are attainable by stripping voltammetry using either ligand-based deposition strategies or thin layer membranes coupled to conducting polymers. Selectivity has also been optimized through the membrane composition of ISEs, with special focus on Ag+ ionophores. Furthermore, novel voltammetric methods allow for discrimination between Ag+ and AgNPs. However, there is still a dearth of studies applying such electrochemical sensors to on-site water analysis, and hence, further research is needed in order to translate these laboratory scale achievements to real-world contexts. Overall, this review describes the state-of-the-art in electrochemical silver detection, and provides a comprehensive description of those aspects contributing to the further development and improvement of analytical performance.

Optimized ion selective electrode for determination of Tamsulosin hydrochloride in the presence of co-formulated Deflazacort in bulk, tablet dosage form and human urine

Direct analytical methods offer an excellent tool for rapid determination of pharmaceuticals without deviation from the green analytical chemistry principles. In this work, a potentiometric ion selective electrode (ISE) method for the selective determination of the α1A-adrenoceptor blocker, Tamsulosin HCl was developed, optimized and assessed for greenness. Six different PVC-membrane sensors were fabricated using 2-nitrophenyl octyl ether (NPOE) as a plasticizer. Three ion exchangers were used, namely sodium tetraphenyl borate (Na.TPB), sodium tetrakis- [3,5-bis (trifluoro- methyl) phenyl] borate (Na.Tetrakis) and ammonium reineckate (Amm. RK) in exchange with the two ionophores, 4-tert-Butylcalix [8] arene (Calix.) and 2-hydroxypropyl-β-cyclodextrin (β-CD). The electrochemical responses of all sensors were studied and recorded. The sensor which consisted of sodium tetraphenyl borate as ion exchanger and 4-tert-Butylcalix [8] arene as ionophore was selected for application to analysis of Tamsulosin HCl in dosage form and human urine. The electrochemical performance characteristics of the electrode were validated as per IUPAC recommendations. Analytical Eco Scale assessment was used for evaluation of the greenness of the method and compared with the USP official method for the determination of Tamsulosin HCl.

A Novel Potentiometric Ion Selective Electrode Based on Piperine for the Determination of Fe(III) Ions

A new potentiometric sensor highly selective to Fe3+ was prepared using piperine as a neutral ionophore. The electrode exhibits a linear response for Fe3+ ions in the citrate buffer medium over a concentration range from 1 × 10–4 to 1 M (detection limit of 6 × 10–5 M) with a Nernstian slope of 20.5 mV per decade. The electrode can be successfully used in the pH range of 3.15–7.85. It has a fairly good discriminating ability toward Fe3+ ions among some other metal ions such as K+, Ca2+, Mg2+, Cu2+, Ba2+, Co2+, Al3+ and Cr3+ with selectivity coefficients of –2.11, –9.02, –10.38, –8.34, –8.12, –8.79, –8.41 and –3.69, respectively. The electrode can be used for 10 weeks without any considerable divergence in the observed slope. It has been successfully validated using atomic absorption spectrometry and used in the determination of Fe3+ in chewable iron capsules.

Fluoride Exposure and the Effect of Tobacco Smoking on Urinary Fluoride Levels in Primary Aluminum Workers

Workers in primary aluminum smelter are exposed to fluoride from cryolite (Na3AlF6) used in the electrolysis process. Post-shift urinary fluoride is considered as an appropriate index for examination of fluoride exposure. The objective of the study was to investigate the exposure to fluoride in primary aluminum smelter in Žiar nad Hronom (Slovakia) during three consecutive two-year periods between 2012 and 2018. The relationship between fluoride exposure in the occupational environment, tobacco smoking, and pre- and post-shift urinary fluoride concentration was investigated in 76 male workers in the ages from 21 to 60 years. Workers were monitored by personal fluoride sampling equipment. Their urinary samples were collected prior to the start and at the end of an eight-hour shift. Fluoride content in urine samples was analyzed by potentiometric ion-selective electrode and expressed as weight ratio of fluoride content to creatinine. The Mean ± SD particulate fluoride concentration in occupational air was 0.966 ± 1.658 mg/m3 and gas-phase fluoride concentration was 0.327 ± 0.809 mg/m3. Mean urinary fluoride concentration of all workers was significantly higher (p &lt; 0.001) after the eight-hour shift. Smokers tended to have a higher post-shift mean urinary fluoride concentration than non-smokers, but this difference was not statistically significant (p = 0.11). The difference between these two groups of workers was also not statistically significant (p = 0.62) before the shift. Therefore, according to results, smoking caused no statistically significant difference in urinary fluoride levels between the group of smokers and group of non-smokers in primary aluminum workers.