SPOOC (Sensor for Periodic Observation of Choline): An Integrated Lab-on-a-Spoon Platform for At-Home Quantification of Choline in Infant Formula.

Choline is an essential micronutrient for infants' brain development and health. To ensure that infants receive the needed daily dose of choline, the U.S. Food and Drug Administration (FDA) has set requirements for choline levels in commercialized infant formulas. Unfortunately, not all families can access well-regulated formulas, leading to potential inadequacies in choline intake. Economic constraints or difficulties in obtaining formulas, exacerbated by situations like COVID-19, prompt families to stretch formulas. Accurate measurement of choline in infant formulas becomes imperative to guarantee that infants receive the necessary nutritional support. Yet, accessible tools for this purpose are lacking. An innovative integrated sensor for the periodic observation of choline (SPOOC) designed for at-home quantification of choline in infants' formulas and milk powders is reported. This system is composed of a choline potentiometric sensor and ionic-liquid reference electrode developed on laser-induced graphene (LIG) and integrated into a spoon-like device. SPOOC includes a micro-potentiometer that conducts the measurements and transmits results wirelessly to parents' mobile devices. SPOOC demonstrated rapid and accurate assessment of choline levels directly in pre-consuming infant formulas without any sample treatment. This work empowers parents with a user-friendly tool for choline monitoring promoting informed nutritional decision-making in the care of infants.

Application of ionic liquids in ion-selective electrodes and reference electrodes: A review.

Ionic liquids (ILs) are organic chemical compounds that are composed only of ions, a large organic cation and a smaller inorganic or organic anion. These are salts whose melting point is lower than the boiling point of water. ILs have many interesting properties, thanks to which they find great practical applications in analytics, electrochemistry, separation techniques, catalysis and others. One of the many areas of application of ionic liquids is sensors especially electrochemical sensors including ion-selective electrodes. In this case, the properties of ILs that are particularly useful include very good electrical conductivity, high electrochemical stability, good extraction properties, hydrophobic character and compatibility with other materials, e. g. polyvinyl chloride plasticizers or carbon nanomaterials. ILs were used as components of ion-selective membranes, both polymeric ones based on PVC and membranes in carbon paste electrodes. ILs performed various functions in these membranes, including lipophilic ionic additive, ionophore/ion exchanger, plasticizer, transducer media and matrix. They were also used as a component of the intermediate layer in solid contact ISEs. The last chapter presents examples of the use of ILs in reference electrodes. This review discusses the use of ionic liquids in ion-selective electrodes (ISEs) and reference electrodes over the last ten years.

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.

Chronopotentiometric sensors for antimicrobial peptide-based biosensing of Staphylococcus aureus.

Charged antimicrobial peptides can be used for direct potentiometric biosensing, but have never been explored. We report here a galvanostatically-controlled potentiometric sensor for antimicrobial peptide-based biosensing. Solid-state pulsed galvanostatic sensors that showed excellent stability under continuous galvanostatic polarization were prepared by utilizing reduced graphene oxide/poly (3,4-ethylenedioxythiophene): poly (4-styrenesulfonate) (rGO/PEDOT: PSS) as a solid contact. More importantly, the chronopotentiometric sensor can be made sensitive to antimicrobial peptides with intrinsic charge on demand via a current pulse. In this study, a positively charged antimicrobial peptide that can bind to Staphylococcus aureus with high affinity and good selectivity was designed as a model. Two arginine residues with positive charges were linked to the C-terminal of the peptide sequence to increase its potentiometric responses on the electrode. The bacteria binding-induced charge or charge density change of the antimicrobial peptide enables the direct chronopotentiometric detection of the target. Under the optimized conditions, the concentration of Staphylococcus aureus can be determined in the linear range 10-1.0 × 105 CFU mL-1 with a detection limit of 10 CFU mL-1. It is anticipated that such a chronopotentiometric sensing platform is readily adaptable to detect other bacteria by choosing the peptides.

A cathodically polarized PANI-based lead ion-selective electrode: achieving high stability with antibiofouling capabilities.

Solid-state contact ion-selective electrodes (SC-ISEs) are an efficacious means of monitoring heavy metal contamination. Instability of the electrode potential is a key factor limiting their development, with biofouling in real water samples posing a significant challenge to maintaining stability. Therefore, addressing biofouling is crucial for optimizing solid-state ion-selective electrodes. In this work, high stability and antibiofouling capability in a solid-state contact lead ion-selective electrode (SC-Pb2+-ISE) based on polyaniline (PANI) was achieved through cathodic polarization. Specifically, PANI played a dual role in the ion-selective membrane (ISM) as an ion-to-electron transducer and antifouling agent. Given the excellent electrochemical performance of PANI, the prepared electrode (GC/PANI-Pb2+-ISM) demonstrated a remarkable antibiofouling efficiency of 98.2% under a cathodic polarization of -0.2 V. Furthermore, a standard deviation of standard potential (Eθ) as low as ± 0.5 mV was realized successfully. The excellent chrono-potentiometric stability of 17.0 ± 2.9 µV/s was also demonstrated. The electrode maintained a Nernstian response slope of 30.7 ± 0.2 (R2 = 0.998) after applying a cathode potential (-0.2 V) for 30 min. The developed GC/PANI-Pb2+-ISM electrode is suitable for practical applications in real environmental water sample monitoring.

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

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

Sequestration of cyanide ions from aqueous medium by physio-chemically fabricated biochar of peels of banana and grape fruit in ecofriendly way.

Pakistan is an agricultural country producing plenty of fruits, like: mango, banana, apple, peaches, grapes, plums, variety of citrus fruits including lemon, grapefruit, and oranges. So far the peels of most of the fruits are usually wasted and not properly utilized anywhere. In this work, the peels of banana and grapefruit are converted into biochar by slow pyrolysis under controlled supply of air and used for sequestering cyanide ions from aqueous medium after chemical modification with ZnCl2 and sodium dodecyl sulfate (SDS). The modified biochar was characterized by various instrumental techniques, like: SEM, FTIR, TGA, and CHNS. Different parameters, like: time, temperature, pH, and dose of adsorbent affecting the adsorption of cyanide ions, onto prepared biochar were optimized and to understand the adsorption phenomenon, kinetic and thermodynamic studies were performed. Concentration of cyanide ions was estimated by employing standard ion selective electrode system and it is found that Sodium Dodecyl Sulfate treated biochar of banana peels shown more adsorption capacity, i.e.,: 17.080 mg/g as compared to all samples. Present work revealed that the biochar produced from the fruit waste has sufficient potential to eliminate trace quantities of cyanide from water, especially after treatment with sodium dodecyl sulfate.

An industrial area in Asian and African countries where mining is done using traditional techniques is the major cause of cyanide toxicity in wastewater streams. So, here chemically fabricated biochar made by peels of banana and grape fruit is employed for removal of cyanide ion for controlling aquatic pollution using local resources in green way. Favorable results indicated the feasibility of this process, which is cost effective, convenient, ecofriendly, and sustainable.

Application of Potentiometric and Electrophoretic Measurements to Evaluate the Reversibility of Adsorption of Divalent Ions from a Solution on Titanium Dioxide.

The adsorption of divalent ions on metal oxides is controlled by the pH of a solution. It is commonly assumed that this is a reversible process for pH changes. However, there are reports that the sorption of ions on oxides may not be reversible. To verify this, we used potentiometric titration, ion-selective electrodes (ISEs), and electrokinetic measurements to examine the reversibility of the adsorption of hydrogen ions and three metal ions (Ca2+, Cu2+, and Fe2+) on TiO2. The ferrous ion was used as a reference because its adsorption is entirely irreversible. The surface charge determined by potentiometric titration and the adsorption edges measured using ISE indicate that the adsorption of copper ions is reversible with changes in pH. In the case of calcium ions, the results suggest a certain degree of irreversibility. There are apparent differences in the electrokinetic potential data obtained during titration with base and acid, which suggests that the adsorption is irreversible. We have explained this contradiction by considering the complex and dynamic nature of electrophoretic mobility. In our opinion, potentiometric titration may be the simplest and most reliable method for assessing the reversibility of multivalent ion adsorption.

Formulation of Saxagliptin Oral Films: Optimization, Physicochemical Characterization, In-Vivo Assessment, and In-Vitro Real-Time Release Monitoring via a Novel Polyaniline Nanoparticles-Based Solid-Contact Screen Printed Ion-Selective Electrode.

Oral dispersible films have received broad interest due to fast drug absorption and no first-path metabolism, leading to high bioavailability and better patient compliance. Saxagliptin (SXG) is an antidiabetic drug that undergoes first-path metabolism, resulting in a less active metabolite, so the development of SXG oral dispersible films (SXG-ODFs) improves SXG bioavailability. The formula optimisation included a response surface experimental design and the impact of three formulation factors, the type and concentration of polymer and plasticiser concentration on in-vitro disintegration time and folding endurance. Two optimised SXG-ODFs prepared using either polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose were investigated. SXG-ODFs prepared with PVA demonstrated a superior rapid disintegration time, ranging from 17 to 890 s, with the fastest disintegration time recorded at 17 s. These short durations can be attributed to the hydrophilic nature of PVA, facilitating rapid hydration and disintegration upon contact with saliva. Additionally, PVA-based films displayed remarkable folding endurance, surpassing 200 folds without rupture, indicating flexibility and stability. The high tensile strength of PVA-based films further underscores their robust mechanical properties, with tensile strength values reaching up to 4.53 MPa. SXG exhibits a UV absorption wavelength of around 212 nm, posing challenges for traditional quantitative spectrophotometric analysis, so a polyaniline nanoparticles-based solid-contact screen-printed ion-selective electrode (SP-ISE) was employed for the determination of SXG release profile effectively in comparison to HPLC. SP-ISE showed a better real-time release profile of SXG-ODFs, and the optimised formula showed lower blood glucose levels than commercial tablets.

Point-of-care diagnostics for rapid determination of prostate cancer biomarker sarcosine: application of disposable potentiometric sensor based on oxide-conductive polymer nanocomposite.

One of the most important reasons for an increased mortality rate of cancer is late diagnosis. Point-of-care (POC) diagnostic sensors can provide rapid and cost-effective diagnosis and monitoring of cancer biomarkers. Portable, disposable, and sensitive sarcosine solid-contact ion-selective potentiometric sensors (SC-ISEs) were fabricated as POC analyzers for the rapid determination of the prostate cancer biomarker sarcosine. Tungsten trioxide nanoparticles (WO3 NPs), polyaniline nanoparticles (PANI NPs), and PANI-WO3 nanocomposite were used as ion-to-electron transducers on screen-printed sensors. WO3 NPs and PANI-WO3 nanocomposite have not been investigated before as ion-to-electron transducer layers in potentiometric SC sensors. The designated sensors were characterized using SEM, XRD, FTIR, UV-VIS spectroscopy, and EIS. The inclusion of WO3 and PANI in SC sensors enhanced the transduction at the interface between the screen-printed SC and the ion-selective membrane, offering lower potential drift, a longer lifetime, shorter response time, and better sensitivity. The proposed sarcosine sensors exhibited Nernstian slopes over linear response ranges 10-3-10-7 M, 10-3-10-8 M, 10-5-10-9 M, and 10-7-10-12 M for control, WO3 NPs, PANI NPs, and PANI-WO3 nanocomposite-based sensors, respectively. From a comparative point of view between the four sensors, PANI-WO3 nanocomposite inclusion offered the lowest potential drift (0.5 mV h-1), the longest lifetime (4 months), and the best LOD (9.95 × 10-13 M). The proposed sensors were successfully applied to determine sarcosine as a potential prostate cancer biomarker in urine without prior sample treatment steps. The WHO ASSURED criteria for point-of-care diagnostics are met by the proposed sensors.

All-solid-state potentiometric salicylic acid sensor for in-situ measurement of plant.

Using PEDOT as the conductive polymer, an innovative small-scale sensor for directly measuring salicylate ions in plants was developed, which avoided the complicated sample pretreatment of traditional analytical methods and realized the rapid detection of salicylic acid. The results demonstrate that this all-solid-state potentiometric salicylic acid sensor is easy to miniaturize, has a longer lifetime (≥1 month), is more robust, and can be directly used for the detection of salicylate ions in real samples without any additional pretreatment. The developed sensor has a good Nernst slope (63.6 ± 0.7 mV/decade), the linear range is 10-2 ~ 10-6 M, and the detection limit can reach (2.8 × 10-7 M). The selectivity, reproducibility, and stability of the sensor were evaluated. The sensor can perform stable, sensitive, and accurate in situ measurement of salicylic acid in plants, and it is an excellent tool for determining salicylic acid ions in plants in vivo.

Solid-state ion-selective electrodes for the first potentiometric determination of the anti-COVID 19 drug Remdesivir in human plasma; A comparative study.

Establishing sensitive and targeted analytical methodologies for drug identification in biological fluids as well as screening of treatments that can counteract the most severe COVID-19 infection-related side effects are of utmost importance. Here, first attempts have been made for determination of the anti-COVID drug Remdesivir (RDS) in human plasma using four potentiometric sensors. Calixarene-8 (CX8) was used as an ionophore applied to the first electrode (Sensor I). The second had a layer of dispersed graphene nanocomposite coating (Sensor II). (Sensor III) was fabricated using nanoparticles of polyaniline (PANI) as ion-to-electron transducer. A reverse-phase polymerization using polyvinylpyrrolidone (PVP) was employed to create a graphene-polyaniline (G/PANI) nanocomposite electrode (Sensor IV). Surface morphology was confirmed by Scanning Electron Microscope (SEM). UV absorption spectra and Fourier Transform Ion Spectrophotometry (FTIR) also supported their structural characterization. The impact of graphene and polyaniline integration on the functionality and durability of the manufactured sensors was examined using the water layer test and signal drift. In the ranges of concentration of 10-7 to 10-2 mol/L and 10-7 to 10-3, sensors II & IV exhibited linear responses; respectively while sensors I & III displayed linearity within 10-6 to 10-2 mol/L. The target drug was easily detectable using LOD down to 100 nmol/L. The developed sensors satisfactorily offered sensitive, stable, selective and accurate estimate of Remdesivir (RDS) in its pharmaceutical formulation as well as spiked human plasma with recoveries ranging from 91.02 to 95.76 % with average standard deviations less than 1.85. The suggested procedure was approved in accordance with ICH recommendations.

Large-scale fabrication of ion-selective electrodes for simultaneous detection of Na+, K+, and Ca2+ in biofluids using a smartphone-based potentiometric sensing platform.

A significant bottleneck exists for mass-production of ion-selective electrodes despite recent developments in manufacturing technologies. Here, we present a fully-automated system for large-scale production of ISEs. Three materials, including polyvinyl chloride, polyethylene terephthalate and polyimide, were used as substrates for fabricating ion-selective electrodes (ISEs) using stencil printing, screen-printing and laser engraving, respectively. We compared sensitivities of the ISEs to determine the best material for the fabrication process of the ISEs. The electrode surfaces were modified with various carbon nanomaterials including multi-walled carbon nanotubes, graphene, carbon black, and their mixed suspensions as the intermediate layer to enhance sensitivities of the electrodes. An automated 3D-printed robot was used for the drop-cast procedure during ISE fabrication to eliminate manual steps. The sensor array was optimized, and the detection limits were 10-5 M, 10-5 M and 10-4 M for detection of K+, Na+ and Ca2+ ions, respectively. The sensor array integrated with a portable wireless potentiometer was used to detect K+, Na+ and Ca2+ in real urine and simulated sweat samples and results obtained were in agreement with ICP-OES with good recoveries. The developed sensing platform offers low-cost detection of electrolytes for point-of-care applications.

A Simple Reversed Iontophoresis-Based Sensor to Enable In Vivo Multiplexed Measurement of Plant Biomarkers Using Screen-Printed Electrodes.

The direct quantification of plant biomarkers in sap is crucial to enhancing crop production. However, current approaches are inaccurate, involving the measurement of non-specific parameters such as colour intensity of leaves, or requiring highly invasive processes for the extraction of sap. In addition, these methods rely on bulky and expensive equipment, and they are time-consuming. The present work reports for the first time a low-cost sensing device that can be used for the simultaneous determination of sap K+ and pH in living plants by means of reverse iontophoresis. A screen-printed electrode was modified by deposition of a K+-selective membrane, achieving a super-Nernstian sensitivity of 70 mV Log[K+]−1 and a limit of detection within the micromolar level. In addition, the cathode material of the reverse iontophoresis device was modified by electrodeposition of RuOx particles. This electrode could be used for the direct extraction of ions from plant leaves and the amperometric determination of pH within the physiological range (pH 3−8), triggered by the selective reaction of RuOx with H+. A portable and low-cost (<£60) microcontroller-based device was additionally designed to enable its use in low-resource settings. The applicability of this system was demonstrated by measuring the changes in concentration of K+ and pH in tomato plants before and after watering with deionised water. These results represent a step forward in the design of affordable and non-invasive devices for the monitoring of key biomarkers in plants, with a plethora of applications in smart farming and precision agriculture among others.

A Novel Polymeric Membrane Sensor for Chlorhexidine Determination.

In the present work, potentiometric sensors with polymer membranes used for chlorhexidine (CHXD) determination were developed. The polymer membranes were plasticized with bis(2-ethylheksyl)sebacate (DOS) or 2-nitrophenyloctyl ether (o-NPOE). The active compounds used in the membrane were cyclodextrins, crown ethers, and ion exchangers. The best-constructed electrode was based on neutral heptakis(2,3,6-tri-O-benzoyl)-ß-cyclodextrin with lipophilic salt (KTpClBP)-potassium tetrakis(4-chlorophenyl) borate-dissolved in plasticizer, DOS. The presented electrode is characterized by an average cationic slope of 30.9 ± 2.9 mV decade-1 within a linear range of 1 × 10-6 to 1 × 10-3 mol × L-1, while the value of the correlation coefficient is 0.9970 ± 0.0026. The response time was about 5 s when increasing the sample concentration and about 10 s when diluting the sample. The electrode potential is independent of the pH within a range of 4.0-9.5. The polymeric membrane sensor was successfully applied for assays of chlorhexidine digluconate in pure samples and pharmaceutical samples. The relative error from three replicate measurements was determined to be 1.1%. and the accuracy was RSD = 0.3-1.1%.

Ion fluxes Involved in the Adaptation of the Estuarine Diatom Coscinodiscus centralis Ehrenberg to Salinity Stress.

Although estuarine diatoms have a wide range of salt tolerance, they are often severely stressed by elevated salt concentrations. It remains poorly understood how estuarine diatoms maintain ionic homeostasis under high-salinity conditions. Using a scanning ion-selective electrode technique, this study determined the fluxes of H+, Na+, and K+ involved in the acclimatization of the estuarine diatom Coscinodiscus centralis Ehrenberg after an elevation in salinity from 15 psu to 35 psu. The C. centralis cells exhibited marked H+ effluxes after a transient treatment (TT, 30 min) and short-term treatment (ST, 24 h). However, a drastic shift of H+ efflux toward an influx was induced in the long-term treatment (LT, 10 days). The Na+ flux under TT, ST, and LT salinity conditions was found to accelerate the Na+ efflux. More pronounced effects were observed under the ST and LT salinity conditions compared to the TT salinity condition. The K+ influx showed a significant increase under the LT salinity condition. However, the salinity-induced Na+/H+ exchange in the estuarine diatom was inhibited by amiloride and sodium orthovanadate. These results indicate that the Na+ extrusion in salt-stressed cells is mainly the result of an active Na+/H+ antiport across the plasma membrane. The pattern of ion fluxes under the TT and ST salinity conditions were different from those under the LT salinity conditions, suggesting an incomplete regulation of the acclimation process in the estuarine diatom under short-term salinity stress.

Preparation of ß-Cyclodextrin Functionalized Platform for Monitoring Changes in Potassium Content in Perspiration.

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 ß-cyclodextrin functionalized reduced graphene oxide (ß-CD-RGO) for selective K+ quantification in sweat. The ß-CD prevents the aggregation of RGO sheets while also providing selective binding sites for K+ capture. Electrodes were fabricated by screen printing the ß-CD-RGO ink onto conductive carbon substrates. Material characterization confirmed the successful functionalization of RGO with ß-CD. Cyclic voltammetry (CV) showed enhanced electrochemical behavior for ß-CD-RGO-printed electrodes compared with bare carbon and RGO. Sensor optimization resulted in a formulation with 30% ß-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 ß-CD-RGO inks enables the scalable fabrication of wearable sensors for sweat potassium detection.

A Multi-Pumping Gradient Calibration Module for Potentiometric Determination of Nitrate in Surface Water.

The novel, automated, multi-pumping flow system (MPFS) for online calibration and determination of nitrate in surface water is presented for the first time. The system was equipped with micropumps of three different nominal volumes (10, 20, and 50 µL). As a result, it was possible to prepare from one standard, directly in a flow system, up to seven standard solutions. Determination of nitrate was conducted in stop-flow conditions and is based on a commercially available ion selective electrode (ISE) application. It was found that the linearity and slope of the calibration graphs depend mainly on the characteristics of the ISE. The obtained results were very repeatable, owing to the high precision of the micro-pumps used. The R.S.D. for the stroke volume of each micro-pump was below 1%. The accuracy of the method was checked through determination of nitrate in surface water samples. The obtained results were compared with those of the reference method (photometric Hach cuvette tests). It was found that, at a 96% confidence level, the difference between the results obtained by the proposed method and the reference method was statistically insignificant. The accuracy of the method was confirmed through the determination of nitrate in Certified Reference Material. The relative deviation (R.D.) of the measured and the certified concentrations was 5%.

Green potentiometric electrode for determination of salbutamol in biological samples.

Clinical drug analyses and identification of pharmaceuticals in biological samples are highly crucial for therapeutic drug monitoring, pharmacokinetic studies, and screening of illicit drugs. Various analytical tools, such as potentiometric electrodes, are used to conduct these investigations. These potentiometric electrodes are superior to other techniques in terms of greenness and cost efficacy, and thus present a good alternative for researchers. In this study, we develop an advanced electrode for the in-situ monitoring of salbutamol in plasma, this electrode was synthesized using multiwalled carbon nanotubes (MWCNT) as hydrophobic conductive substance and copper oxide nanoparticle (CuO NP) as a surface modifier, the developed electrode was compared to traditional liquid contact electrode as well as solid contact electrode and proved its superiority. The use of MWCNT improved the stability of the electrode via preventing the formation of this water layer and the CuO NP improved the sensitivity due to its high surface area and rich electronic properties. CuO NP modified electrode was used for the determination of salbutamol with a Nernstian slope of 57.4 over a linearity range of range 1.0 × 10-7- 1.0 × 10-2 M, and a detection limit of 4.0 × 10-7 M. The proposed electrode was effectively applied for the determination of the cited drug in rat plasma without interference and compared with chromatographic reported method. The proposed method is economic as it has a low sample analysis cost, time saving and needs fewer manipulation steps and a simple convenient device. It also proved to be a greener method when compared with chromatographic methods using an eco-scale metric system.

Case report: Salicylate intoxication can present with a normal anion gap metabolic acidosis depending on method used for measuring chloride.

Severe salicylate intoxication usually presents with a high anion gap metabolic acidosis. We describe a patient with severe salicylate intoxication who presented with a surprisingly normal anion gap metabolic acidosis. Initial salicylate level was 594 mg/L (therapeutic range 50-300 mg/L). In this case, the anion gap was normal due to a falsely elevated chloride concentration measured using a direct ion-selective electrode (ISE; ABL90-flex). Since earlier case reports have shown that salicylate ions can interfere with chloride measurement using different ISEs, available samples were reanalysed using an indirect ISE (Roche Cobas 8000), in which salicylate levels up to 1000 mg/L were found to cause no significant interference. With this method, chloride concentration was found to be 115 instead of 122 mmol/L, leading to the expected elevated anion gap. We performed a spike experiment to investigate the impact of different salicylate levels and bicarbonate concentrations on the measured chloride concentration for both methods. This experiment showed that the difference between chloride concentrations was mainly explained by interference with bicarbonate. It is important for clinicians to be aware of this possible interference, since a high anion gap metabolic acidosis can be a clue to suspect salicylate poisoning and early recognition and appropriate treatment is important. The patient was successfully treated with haemodialysis and no rebound toxicity was observed.