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Abstract Recently, drug-controlled release nanotechnology has gained special attention in biomedicine. This work focuses on developing novel electrospun polymeric nanofibers (NFs) for buccal delivery of VEN to avoid the hepatic metabolism and enzymatic degradation in the GIT and develop an effective control of drug release. The optimized NFs were obtained by blending polylactic acid (PLA), and poly (ɛ-caprolactone) (PCL) fixed at a ratio of 1:1. It was characterized for morphology, drug-loading, FTIR, XRD, DSC, and in vitro drug release. Ex vivo permeability of the blend NFs was assessed using chicken pouch mucosa compared to VEN suspension, followed by histopathological examination. Further, the cytotoxic effect in three different cell lines using WST-1 assay. SEM morphologies refer to defect-free uniform NFs of PLA, PCL, and PLA/PCL mats. These fibers had a diameter ranging from 200 to 500 nm. The physico-thermal characterization of NFs depicted that the drug was successfully loaded and in an amorphous state in the PLA/PCL NFs. In vitro release of NFs substantiated a bi-phasic profile with an initial burst release of about 30% in the initial 0.5 h and a prolonged cumulative release pattern that reached 80% over 96 h following a non-Fickian diffusion mechanism. Ex vivo permeation emphasizes the major enhancement of the sustained drug release and the noticeable decrease in the permeability of the drug from NFs. Cytotoxicity data found that IC50 of VEN alone was 217.55 μg/mL, then VEN-NFs recorded an IC50 value of 250.62 μg/mL, and plain NFs showed the lowest toxicity and IC50 440.48 μg/mL in oral epithelial cells (OEC). Histopathology and cell toxicity studies demonstrated the preserved mucosal architecture and the preclinical safety. The developed PLA/PCL NFs can be promising drug carriers to introduce a step-change in improved psychiatric treatment healthcare.

The continuous production and widespread applications of synthetic plastics and their waste present immense environmental challenges and damage living systems. Microplastics (MPs) have become of great concern in various ecosystems due to their high stability and decomposition into smaller fragments such as nano-plastics (NPs). Nevertheless, MPs and NPs can be removed from the environment using several physical, chemical, and microbiological methods. This study presents a comprehensive narrative literature review, which aims to explore the various types of MPs and NPs, their sources, fate, toxicity, and impact on human health and environment. To achieve this aim, the study employed a comprehensive literature review methodology. In addition, it summarizes various methods of sample collection and analysis techniques. Remediation strategies for MPs and NPs removal are assessed and compared. Furthermore, it highlights interlinkages between the sustainable development goals (SDGs)—specifically SDG 14—and plastic pollution. Overall, priority for research and development in the field of MPs and NPs impacts on ecological ecosystems is a must as this will enable the development of scientific polices driven by global collaboration and governance which in turn will develop tools and methodologies that measure the impacts and risk of plastic pollution.

Global warming and climate changes are among the biggest modern-day environmental problems, the main factor causing these problems is the greenhouse gas effect. The increased concentration of carbon dioxide in the atmosphere resulted in capturing increased amounts of reflected sunlight, causing serious acute and chronic environmental problems. The concentration of carbon dioxide in the atmosphere reached 421 ppm in 2022 as compared to 280 in the 1800s, this increase is attributed to the increased carbon dioxide emissions from the industrial revolution. The release of carbon dioxide into the atmosphere can be minimized by practicing carbon capture utilization and storage methods. Carbon capture utilization and storage (CCUS) has four major methods, namely, pre-combustion, post-combustion, oxyfuel combustion, and direct air capture. It has been reported that applying CCUS can capture up to 95% of the produced carbon dioxide in running power plants. However, a reported cost penalty and efficiency decrease hinder the wide applicability of CCUS. Advancements in the CCSU were made in increasing the efficiency and decreasing the cost of the sorbents. In this review, we highlight the recent developments in utilizing both physical and chemical sorbents to capture carbon. This includes amine-based sorbents, blended absorbents, ionic liquids, metal-organic framework (MOF) adsorbents, zeolites, mesoporous silica materials, alkali-metal adsorbents, carbonaceous materials, and metal oxide/metal oxide-based materials. In addition, a comparison between recently proposed kinetic and thermodynamic models was also introduced. It was concluded from the published studies that amine-based sorbents are considered assuperior carbon-capturing materials, which is attributed to their high stability, multifunctionality, rapid capture, and ability to achieve large sorption capacities. However, more work must be done to reduce their cost as it can be regarded as their main drawback.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide worldwide. However, its residues in agricultural products are extremely harmful to human health and to the environment in soil and water. Previous methods for determining 2,4-D in water and soil samples are expensive, cumbersome, and not highly selective. In this study, we developed a novel disposal sensor based on screen-printed electrodes (SPEs) for detecting 2,4-D in wastewater and soil samples. The SPEs were modified with conductive polyaniline (PANI) layer and polyvinyl chloride (PVC) membrane loaded with molecularly printed polymer (MIP). The MIP particles were prepared using 2,4-D as template, methacrylic acid (MAA) as monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker, and benzoyl peroxide as initiator. The best sensor shows a dynamic concentration range of 10−2 to 10−7 M 2,4-D, a detection limit (LOD) of 3.6 × 10−7 M, Nernst slope (response) of 29.9 mV/decade, and high selectivity over other interfering species previously reported in the literature. The sensors also achieved a short response time of 25 s, high reversibility, and a lifetime of over 2 weeks. The developed sensors were successfully used for determining 2,4-D in real wastewater and soil samples with high accuracy and precision.

Using single-walled carbon nanotubes (SWCNTs) as an ion-to-electron transducer, a novel disposable all-solid-state desvenlafaxine-selective electrode based on a screen-printed carbon paste electrode was created. SWCNTs were put onto the carbon-paste electrode area, which was protected by a poly (vinyl chloride) (PVC) membrane with a desvenlafaxine-imprinted polymer serving as a recognition receptor. Electrochemical impedance spectroscopy and chronopotentiometric techniques were used to examine the electrochemical characteristics of the SWCNTs/PVC coating on the carbon screen-printed electrode. The electrode displayed a 57.2 ± 0.8 mV/decade near-Nernstian slope with a 2.0 × 10−6 M detection limit. In 10 mM phosphate buffer, pH 6, the ODV-selective electrodes displayed a quick reaction (5 s) and outstanding stability, repeatability, and reproducibility. The usefulness of electrodes was demonstrated in samples of ODV-containing pharmaceutical products and human urine. These electrodes have the potential to be mass produced and employed as disposable sensors for on-site testing, since they are quick, practical, and inexpensive.

Caffeine is a psychoactive drug that is administered as a class II psychotropic substance. It is also considered a component of analgesics and cold medicines. Excessive intake of caffeine may lead to severe health damage or drug addiction problems. The assessment of normal caffeine consumption from abusive use is not conclusive, and the cut-off value for biological samples has not been established. Herein, new cost-effective and robust all-solid-state platforms based on potentiometric transduction were fabricated and successfully utilized for caffeine assessment. The platforms were modified with reduced graphene oxide (rGO). Tailored caffeine-imprinted polymeric beads (MIPs) based on methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were prepared, characterized, and used as recognition receptors in the presented potentiometric sensing devices. In 50 mM MES buffer, the sensors exhibited a slope response of 51.2 ± 0.9 mV/decade (n = 6, R2 = 0.997) over the linear range of 4.5 × 10−6–1.0 × 10−3 M with a detection limit of 3.0 × 10−6 M. They exhibited fast detection of caffeinium ions with less than 5 s response time (

Novel cost-effective screen-printed potentiometric platforms for simple, fast, and accurate assessment of Fluoxetine (FLX) were designed and characterized. The potentiometric platforms integrate both the FLX sensor and the reference Ag/AgCl electrode. The sensors were based on the use of 4′-nitrobenzo-15-crown-5 (ionophore I), dibenzo-18-crown-6 (ionophore II), and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) (ionophore III) as neutral carriers within a plasticized PVC matrix. Multiwalled carbon nanotubes (MWCNTs) were used as a lipophilic ion-to-electron transducing material and sodium tetrakis [3,5-bis(trifluoromethyl)phenyl] borate (NaTFPB) was used as an anionic excluder. The presented platforms revealed near-Nernstian potentiometric response with slopes of 56.2 ± 0.8, 56.3 ± 1.7 and 64.4 ± 0.2 mV/decade and detection limits of 5.2 × 10−6, 4.7 × 10−6 and 2.0 × 10−7 M in 10 mM Tris buffer solution, pH 7 for sensors based on ionophore I, II, and III, respectively. All measurements were carried out in 10 mM tris buffer solution at pH 7.0. The interfacial capacitance before and after insertion of the MWCNTs layer was evaluated for the presented sensors using the reverse-current chronopotentiometry. The sensors were introduced for successful determination of FLX drug in different pharmaceutical dosage forms. The results were compared with those obtained by the standard HPLC method. Recovery values were calculated after spiking fixed concentrations of FLX in different serum samples. The presented platforms can be potentially manufacturable at large scales and provide a portable, rapid, disposable, and cost-effective analytical tool for measuring FLX.

In recent times, the application of the use of ion-selective electrodes has expanded in the field of pharmaceutical analyses due to their distinction from other sensors in their high selectivity and low cost of measurement, in addition to their high measurement sensitivity. Cost-effective, reliable, and robust all-solid-state potentiometric selective electrodes were designed, characterized, and successfully used for pholcodine determination. The design of the sensor device was based on the use of a screen-printed electrode modified with multiwalled carbon nanotubes (MWCNTs) as a solid-contact transducer. Tailored pholcodine (PHO) molecularly imprinted polymers (MIPs) were prepared, characterized, and used as sensory receptors in the presented potentiometric sensing devices. The sensors exhibited a sensitivity of 31.6 ± 0.5 mV/decade (n = 5, R2 = 0.9980) over the linear range of 5.5 × 10−6 M with a detection limit of 2.5 × 10−7 M. Real serum samples in addition to pharmaceutical formulations containing PHO were analyzed, and the results were compared with those obtained by the conventional standard liquid chromatographic approach. The presented analytical device showed an outstanding efficiency for fast, direct, and low-cost assessment of pholcodine levels in different matrices.

Novel potentiometric sensors for selective screening of sulfamethazine (SMZ) in pharmaceutical preparations and milk samples are reported. The sensor membranes were made from PVC matrix doped with magnesium(II)-, manganese(II)- and dichlorotin (IV)-phthalocyanines as ionophores and aliquat-336 and nitron/SMZ ion-pair complex as ion exchangers. These sensors revealed fast, stable and near-Nernstian anionic response for the singly charged sulfamethazine anion over the concentration range 10-2 - 10-5 M. The sensors exhibited good selectivity towards SMZ over most known anions, excipients and diluents commonly added in drug preparations. Validation of the proposed methods was demonstrated via evaluating the detection limit, linear response range, accuracy, precision (within-day repeatability) and between-day-variability. The sensors are easily interfaced with a double channel flow injection system and used for continuous monitoring of SMZ in drug formulations, spiked milk samples and biological tissues. The method offers the advantages of design simplicity, results accuracy, and automation feasibility.

All-solid-state potentiometric sensors have attracted great attention over other types of potentiometric sensors due to their outstanding properties such as enhanced portability, simplicity of handling, affordability and flexibility. Herein, a novel solid-contact ion-selective electrode (SC-ISE) based on poly(3,4-ethylenedioxythiophene) (PEDOT) as the ion-to-electron transducer was designed and characterized for rapid detection of harmine. The harmine-sensing membrane was based on the use of synthesized imprinted bio-mimics as a selective material for this recognition. The imprinted receptors were synthesized using acrylamide (AA) and ethylene glycol dimethacrylate (EGDMA) as functional monomer and cross-linker, respectively. The polymerization process was carried out at 70 °C in the presence of dibenzoyl peroxide (DBO) as an initiator. The sensing membrane in addition to the solid-contact layer was applied to a glassy-carbon disc as an electronic conductor. All performance characteristics of the presented electrode in terms of linearity, detection limit, pH range, response time and selectivity were evaluated. The sensor revealed a wide linearity over the range 2.0 × 10−7–1.0 × 10−2 M, with a detection limit of 0.02 µg/mL and a sensitivity slope of 59.2 ± 0.8 mV/hamine concentration decade. A 40 mM Britton–Robinson (BR) buffer solution at pH of 6 was used for all harmine measurements. The electrode showed good selectivity towards harmine over other common interfering ions, and maintained a stable electrochemical response over two weeks. After applying the validation requirements, the proposed method revealed good performance characteristics. Method precision, accuracy, bias, trueness, repeatability, reproducibility, and uncertainty were also evaluated. These analytical capabilities support the fast and direct assessment of harmine in different urine specimens. The analytical results were compared with the standard liquid chromatographic method. The results obtained demonstrated that PEDOT/PSS was a promising solid-contact ion-to-electron transducer material in the development of harmine-ISE. The electrodes manifested enhanced stability and low cost, which provides a wide number of potential applications for pharmaceutical and forensic analysis.

Solid-contact ion-selective electrodes (SC-ISEs) have shown great potential for routine and portable ion detection. The introduction of nanomaterials as ion-to-electron transducers and the adoption of different performance-enhancement strategies have significantly promoted the development of SC-ISEs. Herein, new solid-contact ion-selective electrodes, along with the implementation of multiwalled carbon nanotubes (MWCNTs) as ion-to-electron transducers and potassium tetrakis (p-chlorophenyl) borate (KTpClB) as lipophilic ionic additives, were presented for the detection of isoproturon (IPU) and diuron (DU) herbicides. Molecularly imprinted polymers (MIPs), with special molecule recognition properties for isoproturon (IPU) and diuron (DU), were prepared, characterized, and introduced as sensory recognition materials in the presented electrodes. Sensors revealed a near-Nernstian response for both isoproturon (IPU) and diuron (DU) with slopes of 53.1 ± 1.2 (r2 = 0.997) and 57.2 ± 0.3 (r2 = 0.998) over the linear ranges of 2.2 × 10−6–1.0 × 10−3 M and 3.2 × 10−6–1.0 × 10−3 M with detection limits of 8.3 × 10−7 and 1.4 × 10−6 M, respectively. The response time of the presented sensors was found to be

Novel reliable and cost-effective potentiometric screen-printed sensors for free bilirubin (BR) detection were presented. The sensors were fabricated using ordered mesoporous carbon (OMC) as an ion-to-electron transducer. The ion-association complex [Ni(bphen)3]2+[BR]2− was utilized as a sensory recognition material in the plasticized Polyvinyl Chloride (PVC) membrane. The membrane was drop-casted on the OMC layer, which is attached on a carbon conductor (2-mm diameter). In a 50 mM phosphate solution of pH 8.5, the electrodes offered a Nernstian slope of −26.8 ± 1.1 (r2 = 0.9997) mV/decade with a range of linearity 1.0 × 10−6–1 × 10−2 M towards free bilirubin with a detection limit 8.8 × 10−7 M (0.52 µg/mL). The presented sensors offered good features in terms of reliability, ease of design, high potential stability, high specificity and good accuracy and precision. Chronopotentiometric and electrochemical impedance spectrometric measurements were used for short-term potential stability and interfacial capacitance calculations. The sensors were used for the determination of free bilirubin in biological fluids. The data obtained are fairly well consistent with those obtained by the reference spectophotometric method. Based on the interaction of free BR with albumin (1:1), the sensors were also utilized for the assessment of albumin in human serum.

Reliable, cost-effective, and robust screen-printed sensors were constructed and presented for Ca2+ ions determination. The sensors were based on the use of bilirubin (1,3,6,7-tetramethyl-4,5- dicarboxyethy-2,8-divinyl-(b-13)-dihydrobilenone) as a recognition sensory material in plasticized poly (vinyl chloride) (PVC) membranes. Polypyrrol (PPY) and graphene oxide (GO) were used as ion-to-electron transducers, where the effects of anionic excluder, pH, and selectivity were investigated. In a 50 mM tris buffer solution of pH 5, the electrodes offered a potential response for Ca2+ ions with a near-Nernstian slopes of 38.1 ± 0.4 (r2 = 0.996) and 31.1 ± 0.6 (r2 = 0.999), detection limits 3.8 × 10−6 (0.152 μg/mL) and 2.3 × 10−7 M (8.0 ng/mL), and linear concentration ranges of 7.0 × 10−6–1.0 × 10−2 (400–0.28 μg/mL) and 7.0 × 10−7–1.0 × 10−2 M (400–0.028 μg/mL) for sensors based on PPY and GO, respectively. Both sensors revealed stable potentiometric responses with excellent reproducibility and enhanced selectivity over a number of most common metal ions, such as Na+, K+, Li+, NH4+, Fe2+, Mg2+, and Ba2+. Impedance spectroscopy and chronopotentiometric techniques were used for evaluating the potential drift and the interfacial sensor capacitance. The proposed sensors offered the advantages of simple design, ability of miniaturization, good potential stability, and cost-effectiveness. The developed electrodes were applied successfully to Ca2+ ion assessment in different pharmaceutical products, baby-food formulations, and human blood samples. The results obtained were compared with data obtained by atomic absorption spectrometry (AAS).

A new validated method based on potentiometric transduction for bispyribac herbicide assessment in commercial formulations, rice and wastewater samples is fabricated and characterized. Sensors are based in terms of their fabrication on tridodecyl methyl ammonium chloride (TDMAC) as recognition material. TDMAC was plasticized in a poly (vinyl chloride) (PVC) matrix to prepare the membrane. Under static modes of operation, the sensors revealed a Nernstian anionic slope of −63.6 ± 0.7 mV/decade within a linear range of 9.1 × 10−6–1.0 × 10−2 in 50 mM phosphate buffer solution (PBS), pH7. The detection limit was 6.0 × 10−6 M. The sensor was successfully introduced in a flow-stream system revealing a Nernstian response of −53.8 ± 1.3 mV/decade over a linear range of 2 × 10−4–1.0 × 10−2 M and lower detection limit of 5.6 × 10⁻⁵ M. The sampling rate was calculated to be (~42 sample/h). Validation of the assay method is presented in detail including accuracy, trueness, bias, between-day variability and within-day variability, and good performance characteristics of the method are obtained. The presented method was successfully introduced to bispyribac determination in different complex matrices such as commercial bispyribac sodium known as (Nominee-kz, 3% soluble liquid (SL)), rice samples and agricultural wastewater samples. The samples were analyzed successfully under both static and hydrodynamic modes of operation. The results obtained were in a good agreement with those obtained by the liquid chromatographic method.

Herein, a novel validated potentiometric method is presented for the first time for citicoline determination. The method is based on measuring the potential using new constructed citicoline electrodes. The electrodes are based on the use of citicolinium/phosphomolybdate [Cit]2[PM] (sensor I) and citicolinium/tetraphenylborate [Cit][TPB] (sensor II) ion association complexes. These sensory materials were dispersed in plasticized polyvinyl chloride (PVC) polymeric membranes. The sensors revealed a Nernstian response with the slopes 55.9 ± 1.8(r2 = 0.9994) and 51.8 ± 0.9 (r2 = 0.9991) mV/decade over a linearity range of 6.3 × 10−6–1.0 × 10−3 and 1.0 × 10−5–1.0 × 10−3 M and detection limits of 3.16 × 10−6 and 7.1 × 10−6 M for sensors I and II, respectively. To ensure the existence of monovalent citicoline, all measurements were performed in 50 mM acetate buffer at pH 3.5. All presented electrodes showed good performance characteristics such as rapid response, good selectivity, high potential-stability and long life-span. Method verification and validation in terms of response linearity, quantification limit, accuracy, bias, trueness, robustness, within-day variability and between-days variability were evaluated. The method was introduced for citicoline determination in different pharmaceutical formulations and compared with the standard high performance liquid chromatography (HPLC) method.

Novel potentiometric devices “ion-selective electrodes (ISEs)” were designed and characterized for the detection of 17β-estradiol (EST) hormone. The selective membranes were based on the use of man-tailored biomimics (i.e., molecularly imprinted polymers (MIPs)) as recognition ionophores. The synthesized MIPs include a functional monomer (methacrylic acid (MAA)) and a cross-linker (ethylene glycol dimethacrylic acid (EGDMA)) in their preparation. Changes in the membrane potential induced by the dissociated 17β-estradiol were investigated in 50 mM CO32−/HCO3− buffer solution at pH 10.5. The ion-selective electrodes (ISEs) exhibited fast response and good sensitivity towards 17β-estradiol with a limit of detection 1.5 µM over a linear range starts from 2.5 µM with an anionic response of 61.2 ± 1.2 mV/decade. The selectivity pattern of the proposed ISEs was also evaluated and revealed an enhanced selectivity towards EST over several phenolic compounds. Advantages revealed by the presented sensor (i.e., wide range of assay, enhanced accuracy and precision, low limit of detection, good selectivity, long-term potential stability, rapid response and long life-span and absence of any sample pretreatment steps) suggest its use in routine quality control/quality assurance tests. They were successfully applied to estradiol determination in biological fluids and in different pharmaceutical preparations collected from the local market.

A simple potentiometric sensor is described for accurate, precise, and rapid determination of sulfite additives in beverages. The sensor is based on the use of cobalt phthalocyanine as a recognition material, dispersed in a plasticized poly(vinyl chloride) matrix membrane. o-Nitrophenyl octyl ether (o-NPOE) as a membrane solvent and tri-dodecylmethyl- ammonium chloride (TDMAC) as ion discriminators are used as membrane additives. Under the optimized conditions, sulfite ion is accurately and precisely measured under batch and flow injection modes of analysis. The sensor exhibits fast and linear response for 1.0 × 10−2–1.0 × 10−6 M (800–0.08 µg/mL) and 1.0 × 10−1–5.0 × 10−5 M (8000–4 µg/mL) sulfite with Nernstian slopes of −27.4 ± 0.3 and −23.7 ± 0.6 mV/concentration decade under static and hydrodynamic modes of operation, respectively. Results in good agreement with the standard iodometric method are obtained.Validation of the assay method is examined in details including precision, accuracy, bias, trueness, repeatability, reproducibility, and uncertainty and good performance characteristics of the method are obtained. The sensor response is stable over the pH range of 5 to 7 without any significant interference from most common anions. The advantages offered by the proposed sensor (i.e., wide range of assay, high accuracy and precision, low detection limit, reasonable selectivity, long term response stability, fast response, and long life span and absence of any sample pretreatment steps) suggest its use in the quality control/quality assurance routine tests in beverages industries, toxicological laboratories and by inspection authorities.

A simple, rapid and easy method is proposed for the detection of a cytostatic therapeutic drug, cytarabine, in real samples. The method is based on potentiometric transduction using prepared and characterized new ion-selective electrodes for cytarabine. The electrodes were integrated with novel man-tailored imprinted polymers and used as a sensory element for recognition. The electrodes revealed a remarkable potentiometric response for cytarabine over the linearity range 1.0 × 10−6–1.0 × 10−3 M at pH 2.8–4 with a detection limit of 5.5 × 10−7 M. The potentiometric response was near-Nernstian, with average slopes of 52.3 ± 1.2 mV/decade. The effect of lipophilic salts and plasticizer types on the potentiometric response was also examined. The electrodes exhibited an enhanced selectivity towards cytarabine over various foreign common ions. Validation and verification of the presented assay method are demonstrated by evaluating the method ruggedness and calculating the detection limit, range of linearity, accuracy (trueness), precision, repeatability (within-day) and reproducibility (between-days). The proposed ion-selective electrodes revealed good performance characteristics and possible application of these electrodes for cytarabine monitoring in different matrices. The electrodes are successfully applied to cytarabine determination in spiked biological fluid samples and in pharmaceutical formulations.

Copper ferrite nano-particles (CuFe2O4) were synthesized, characterized, modified with polyaniline to form CuFe2O4/PANI nano-composite. They were used as new adsorbents for the removal of the hazardous mercuric ions from aqueous solutions. High resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Brunauer–Emmett–Teller (BET) were used for the characterization of the synthesized CuFe2O4 nano-particles (NPs) in presence and absence of PANI nano-composite. The synthesized CuFe2O4NPs were of spherical shape with an average size of 10.8 nm. XRD analysis displayed crystal peaks for CuFe2O4NPs and amorphous peaks CuFe2O4/PANI nano-composite due to the existence of polyaniline layer. Contact time, adsorbent dose, solution pH, adsorption kinetics, adsorption isotherm and recyclability were studied. The method at the optimum conditions exhibited high performance with high mercury removal percentage of up to 99% with a maximum adsorption capacity 12.5 and 157.1 mg/g for CuFe2O4 and CuFe2O4/PANI, respectively. The adsorption processes were fitted to Langmuir isotherms. The adsorption behavior of CuFe2O4@PANI composite towards Hg2+ ions is attributed to the soft acid–soft base strong interaction between PANI and Hg(II) ions. High stability and enhanced re-usability are offered using CuFe2O4@PANI composite due to its enhanced removal efficiency. No significant removal decrease was noticed after five adsorption–desorption cycles. In addition, it possesses an easy removal from aqueous solutions by external magnetic field after adsorption experiments. These indicated the enhancement of polyaniline to the surface of CuFe2O4 toward the adsorption of mercury from aqueous solutions.

Herein, we present for the first time a novel potentiometric sensor based on the stimulus-responsive molecularly imprinted polymer (MIP) as a selective receptor for neutral dopamine determination. This smart receptor can change its capabilities to recognize according to external environmental stimuli. Therefore, MIP-binding sites can be regenerated in the polymeric membrane by stimulating with stimulus after each measurement. Based on this effect, reversible detection of the analyte via potentiometric transduction can be achieved. MIPs based on 4-vinylphenylboronic acid as the functional monomer were prepared as the selective receptor. This monomer can successfully bind to dopamine via covalent binding and forming a five- or six-membered cyclic ester in a weakly alkaline aqueous solution. In acidic medium, the produced ester dissociates and regenerates new binding sites in the polymeric membrane. The proposed smart sensor exhibited fast response and good sensitivity towards dopamine with a limit of detection 0.15 µM over the linear range 0.2–10 µM. The selectivity pattern of the proposed ISEs was also evaluated and revealed an enhanced selectivity towards dopamine over several phenolic compounds. Constant-current chronopotentiometry is used for evaluating the short-term potential stability of the proposed ISEs. The obtained results confirm that the stimulus-responsive MIPs provide an attractive way towards reversible MIP-based electrochemical sensors designation.

A facile eco-friendly approach for acetampirid pesticide removal is presented. The method is based on the use of micro- and mesoporous activated carbon (TPAC) as a natural adsorbent. TPAC was synthesized via chemical treatment of tangerine peels with phosphoric acid. The prepared activated carbon was characterized before and after the adsorption process using Fourier- transform infrared (FTIR), X-ray diffraction (XRD), particle size and surface area. The effects of various parameters on the adsorption of acetampirid including adsorbent dose (0.02–0.2 g), pH 2–8, initial adsorbate concentration (10–100 mg/L), contact time (10–300 min) and temperature (25–50 °C) were studied. Batch adsorption features were evaluated using Langmuir and Freundlich isotherms. The adsorption process followed the Langmuir isotherm model with a maximum adsorption capacity of 35.7 mg/g and an equilibration time within 240 min. The adsorption kinetics of acetamiprid was fitted to the pseudo-second-order kinetics model. From the thermodynamics perspective, the adsorption was found to be exothermic and spontaneous in nature. TPAC was successfully regenerated and reused for three consecutive cycles. The results of the presented study show that TPAC may be used as an effective eco-friendly, low cost and highly efficient adsorbent for the removal of acetamiprid pesticides from aqueous solutions.

In this research, CuFe2O4 nanoparticles were synthesized by co-precipitation methods and modified by coating with thiophene for removal of Hg(II) ions from aqueous solution. CuFe2O4 nanoparticles, with and without thiophene, were characterized by x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX), high-resolution transmission electron microscopy (HRTEM) and Brunauer−Emmett−Teller (BET). Contact time, adsorbent dose, solution pH, adsorption kinetics, adsorption isotherm and recyclability were studied. The maximum adsorption capacity towards Hg2+ ions was 7.53 and 208.77 mg/g for CuFe2O4 and CuFe2O4@Polythiophene composite, respectively. Modification of CuFe2O4 nanoparticles with thiophene revealed an enhanced adsorption towards Hg2+ removal more than CuFe2O4 nanoparticles. The promising adsorption performance of Hg2+ ions by CuFe2O4@Polythiophene composite generates from soft acid−soft base strong interaction between sulfur group of thiophene and Hg(II) ions. Furthermore, CuFe2O4@Polythiophene composite has both high stability and reusability due to its removal efficiency, has no significant decrease after five adsorption−desorption cycles and can be easily removed from aqueous solution by external magnetic field after adsorption experiments took place. Therefore, CuFe2O4@Polythiophene composite is applicable for removal Hg(II) ions from aqueous solution and may be suitable for removal other heavy metals.

A simple, efficient and reliable analytical method was developed and used for the determination of the fluvoxamine drug (FLV) in pharmaceutical preparations and biological fluids. The method is based on the cost-effective screen-printed platform for the potential transduction of the drug. Host-tailored molecular imprinting polymer (MIP) was integrated with the potentiometric platform as a recognition receptor, in which FLV, acrylamide (AAm), ethylene glycol dimethacrylate (EGDMA) and acetonitrile were used as a template, functional monomer, cross-linker, and solvent, respectively. MIP particles were dispersed in plasticized poly (vinyl chloride) (PVC) and the membrane was drop-casted on carbon screen-printed electrode. The MIP, in addition to non-imprinted polymers (NIP), was characterized and the binding experiment revealed high affinity and adsorption capacity of MIP towards FLV. The proposed sensor displayed near-Nernstian cationic slope of 55.0 ± 0.8 mV/decade (r2 = 0.999) with a low detection limit of 4.8 × 10−6 mol/L over a wide pH range (3.0−8.5). The electrochemical features of the proposed sensors including electrochemical impedance spectroscopy (EIS) and chronopotentiometry measurements (CP) in the presence of multi-walled carbon nanotubes (MWCNTs) as a solid contact transducer were also investigated. The applications of the proposed sensor for the determination of FLV in different dosage forms with recovery values (98.8%−101.9%) and (97.4%−101.1%), respectively compared with the reference HPLC method with acceptedFandt-student tests values at the 95% confidence level.

Herein, we present a new validated potentiometric method for fluoxetine (FLX) drug monitoring. The method is based on the integration of molecular imprinting polymer (MIP) beads as sensory elements with modified screen-printed solid contact ion-selective electrodes (ISEs). A multi-walled carbon nanotube (MWCNT) was used as a nanomaterial for the ion-to-electron transduction process. The prepared MIP beads depend on the use of acrylamide (AAm) and ethylene glycol dimethacrylic acid (EGDMA) as a functional monomer and cross-linker, respectively. The sensor revealed a stable response with a Nernstian slope of 58.9 ± 0.2 mV/decade and a detection limit of 2.1 × 10−6 mol/L in 10 mmol/L acetate buffer of pH 4.5. The presented miniaturized sensors revealed good selectivity towards FLX over many organic and inorganic cations, as well as some additives encountered in the pharmaceutical preparations. Repeatability, reproducibility and stability have been studied to evaluate the analytical features of the presented sensors. These sensors were successfully applied for FLX assessment in different pharmaceutical formulations collected from the Egyptian local market. The obtained results agreed well with the acceptable recovery percentage and were better than those obtained by other previously reported routine methods.

A new SnO2/CeO2 nano-composite catalyst was synthesized, characterized and used for the removal of alizarin dyes from aqueous solutions. The composite material was prepared using a precipitation method. X-ray powder diffractometry (XRD), high resolution transmission electron microscopy (HR-TEM), Brunauer−Emmett−Teller methodology (BET) and Fourier Transform Infrared Spectrometry (ATR-FTIR) were utilized for the characterization of the prepared composite. The prepared nano-composite revealed high affinity for the adsorption and decomposition of alizarin dyes. The adsorption capacity under different experimental conditions (adsorbate concentration, contact time, adsorbent dose and pH) was examined. Under optimized experimental conditions, the removal of alizarin yellow, alizarin red and alizarin-3-methylimino-diacetic acid dyes from aqueous solutions was about 96.4%,87.8% and 97.3%, respectively. The adsorption isotherms agreed with the models of Langmuir, Freundlich and Temkin isotherms.

Potentiometric sensors have a great influence on the determination of most various compounds in their matrices. Therefore, efficient and new sensors were introduced to measure sodium Deoxycholate (NaDC) as a bile acid salt. These sensors are based on NaDC imprinted polymer (MIP) as sensory element. The MIP beads were synthesized using thermal polymerization pathway, in which acrylamide (AAm), ethylene glycol dimethacrylate (EGDMA), NaDC, and benzoyl peroxide (BPO) were used as the functional monomer, cross-linker, template, and initiator, respectively. The proposed sensors were fabricated using a coated screen-printed platform and the sensing membrane was modified by single-walled carbon nanotubes (SWCNTs) as an ion-to-electron transducer. The sensors exhibited high sensitivity that reached 4.7 × 10−5 M of near-Nernestian slope (−60.1 ± 0.9 mV/decade, r2 = 0.999 (n= 5)). In addition, the sensors revealed high selectivity, long lifetime, high potential stability, and conductivity that ensure reproducible and accurate results over a long time. MIP characterization was performed using Fourier Transform-Infrared (FT-IR) and a scanning electron microscope (SEM). Regarding the interaction of NaDC with serum albumin (SA), albumin is determined in human serum samples as human serum albumin (HSA), which was collected from different volunteers of different ages and gender.

Screen-printed membrane sensors based on the use of paper and ceramic substrates are fabricated, characterized, and used for rapid batch and continuous monitoring of CrIII in the form of CrO42− in some industrial products and wastewater samples. Strips of paper and ceramic platforms (15 × 5 mm) were covered with conductive carbon paint and then modified with polyaniline (PANI) film, to act as an ion-to-electron transducer, followed by a drop casting of plasticized poly (vinyl chloride) (PVC) Rhodamine-B chromate membrane as a recognition sensing material. In a 5.0 mmol L−1 Trizma buffer solution of pH ~8, the fabricated paper and ceramic based membrane sensors exhibited a near Nernstian response for CrVI ion with slopes of −29.7 ± 0.5 and −28.6 ± 0.3 mV decade−1, limit of detection 2.5 × 10−5 and 2.4 × 10−6 mol L−1 (1.3−0.12 µg mL−1), and linear concentration range 7.5 × 10−3−5.0 × 10−5 and 7.5 × 10−3−1.0 × 10−5 mol L−1 (390-0.5 µg mL−1), respectively. Both sensors exhibited fast and stable potentiometric response, excellent reproducibility, and good selectivity with respect to a number of common foreign inorganic species. Impedance spectroscopy and chronopotentiometry data revealed a small resistance and a larger double layer capacitance due to the presence of the intermediate polyaniline (PAN) conductive layer. Furthermore, the formation of a water layer between the ion selective membrane (ISM) and the underlying conductor polymer and between the conducting polymer and the carbon conducting surface was greatly reduced. The developed disposable solid-contact potentiometric sensors offer the advantages of simple design, long term potential stability, flexibility, miniaturization ability, short conditioning time, and cost effectiveness that enable mass production. The sensors were successfully used for static and hydrodynamic measurements of total chromium in some leather tanning wastewater and nickel-chrome alloy samples. The results compare favorably with data obtained by atomic absorption spectrometry.

The cloud point extraction (CPE) method was successfully used for the isolation and pre-concentration of ultra-low concentration of Pb prior to its determination by flame atomic absorption spectrometry (FAAS). Lead(II) reacts with methyl 4,20-diisobutyl-2,5,8,16,19,22- hexaoxo-7,17-dipropyl-3,6,9,15,18,21-hexaaza-1(2,6)-pyridinacyclo-docosaphane-10-carboxylate (DLNL) as chelating agent in the presence of octylphenoxypolyethoxyethanol (Triton X-114) as a nonionic surfactant giving a surfactant-rich phase chelate which could be used for CPE. Factors affecting the CPE such as solution pH, concentrations of the chelating ligand and surfactant, temperature of equilibration, and time were optimized. The efficacy features of the proposed protocol such as linear range, lower limit of detection, pre-concentration, and progress factors were evaluated. The method revealed a wide linear range in the range of 7−250 ng/mL of Pb2+ with a limit of detection of 5 ng/mL using FAAS. Validation of the presented protocol revealed good performance characteristics including high between-batch repeatability, high precision, wide linear range, low limit of detection, and acceptable accuracy. The presented procedure was successfully introduced for the separation and quantification of lead (II) in wastewater samples with acceptable results.

Novel potentiometric solid-contact ion-selective electrodes (SC/ISEs) based on molecularly imprinted polymers (MIPs) as sensory carriers (MIP/PANI/ISE) were prepared and characterized as potentiometric sensors for flucarbazone herbicide anion. However, aliquat S 336 was also studied as a charged carrier in the fabrication of Aliquat/PANI/ISEs for flucarbazone monitoring. The polyaniline (PANI) film was inserted between the ion-sensing membrane (ISM) and the electronic conductor glassy carbon substrate (GC). The sensors showed a noticeable response towards flucarbazone anions with slopes of −45.5 ± 1.3 (r2 = 0.9998) and −56.3 ± 1.5 (r2 = 0.9977) mV/decade over the range of 10−2−10−5, 10−2−10−4 M and detection limits of 5.8 × 10−6 and 8.5 × 10−6 M for MIP/PANI/ISE and Aliguat/PANI/ISE, respectively. The selectivity and long-term potential stability of all presented ISEs were investigated. The short-term potential and electrode capacitances were studied and evaluated using chronopotentiometry and electrochemical impedance spectrometry (EIS). The proposed ISEs were introduced for the direct measurement of flucarbazone herbicide in different soil samples sprayed with flucarbazone herbicide. The results agree well with the results obtained using the standard liquid chromatographic method (HPLC).

A new simple potentiometric sensor is developed and presented for sensitive and selective monitoring of dimethylamine (DMA). The sensor incorporates a molecularly imprinted polymer, with a pre-defined specific cavity suitable to accommodate DMA. The molecularly imprinted polymer (MIP) particles were dispersed in an aplasticized poly(vinyl chloride) matrix. The MIP is synthesized by using a template molecule (DMA), a functional monomer (acrylamide, AM), cross-linker (ethylene glycol dimethacrylate, EGDMA) and initiating reagent (benzoylperoxide, BPO). Using Trizma buffer solution (5 mmol L−1, pH 7.1), the sensor exhibits a rapid, stable and linear response for 1.0 × 10−5 to 1.0 × 10−2 mol L−1 DMA+ with a calibration slope of 51.3 ± 0.3 mV decade−1, and a detection limit of 4.6 × 10−6 mol L−1 (0.37 µg mL−1). The electrode exhibited a short response time (10 s) and stable potential readings (± 0.5 mV) for more than 2 months. Potentiometric selectivity measurements of the sensor reveal negligible interferences from most common aliphatic and aromatic amines. High concentration levels (100-fold excess) of many inorganic cations do not interfere. The sensor is successfully used for quantification of low levels of DMA down to 0.5 µg mL−1. Verification of the presented method was carried out after measuring the detection limit, working linearity range, ruggedness of the method, accuracy, precision, repeatability and reproducibility. Under flow-through conditions, the proposed sensor in its tubular form is prepared and introduced in a two-channel flow injection setup for hydrodynamic determination of DMA. The sampling rate is 50−55 samples h−1. The sensor is used to determine DMA in different soil samples with an accuracy range of 97.0−102.8%.

Novel biomimetic potentiometric ion-selective electrodes (ISEs) were fabricated and designed for the assessment of aminoacridine (ACR) based on newly synthesized imprinted polymer (MIP) membranes. Thermal polymerization of methacrylic acid (MAA) or acrylamide (AM) as function monomer, aminoacridine as a template and ethylene glycol dimethacrylate (EGDMA) as across-linker, were utilizedto give the molecular recognition part. The membranes of sensors I andII consist of MIP based MAA and AM, respectively, dispersed in a poly(vinyl chloride) membrane plasticized with dioctyl phthalate (DOP) in the ratio of 3.0 wt%, 32.2 wt% and 64.8 wt%, respectively. Sensors III and IV were similarly prepared with added 1.0 wt% tetraphenyl borate (TPB−) as an anionic discriminator. Sensors I and II exhibited near-Nernstian potential response to ACR+ with slopes of 51.2 ± 1.3 and 50.5 ± 1.4 mV/decade in a 0.01 M phosphate buffer of pH 6.0. The linear response coversthe concentration range of 5.2 × 10−6 to 1.0 × 10−3 M with a detection limit of 0.05 and 0.17 μg/mL for sensors I and II, respectively. The performance characteristics of these sensors were evaluated under static and hydrodynamic mode of operations. They were used for quality control assessment of aminoacridine in some pharmaceutical preparations and biological samples.

A novel single-piece all-solid-state ion-selective electrode (SC/ISE) based on carbon-screen printed is introduced. Polyaniline (PANI) is dissolved in a membrane cocktail that contains the same components used for making a conventional ion-selective polyvinyl chloride (PVC) matrix membrane. The membrane, having the PANI, is directly drop-casted on a carbon substrate (screen-printed-carbon electrode). PANI was added to act as an intermediary between the substrate and the membrane for the charge transfer process. Under non-equilibrium sensing mechanism, the sensors revealed high sensitivity towards 2,4-dichlorophenol (DCP) over the linearity range 0.47 to 13 µM and a detection limit 0.13 µm. The selectivity was measured by the modified separate solution method (MSSM) and showed good selectivity towards 2,4-DCP over the most commonly studied ions. All measurements were done in 30 mm Tris buffer solution at a pH 5.0. Using constant-current chronopotentiometry, the potential drift for the proposed electrodes was checked. Improvement in the potential stability of the SPE was observed after the addition of PANI in the sensing membrane as compared to the corresponding coated-wire electrode (membrane without PANI). The applicability of the sensor has been checked by measuring 2,4-DCP in different water samples and the results were compared with the standard HPLC method.

Screen-printed ion-selective electrodes were designed and characterized for the assessment of cyromazine (CYR) pesticide. A novel approach is to design tailor-made specific recognition sites in polymeric membranes using molecularly imprinted polymers for cyromazine (CR) determination (sensor I). Another sensor (sensor II) is the plasticized PVC membrane incorporating cyromazine/tetraphenyl borate ion association complex. The charge-transfer resistance and water layer reached its minimal by incorporating Polyaniline (PANI) solid-contact ISE. The designed electrodes demonstrated Nernstain response over a linear range 1.0 × 10−2−5.2 × 10−6 and 1.0 × 10−2−5.7 × 10−5 M with a detection limit 2.2 × 10−6 and 8.1 × 10−6 M for sensors I and II, respectively. The obtained slopes were 28.1 ± 2.1 (r2 = 0.9999) and 36.4 ± 1.6 (r2 = 0.9991) mV/decade, respectively. The results showed that the proposed electrodes have a fast and stable response, good reproducibility, and applicability for direct measurement of CYR content in commercial pesticide preparations and soil samples sprayed with CYR pesticide. The results obtained from the proposed method are fairly in accordance with those using the standard official method.

Possible improvement of the performance characteristics, reliability and selectivity of solid-contact nitrate ion-selective electrodes (ISE) (SC/NO3−-ISE) is attained by the application of a nitron-nitrate (Nit+/NO3−) ion association complex and inserting multi-walled carbon nanotubes (MWCNTs) as an ion-to-electron transducer between the ion sensing membrane (ISM) and the electronic conductor glassy carbon (GC) substrate. The potentiometric performance of the proposed electrode revealed a Nernstian slope −55.1 ± 2.1 (r² = 0.997) mV/decade in the range from 8.0 × 10−8−1 × 10−2 M with a detection limit of 2.8 × 10−8 (1.7 ng/mL). Selectivity, repeatability and reproducibility of the proposed sensors were considerably improved as compared to the coated disc electrode (GC/NO3−-ISE) without insertion of a MWCNT layer. Short-term potential stability and capacitance of the proposed sensors were tested using a current-reversal chronopotentiometric technique. The potential drift in presence of a MWCNT layer decreased from 167 μVs−1 (i.e., in absence of MWCNTs) to 16.6 μVs−1. In addition, the capacitance was enhanced from 5.99 μF (in absence of MWCNTs) to 60.3 μF (in the presence of MWCNTs). The presented electrodes were successfully applied for nitrate determination in real samples with good accuracy.

Solid-contact potentiometric ion-selective electrodes (SC-ISEs) for thallium determination have been designed using multiwall carbon nanotubes (MWCNTs) as the ion-to-electron transducer. Dispersed MWCNTs were drop-casted over a gold plate electrode. Two different crown ethers were used in the sensing membrane for the recognition of thallium (I). Sensorsbased on dibenzo-18-crown-6 (DB18C6) as a neutral carrier and NaTPB as an anionic additive exhibited a near Nernstian response of 57.3 mV/decade towards Tl+ ions over the activity range 4.5 × 10−6–7.0 × 10−4 M, with a limit of detection of 3.2 × 10−7 M. The time required to achieve 95% of the steadyequilibrium potential was βML) between dibenzo-18-crown-6 and thallium (I) (i.e., 5.99) was measured using the sandwich membrane technique. The potential response was pH independent over the range 3.0–9.5. The introduction of MWCNTs as an electron-ion-transducer layer between gold plate and the sensing membrane lead to a smaller membrane resistance and a large double layer capacitance, which was proven using impedance spectra and chronopotentiometry (i.e., 114.9 ± 12 kΩ, 52.1 ± 3.3 pF, 200 ± 13.2 kΩ, and 50 ± 4.2 µF). Additionally, reduction ofthe water layer between the sensing membrane and the underlying conductor wastested. Thus, it is clear that MWCNTs can be used as a transducing layer in SC-ISEs. The proposed sensor was introduced as an indicator electrode for potentiometric titration of single and ternary mixtures of I−, Br−, and S2− anions.

Molecularly imprinted polymer (MIP) receptors have been synthesized, characterized, and applied as new selective receptors in solid-contact ion selective electrodes (ISEs) towards non-dissociated 3,5-dihydroxytoluene (orcinol). Two monomers, namely methacrylic acid (MAA) and acrylamide (AA), were used in the preparation of MIP receptors. Graphene (Gr) was used as the solid contact material between the sensing membrane and the electrical contact substrate. Based on non-equilibrium sensing mechanism, the proposed sensors reveal observably enhanced detection sensitivity towards orcinol with detection limits 1.7 × 10−5 and 3.3 × 10−6 M for sensors based on MIP/MAA and MIP/AA, respectively. The selectivity coefficients measured by the modified separate solution method (MSSM) for the proposed sensors showed good selectivity towards orcinol over most common other phenols and inorganic anions. All measurements were made in the presence of 30 mM phosphate buffer solution (PBS) with a pH of 7.0. Potential stability for the proposed sensors was tested by constant-current chronopotentiometry. No water films were formed between the sensing membrane and the electron conductor substrate. The applicability of MIP/MAA incorporated ISE has been checked by recovery test of orcinol in the presence of soil matrix and by standard addition method.

Herein, we present reliable, robust, stable, and cost-effective solid-contact ion-selective electrodes (ISEs) for perchlorate determination. Single-walled carbon nanotubes (SWCNTs) were used as solid-contact material and indium (III) 5, 10, 15, 20-(tetraphenyl) porphyrin chloride (InIII-porph) as an ion carrier. The sensor exhibited an improved sensitivity towards ClO4− ions with anionic slope of −56.0 ± 1.1 (R2 = 0.9998) mV/decade over a linear range 1.07 × 10−6 − 1.0 × 10−2 M and detection limit of 1.8 × 10−7 M. The short-term potential stability and the double-layer capacitance were measured by chronopotentiometric and electrochemical impedance spectroscopy (EIS) measurements, respectively. The sensor is used for ClO4− determination in fireworks and propellant powders. The results fairly agree with data obtained by ion chromatography.

In this work, we demonstrated proof-of-concept for the use of ion-selective electrodes (ISEs) as a promising tool for the assessment of total antioxidant capacity (TAC). Novel membrane sensors for 2,6-dichlorophenolindophenolate (DCPIP) ions were prepared and characterized. The sensors membranes were based on the use of either CuII-neocuproin/2,6-dichlorophenolindo-phenolate ([Cu(Neocup)2][DCPIP]2) (sensor I), or methylene blue/2,6-dichlorophenolindophenolate (MB/DCPIP) (sensor II) ion association complexes in a plasticized PVC matrix. The sensors revealed significantly enhanced response towards DCPIP ions over the concentration range 5.13 × 10−5−1.0 × 10−2 and 5.15 × 10−5−1.0 × 10−2 M at pH 7 with detection limits of 6.3 and 9.2 µg/mL with near-Nernstian slope of −56.2 ± 1.7 and −51.6 ± 2 mV/decade for sensors I and II, respectively. The effects of plasticizers and various foreign common ions were also tested. The sensors showed enhanced selectivity towards DCPIP over many other phenolic and inorganic ions. Long life span, high potential stability, high reproducibility, and fast response were also observed. Method validation was also verified by measuring the detection limit, linearity range, accuracy, precision, repeatability and between-day-variability. The sensors were introduced for direct determination of TAC in fresh and canned juice samples collected from local markets. The obtained results agreed fairly well with the data obtained by the standard method.

New reliable and robust potentiometric ion-selective electrodes were fabricated using poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) as the solid contact between the sensing membrane and electrical substrate for an acetylcholine (ACh) bioassay. A film of PEDOT/PSS was deposited on a solid carbon screen-printed platform made from ceramic substrate. The selective materials used in the ion-selective electrode (ISE) sensor membrane were acetylcholinium tetraphenylborate (ACh/TPB/PEDOT/PSS-ISE) (sensor I) and triacetyl-β-cyclodextrin (β-CD/PEDOT/PSS-ISE) (sensor II). The sensors revealed clear enhanced Nernstian response with a cationic slope 56.4 ± 0.6 and 55.3 ± 1.1 mV/decade toward (ACh+) ions over the dynamic linear range 1.0 × 10−6–1 × 10−3 and 2.0 × 10−6–1.0 × 10−3 M at pH 5 with limits of detection 2.0 × 10−7 and 3.2 × 10−7 M for sensors I and II, respectively. The selectivity behavior of both sensors was also tested and the sensors showed a significant high selectivity toward ACh+ over different common organic and inorganic cations. The stability of the potential response for the solid-contact (SC)/ISEs was evaluated using a chronopotentiometric method and compared with that of electrodes prepared without adding the solid-contact material (PEDOT/PSS). Enhanced accuracy, excellent repeatability, good reproducibility, potential stability, and high selectivity and sensitivity were introduced by these cost-effective sensors. The sensors were also used to measure the activity of acetylcholinesterase (AChE). A linear plot between the initial rate of the hydrolysis of ACh+ substrate and enzyme activity held 5.0 × 10−3–5.2 IU L−1 of AChE enzyme. Application to acetylcholine determination in human serum was done and the results were compared with the standard colorimetric method.

Two novel all-solid-state potentiometric sensors for the determination of azide ion are prepared and described here for the first time. The sensors are based on the use of iron II-phthalocyanine (Fe-PC) neutral carrier complex and nitron-azide ion-pair complex (Nit-N3−) as active recognition selective receptors, tetradodecylammonium tetrakis(4-chlorophenyl) borate (ETH 500) as lipophilic cationic additives and poly(octylthiophene) (POT) as the solid contact material on carbon screen-printed devices made from a ceramic substrate. The solid-contact material (POT) is placed on a carbon substrate (2 mm diameter) by drop-casting, followed, after drying, by coating with a plasticized PVC membrane containing the recognition sensing complexes. Over the pH range 6-9, the sensors display fast (< 10 s), linear potentiometric response for 1.0 × 10−2–1.0 × 10−7 M azide with low detection limit of 1.0 × 10−7 and 7.7 × 10−8 M (i.e., 6.2–4.8 ng/ml) for Fe-PC/POT/and Nit-N3−/POT based sensors, respectively. The high potential stability and sensitivity of the proposed sensors are confirmed by electrochemical impedance spectroscopy (EIS) and constant-current chronopotentiometry measurement techniques. Strong membrane adhesion and absence of delamination of the membrane, due to possible formation of a water film between the recognition membranes and the electron conductor are also verified. The proposed sensors are successfully applied for azide quantification in synthetic primer mixture samples. Advantages offered by these sensors are the robustness, ease of fabrication, simple operation, stable potential response, high selectivity, good sensitivity and low cost.

Herein, a facile route leading to good single-walled carbon nanotubes (SWCNT) dispersion or poly (3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) based single-piece nanocomposite membrane is proposed for trace determination of Cu2+ ions. The single-piece solid contact Cu2+-selective electrodes were prepared after drop casting the membrane mixture on the glassy-carbon substrates. The prepared potentiometric sensors revealed a Nernstian response slope of 27.8 ± 0.3 and 28.1 ± 0.4 mV/decade over the linearity range 1.0 × 10−3 to 2.0 × 10−9 and 1.0 × 10−3 to 1.0 × 10−9 M with detection limits of 5.4 × 10−10 and 5.0 × 10−10 M for sensors based on SWCNTs and PEDOT/PSS, respectively. Excellent long-term potential stability and high hydrophobicity of the nanocomposite membrane are recorded for the prepared sensors due to the inherent high capacitance of SWCNT used as a solid contact material. The sensors exhibited high selectivity for Cu2+ ions at pH 4.5 over other common ions. The sensors were applied for Cu2+ assessment in tap water and different tea samples. The proposed sensors were robust, reliable and considered as appealing sensors for copper (II) detection in different complex matrices.

All-solid-state potentiometric sensors were prepared by using polyaniline (PANI) as the solid contact material. A film of PANI (thickness approximately being 0.25 µm) was deposited on a solid substrate (carbon screen printed platform). The PANI layer was subsequently coated with an ion-selective membrane (ISM) containing uniform-sized molecularly imprinted nanoparticles to produce a solid-contact ion-selective electrode (SC/ISE) for bispyribac herbicide (sensor I). In addition, aliquat 336 was also used as an ion exchanger in plasticized PVC membrane (sensor II). The proposed sensors revealed a remarkably improved sensitivity towards bispyribac ions with anionic slopes of −47.8 ± 1.1 (r2 = 0.9995) and −44.4 ± 1.4 (r2 = 0.9997) mV/decade over a linear range 1.0 × 10−2⁻8.6 × 10−6 M, 1.0 × 10−2⁻9.0 × 10−6 M and detection limits of 1.33 and 1.81 µg/mL for sensors I and II, respectively.Selectivity of both sensors is significantly high for different common pesticides and inorganic anions. The potential stability of the SC/ISEs was studied using chronopotentiometry. Electrochemical impedance spectrometry was used to understand the charge-transfer mechanisms of the different types of ion-selective electrodes studied. The impedance response of the electrodes was modelled by using equivalent electrical circuits. The sensors were used for a direct measurement of the bispyribac content in commercial herbicide formulations and soil samples collected from agricultural lands planted with rice and sprayed with bispyribac herbicide. The results agree fairly well with data obtained using HPLC method.

Iron(II)-(1,10-phenanthroline) complex imprinted membrane was prepared by ionic imprinting technology. In the first step, Fe(II) established a coordination linkage with 1,10-phenanthroline and functional monomer 2-vinylpyridine (2-VP). Next, the complex was copolymerized with ethylene glycol dimethacrylate (EGDMA) as a crosslinker in the presence of benzoyl peroxide (BPO) as an initiator. Potentiometric chemical sensors were designed by dispersing the iron(II)-imprinted polymer particles in 2-nitrophenyloctyl ether (o-NPOE) plasticizer and then embedded in poly vinyl chloride (PVC) matrix. The sensors showed a Nernstian response for [Fe(phen)3]2+ with limit of detection 3.15 ng mL−1 and a Nernstian slope of 35.7 mV per decade.