Sensitive Potentiometric Sensor Research Articles

Highly Sensitive Potentiometric pH Sensor Based on Polyaniline Modified Carbon Fiber Cloth for Food and Pharmaceutical Applications.

This study introduces a potentiometric pH sensor that is extremely sensitive and specifically designed for food and pharmaceutical applications. The sensor utilizes a pH-sensitive interface fabricated by electropolymerizing polyaniline (PANI) on carbon fiber cloth (CFC). Structural and morphological analyses of PANI-CFC and CFC have been conducted by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The investigation of the functional groups was conducted by using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The electrochemical characteristics were assessed by utilization of cyclic voltammetry (CV) and open-circuit potential (OCP) measurements in a three-electrode configuration. The sensor exhibited a sensitivity of 60.9 mV/pH, while retaining consistent performance within the pH range of 4 to 12. The repeatability and robustness of the sensors were verified. The accuracy of the PANI-CFC sensor was confirmed by validation using real samples, demonstrating its compatibility with commercially available pH sensors. The application of density functional theory (DFT) calculations revealed an interaction energy of -173.2886 kcal/mol, indicating a strong affinity of H+ ions towards PANI-CFC electrode. Further investigation was conducted to examine the chemical reactivity of PANI, revealing a HOMO-LUMO energy gap of -0.98 eV. This study highlights the PANI-CFC sensor as a reliable and efficient pH-sensing platform for food and pharmaceuticals applications, performing robustly in both laboratory and real-world settings.

High-Performance Electrochemical Creatinine Sensors Based on β-Lead Dioxide/Single-Walled Carbon Nanotube Electrodes.

Creatinine is an important biomarker of kidney function and muscular metabolism. In this paper, we developed the β-lead dioxide/single-walled carbon nanotube (β-PbO2/CNT) and the β-PbO2/CNT ion-selective electrode (β-PbO2/CNT/ISE), which were used as highly sensitive potentiometric sensors for creatinine detection. The fabricated electrodes exhibited highly pH-sensitive characteristics due to the synergistic effect of the electrochemical properties of CNT and β-PbO2. Moreover, an ammonium-ion-selective membrane coating allowed the β-PbO2/CNT electrode to be NH4+-selective for direct detection of the ammonium ion. By exploiting the electrochemical characteristics of these electrodes, the creatinine assay was established through the one-step selective conversion of creatinine by creatinine deiminase, in which the OH- and NH4+ generated by the enzymatic reaction were detected using β-PbO2/CNT and β-PbO2/CNT/ISE electrodes as pH- and NH4+-responsive sensors, respectively. The total creatinine assay can be completed within ∼5 min. The assay results from β-PbO2/CNT and β-PbO2/CNT/ISE showed excellent sensitivity values of -75.56 and 64.62 mV in the detection range of 10-400 μM with a fast response (20 s), and the limits of detection were calculated to be 0.06 and 0.13 μM, respectively. Moreover, the developed creatinine sensor showed high selectivity against 11 interfering bio/chemical species with negligible interferences (selectivity coefficient <10-4) and excellent repeatability (>97% within 25 cycles) and long-term stability for 4 weeks of storage. In addition, the feasibility and practicality of the device were successfully demonstrated in human serum tests, with recoveries of 95-104% for PbO2/CNT and 92-110% for PbO2/CNT/ISE.

Construction of novel potentiometric sensors modified with biogenically synthesized metal oxide nanoparticles for sensitive detection of the opioid agonist-antagonist nalbuphine hydrochloride in its injection

Novel and sensitive potentiometric sensors were described for the assay of nalbuphine HCl (NBP) in authentic powder and injection samples. The developed sensors were modified with alumina nanoparticles (Al2O3NPs) and copper oxide nanoparticles (CuONPs). The nanoscale materials were synthesized using the extract of Salvia officinalis leaves in an environmentally friendly manner. The synthesized metal oxides were fully confirmed by various analytical techniques. Scanning electron microscope confirmed the morphology of nanosized materials with even distribution and particle size of 55.07 ± 4.15 and 59.48 ± 4.50 nm for Al2O3NPs and CuONPs, respectively. The modified sensors were prepared in three different steps. Nalbuphine hydrochloride was mixed with phosphomolybdic acid to prepare the sensor material nalbuphine phosphomolybdate (NBP-PM). It was then mixed with polyvinyl chloride in the presence of o-nitrophenyl ether and metal oxide nanoparticles to form the membrane matrix. Finally, a copper wire was coated with the sensing material. Excellent potentials of 1.0 × 10−8-1.0 × 10−2 and 1.0 × 10−9-1.0 × 10−2 mol L−1 were measured with lower assay limits of 4.8 × 10−9 and 5.0 × 10−10 mol L−1. The average detection % were 99.28 ± 0.58% and 99.52 ± 0.28% for NBP-PM-Al2O3NPs and NBP-PM-CuONPs, correspondingly. The suitability of the described sensors was investigated in terms of various validation criteria, and the modified sensors exposed excellent applicability and insurance for the quantification of nalbuphine hydrochloride in its bulk samples and injections compared with another standard sensor. It is obvious that the developed NBP-PM-Al2O3NPs and NBP-PM-CuONPs will serve as suitable sensors for the determination of NBP.

Selective Ion‐pair Potentiometric Sensor for the Determination of Ondansetron Hydrochloride in Different Matrixes

A facile, novel, and, sensitive potentiometric sensor has been developed to quantitatively determine ondansetron hydrochloride in bulk and pharmaceutical dosage forms. The sensor comprised an ion-pair between ondansetron hydrochloride and ammonium reineckate reagent, as an electrochemically active substance, on a polyvinyl chloride (PVC) matrix. Synthesis optimization was carried out by firstly altering the proportion of the ion-pair, PVC, and the plasticizer and subsequently, many plasticizer types have been investigated to realize the best performance. The optimum electrode consisted of 48.5 % polyvinyl chloride, 48.5 % dibutyl phthalate, and 3 % ionic pair complex and has shown a respectful Nernstian relationship within a linear range of (5.06×10−6–2592.92×10−6 M) and a slope of 57.277 mV×decade−1 in response to the drug. The electrode worked perfectly in a pH range of (1.9–6.1) where the analyte kept dissolved. Interestingly, the electrode demonstrated a fast response time of 30 sec, a lower limit of detection of 4.83×10−6 M, and an electrode lifetime of up to 30 days. The prepared electrode was applied successfully to determine the drug in its pharmaceutical dosage forms and the method validity was established. Hence, the electrode might be applied easily for the routine analysis of ondansetron hydrochloride in both scientific labs and drug industry.

Preparation of nanopillar array electrode of iridium oxide for high performance of pH sensor and its real‐time sweat monitoring

AbstractA highly sensitive potentiometric pH sensor was developed based on nanopillar array electrodes of iridium oxide. The as‐prepared pH sensor exhibited a high pH sensitivity (69.43 mV/pH), fast response time (8.1 s), and good durability (0.76 mV/h). The sensing performance of the pH sensor was maintained under mechanical bending and even after 1000 repetitive bending/releasing cycles. As a proof‐of‐concept, a wearable headband sensor was fabricated by integrating the pH sensor with a wireless electronic module based on a printed circuit board. The on‐body test indicated that the wearable pH sensor provides reliable and stable data in the real‐time monitoring of pH changes in human sweat during stationary indoor cycling. The pH sensors based on nanopillar array electrodes of iridium oxide have great potential in many portable or wearable applications in healthcare systems, non‐invasive diagnostics, environmental analysis, and food sensors.

A portable solid-contact potentiometric sensor based on zeolite-carbon paste for assay of prucalopride succinate in tablet dosage form: Green profile assessment

A new, simple, highly sensitive potentiometric sensor was fabricated for the determination of Prucalopride succinate (Pru). The electrochemical sensor was based on the deposition of the ion exchanger (Prucalopride succinate-phosphotungstic acid (Pru-PTA) into the carbon paste which also was fabricated with zeolite particles and dibutyl phthalate to enhance its performance. The proposed sensor exhibits a Nernstian slope of 58.6589 ± 0.47 mV/decade over the linearity range 2 × 10-6 − 1 × 10-2 M Pru (0.1–4.5 × 102 µg/mL) and detection limit 1 × 10-6 M Pru with reasonable selectivity and thermal stability. The method was used for the determination of the studied drug in its pure form with an acceptable % recovery of 100.02 ± 1.3; it was successfully used for the determination of Pru in tablets. The proposed method was proven to be eco-friendly as assessed by two matrices; Analytical Eco-Scale and the recently developed Complementary green analytical procedure index (Complex-GAPI)

Green electrochemical and chromatographic quantifications of the extremolyte ectoine in halophilic bacterial cultures and related pharmaceutical preparations

The realistic implementation of electrochemistry into bacterial biosynthesis monitoring programs has always been a challenging task. In this study, two simple, rapid, selective, and sensitive potentiometric sensors were developed and optimized for quantitative analysis of the extremolyte / osmoprotector ectoine (ECT) in halophilic bacterial cultures and also in its related pharmaceutical products. The developed sensors were a Polyvinyl chloride membrane sensor (ECT-PVC) and a coated graphite sensor (ECT-CG). They were established based on the ion association complex of ectoine cation with phosphotungstic acid (ECT-PTA) counter anion as ion exchange site using dioctyl-phthalate (DOP) as a solvent mediator or plasticizer. The sensors exhibited fast, stable, selective, and linear Nernstian responses over a broad range of concentrations ranging from 1 × 10−5 to 1 × 10−2 M of the studied drug. The developed sensors were optimized and cross-validated with a proposed HPLC method according to ICH guidelines. The proposed methods were successfully employed to quantify the studied drug in three different types of halophilic bacterial cultures and in an ectoine nasal spray pharmaceutical product. The selected bacteria species were Chromohalobacter salexigens, Halobacillus halophilus, and Halomonas elongata. The proposed methods were statistically compared with the reported methods, demonstrating no significant difference with respect to accuracy and precision. Greenness and environmental impact were also evaluated for the proposed procedures, verifying that they were excellent green and eco-friendly analytical methods.

The novel anionic surfactant selective sensors based on newly synthesized quaternary ammonium salts as ionophores

A series of nitrogen heterocycles containing long alkyl and polyalkyl chains were prepared in the form of quaternary ammonium salts using the one-step procedure in good to excellent yields. The method generally gives rise to exclusive N-alkylation. The newly synthesized quaternary alkylammonium compounds (QAC) characterized by standard analytical methods including IR, 1H- and 13C-NMR, MS and elemental analysis, were theoretically studied and tested as ionophores for surfactant selective sensors. A selective and highly sensitive potentiometric sensors for anionic surfactants (ASs) determination were prepared by using a new QAC-tetraphenylborate (TPB) ion pairs as sensing elements. For each QAC-TPB sensor the response time, selectivity and influence of pH were determined. The electrode with the best response characteristics showed Nernstian response towards dodecyl sulfate (DDS) in the concentration range from 1.5 ∙ 10−7 to 5.0 ∙ 10−3 M and limit of detection of 7.5 ∙ 10−8 M. Also, they were successfully used for ASs determination in pure and real systems.

Optimization of polydopamine imprinted polymer for label free sensitive potentiometric determination of proteins: Application to recombinant human erythropoietin sensing in different matrices

The integration of molecular imprinted polymers (MIPs) with ion selective electrodes (ISE) has been an ideal platform for sensing of biological products. In this work, a facile MIP was constructed over the surface of PVC polymeric membrane using self-assembled dopamine (DA) as a monomer around recombinant human Erythropoietin (rhEPO) as a template. A label free passive ion flux MIP potentiometric sensor was fabricated using tetra butyl ammonium bromide as a marker ion. MIP preparation was optimized for critical factors (monomer concentration and polymerization time) that affect the thickness of the imprinted layer by central composite response surface design. The optimum condition for DA-MIP preparation was found to be 3.79 mg mL−1 DA for 18.14 h with desirability of 0.9919. A highly selective and sensitive potentiometric sensor was obtained by combining membrane surface minimization with superficial imprinting process strategy. The sensor has elicited selectivity for template molecule as confirmed by imprinting factor exceeding 11-fold the values obtained from closely related rhEPO analogues. The imprinted layer surface was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The quantitative determination of rhEPO was established over the range of 1.00–100.00 ng mL−1 (10-9 to 10-11 M) with a limit of detection of 0.33 ng mL−1. The sensor could classify rhEPO-α products in a similar attitude of natural antibodies. The potentiometric sensor was able to quantitate rhEPO in human serum with a limit of detection of 0.50 ng mL−1 and the bioanalytical assay was successfully validated. The proposed MIP biosensor elicited specificity for template recognition and selectivity in biological fluids without the need of immunoaffinity purification. Such approach shall plan the direction towards a portable sensor for doping disclosure in sports cheating.

A new generation of highly sensitive potentiometric sensors based on ion imprinted polymeric nanoparticles/multiwall carbon nanotubes/polyaniline/graphite electrode for sub-nanomolar detection of lead(II) ions

Abstract This paper reports the fabrication of new lead ion potentiometric sensors using 2,2′:6′,6″-terpyridine (Terpy)-based Pb2+-imprinted polymeric (IIP) nanoparticles as the sensing component. Pb2+ ions form a stable 1:2 (metal to ligand) complex with Terpy in acetonitrile solution. The resulting Pb(Terpy)22+ complex was then polymerized with ethyleneglycol dimethacrylate, as a cross-linking monomer, via the precipitation copolymerization method. The imprinting resulted in the enhanced affinity of the material to Pb2+ over alternative competing ions. Thus, the selectivity investigations showed no measurable interference of a variety of transition and heavy metal ions for determination of Pb2+ ions. The sorption/desorption of Pb2+ ions on the IIP nanobeads was quick enough to attain relatively fast response potentiometric sensors with response times of 15–45 s. The synthesized Pb2+-IIP was applied as a sensing unit for the procurement of sensitive potentiometric sensors with high selectivity for sub-nanomolar determination of lead(II), with a limit of detection and a linear range of 3.4 × 10−10 and 5.3 × 10−10-1.0 × 10−1 M, respectively. The optimized pH interval for the maximum sensitivity of the designed sensors was 4.5–8.0. The accuracy of the sensors was explored by the analysis of diverse water samples. The prepared sensors were successfully applied to detect traces of Pb2+ ions in different real aqueous matrices.

A new selective carbon paste electrode for potentiometric analysis of olanzapine

A novel and very sensitive potentiometric sensor with excellent electrochemical properties containing olanzapine- tungstophosphate ion pair as modifier was fabricated for the analysis of olanzapine in real samples. The modified electrode showed Nernstian slope of 59.2 mV decade−1 for olanzapine concentration from 7.5 × 10−7 to 5.6 × 10−4 M and a limit of detection 5.0 × 10−7 M, showing high selectivity. Temperature dependence of the electrode potential response was examined in the temperature range of 15–55 °C, revealing a good thermal stability. Also, it showed a short and at least 2 months stable response of 4 s. The modified electrode was used to the study of the interaction between olanzapine drug and β-cyclodextrin and the relevant binding constant was determined. The electrode was used in the potentiometric titration of different olanzapine concentrations with phosphotungstic acid and also determination of olanzapine in real samples such as olanzapine tablet and human blood serum.

Manganese oxide nanoparticles electrodeposited on graphenized pencil lead electrode as a sensitive miniaturized pH sensor

pH monitoring in micro volume samples is required for environmental and clinical analysis. Low cost, miniaturized and stable metal oxide based pH sensors could be a suitable alternative to glass electrodes. In this study, a sensitive potentiometric solid state pH sensor based on manganese oxide nanoparticles electrodeposited on graphenized pencil lead electrode (MnO2/GPLE) was reported. The prepared MnO2/GPLE was carefully characterized by SEM, XRD and electrochemical techniques. To miniaturize the prepared pH sensor, a stainless steel 304 needle was used as a reference electrode. Selectivity, response time, stability and reproducibility of the miniaturized pH sensor were studied and compared with conventional glass pH electrode. According to experimental results, a near-Nernstian slope of − 57.051 mV/pH and linearity over the pH range of 1.5–12.5 were obtained for the developed MnO2/GPLE pH sensor. The prepared sensor represented high ion selectivity to mono-valence and multi-valence ions with $$- \log K_{{{\text{A}},{\text{B}}}}^{{{\text{Pot}}}}$$ values around 6.49. A fast response time of 20 s in acidic medium and 60 s in alkaline medium, long-term stability and reproducibility in 2 months, the simplicity of fabrication, low cost and accuracy makes this sensor as a suitable choice for rapid pH recording in micro volume samples. The MnO2/GPLE pH sensor was successfully used for the pH monitoring of human tear, human blood, saliva, apple juice, lemon juice, milk, and vinegar samples with satisfactory results.

Ca2+ detection utilising AlGaN/GaN transistors with ion-selective polymer membranes

We demonstrate highly selective and sensitive potentiometric ion sensors for calcium ion detection, operated without the use of a reference electrode. The sensors consist of AlGaN/GaN heterostructure-based transistor devices with chemical functionalisation of the gate area using poly (vinylchloride)-based (PVC) membranes having high selectivity towards calcium ions, Ca2+. The sensors exhibited stable and rapid responses when introduced to various concentrations of Ca2+. In both 0.01 M KCl and 0.01 M NaCl ionic strength buffer solutions, the sensors exhibited near Nernstian responses with detection limits of less than 10−7 M, and a linear response range between 10−7–10−2 M. Also, detection limits of less than 10−6 M were achieved for the sensors in both 0.01 M MgCl2 and 0.01 M LiCl buffer solutions. AlGaN/GaN-based devices for Ca2+ detection demonstrate excellent selectivity and response range for a wide variety of applications. This work represents an important step towards multi-ion sensing using arrays of ion-selective field effect transistor (ISFET) devices.

Liquid membrane/polyaniline film coated glassy carbon sensor for highly sensitive and selective determination of fluvoxamine in pharmaceutical and biological samples

A novel and very sensitive potentiometric sensor with excellent electrochemical properties was fabricated for the determination of fluvoxamine. The sensor is based on the use of the PVC-membrane containing ion-association complex of fluvoxamine with reinecke salt coated on the glassy carbon electrode which was modified with polyaniline as a conductive polymeric film. The proposed sensor exhibits a Nernstian slope of 58.9mV per decade for fluvoxamine over a wide concentration range of 1.8×10−7–1.3×10−3M, with a low detection limit of 7.8×10−8M. The sensor has a fast response time, excellent reproducibility and long life time. It can be used within the pH range of 4.0–7.5 in a long time period. The sensor possesses a high selectivity toward a large variety of inorganic and organic co-existing species. The effect of temperature on the sensor potential response was studied and the isothermal coefficient of the sensor was calculated. The sensor has a good thermal stability within the studied temperature range. The developed sensor was used as an indicator electrode in potentiometric titration of fluvoxamine with sodium tetraphenylborate. The sensor was successfully applied in the determination of fluvoxamine in pharmaceutical solution, blood serum and urine samples.

Potentiometric sensor fabrication having 2D sarcosine memories and analytical features

In this study, a simple, rapid and sensitive method based on novel molecular imprinted polymeric sensor has been developed and validated for the determination of prostate cancer metabolite biomarker. The molecularly imprinted polymer (MIP) has been synthesized by emulsion polymerization, using sarcosine as template molecule, methacryloylamido histidine (MAH) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The performance of the developed sarcosine sensor has been evaluated, and the results have indicated that a sensitive potentiometric sensor has been fabricated. The sarcosine sensor has showed high-selectivity, shorter response time (<2min), wider linear range (10−2–10−6mM), lower detection limit (1.35×10−7mM), and satisfactory long-term stability (>5.5months).

Highly sensitive potentiometric sensors for thorium ions detection using morpholine derivative self-assembled on silver nanoparticles

Potentiometric screen-printed electrodes were constructed for Th(iv) determination in water samples. The optimized electrodes exhibited fast response time, wide linear range, low detection limit and high selectivity towards Th(iv) ions.

Nano anti-tumor necrosis factor-alpha based potentiometric sensor for tumor necrosis factor-alpha detection

Tumor necrosis factor (TNF)-α promotes rheumatoid arthritis (RA) symptoms, including inflammation and bone erosion. The role of TNF-α in RA is considered to be complex because cytokine is responsible for a wide-range of functions, such as activation of immune cells, stimulation of osteoclast differentiation, and induction of cellular apoptosis. It has appeared that the determination of TNF-α concentration in serum might be helpful in the staging and prognosis of diseases. In this study, a simple and sensitive potentiometric sensor method has described for the determination of TNF-α in serum. Influences of the membrane composition, concentration and equilibrium time have been investigated on the response properties of the electrode. The sensor has exhibited a visibly enhanced response toward TNF-α over the concentration range of 0.1–1.0mgL−1 with a lower detection limit (LDL) of 0.015mgL−1 and a slope of 62.2mV decade−1. The sensor has demonstrated a quick and reliable response, ability to be reproduced, as well as long-term stability.

Highly sensitive potentiometric sensor for detection of mercury in Cl−-rich samples

Potentiometric sensors have been exploited for the determination of Hg2+ ions. However, applications of such sensors are limited to mercury detection in the absence of a Cl−-rich background since Hg2+ can readily form coordination complexes with Cl−. This paper describes a potentiometric sensor for the determination of anionic mercury species using tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) as anion-selective ionophore and tridodecylmethylammonium chloride as ion exchanger. An asymmetric membrane rotating ion-selective electrode configuration is used to improve the detection sensitivity. By using HgCl3− as a model of anionic mercury species, the proposed method allows potentiometric detection of mercury down to nanomolar levels in samples containing 0.05M NaCl background electrolyte. The practical application of the proposed sensor has been performed for the determination of total mercury concentrations in diluted seawater samples.

Filmes de polipirrol aplicados no desenvolvimento de eletrodos descartáveis seletivos a íons fluoreto

O presente manuscrito descreve o desenvolvimento de um sensor descartável sensível e seletivo baseado em filmes de polipirrol dopados (PPy) para determinação íons fluoreto. Os íons fluoretos foram incorporados na matriz PPy durante a polimerização eletroquímica realizada em condições galvanostáticas em um eletrodo compósito etileno vinil acetato e negro de fumo. Parâmetros experimentais envolvidos na preparação de película PPy tais como densidade de corrente elétrica, carga elétrica, o pH e a concentração de eletrólito foram otimizados de forma a maximizar a resposta potenciométrica. A resposta do sensor para íons de flúor foi linear no intervalo de concentração de 1,00 × 10- 5 a 1,08 × 10- 2 mol L- 1, com uma inclinação de ~ 40 mV / pF e foi estável suficiente para várias determinações. O método foi aplicado com sucesso na determinação de íons fluoreto em amostras comerciais farmacêuticas. Os resultados demonstraram que o sensor proposto pode ser utilizado como uma alternativa interessante aos métodos analíticos tradicionais para determinação de íons fluoreto.

Reporter-Free Potentiometric Sensing of Boronic Acids and Their Reactions by Using Quaternary Ammonium Salt-Functionalized Polymeric Liquid Membranes

The tremendous applications of boronic acids (BAs) in chemical sensing, medical chemistry, molecular assembly, and organic synthesis lead to an urgent demand for developing effective sensing methods for BAs. This paper reports a facile and sensitive potentiometric sensor scheme for heterogeneous detection of BAs based on their unexpected potential responses on quaternary ammonium salt-doped polymeric liquid membranes. (11)B NMR data reveal that a quaternary ammonium chloride can trigger the hydrolysis of an electrically neutral BA in an aprotic solvent. Using the quaternary ammonium salt as the receptor, the BA molecules can be extracted from the sample solution into the polymeric membrane phase and undergo the concomitant hydrolysis. Such salt-triggered hydrolysis generates H(+) ions, which can be coejected into the aqueous phase with the counterions (e.g., Cl(-)) owing to their high hydrophilicities. The perturbation on the ionic partition at the sample-membrane interface changes the phase boundary potential and thus enables the potentiometric sensing of BAs. In contrast to other transduction methods for BAs, for which labeled or separate reporters are exclusively required, the present heterogeneous sensing scheme allows the direct detection of BAs without using any reporter molecules. This technique shows superior detection limits for BAs (e.g., 1.0 × 10(-6) M for phenylboronic acid) as compared to previously reported methods based on colorimetry, fluorimetry, and mass spectrometry. The proposed sensing strategy has also been successfully applied to potentiometric indication of the BA reactions with hydrogen peroxide and saccharides, which allows indirect and sensitive detection of these important species.