A novel screen-printed potentiometric electrode with carbon nanotubes/polyaniline transducer and molecularly imprinted polymer for the determination of nalbuphine in pharmaceuticals and biological fluids

Copper levels in biological fluids are associated with Wilson's, Alzheimer's, Menke's, and Parkinson's diseases, making them good biochemical markers for these diseases. This study introduces a miniaturized screen-printed electrode (SPE) for the potentiometric determination of copper(II) in some biological fluids. Manganese(III) oxide nanoparticles (Mn2O3-NPs), dispersed in Nafion, are drop-casted onto a graphite/PET substrate, serving as the ion-to-electron transducer material. The solid-contact material is then covered by a selective polyvinyl chloride (PVC) membrane incorporated with 18-crown-6 as a neutral ion carrier for the selective determination of copper(II) ions. The proposed electrode exhibits a Nernstian response with a slope of 30.2 ± 0.3mV/decade (R2 = 0.999) over the linear concentration range 5.2 × 10-9 - 6.2 × 10-3mol/l and a detection limit of 1.1 × 10-9mol/l (69.9ng/l). Short-term potential stability is evaluated using constant current chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). A significant improvement in the electrode capacitance (91.5 μF) is displayed due to the use of Mn2O3-NPs as a solid contact. The presence of Nafion, with its high hydrophobicity properties, eliminates the formation of the thin water layer, facilitating the ion-to-electron transduction between the sensing membrane and the conducting substrate. Additionally, it enhances the adhesion of the polymeric sensing membrane to the solid-contact material, preventing membrane delamination and increasingthe electrode's lifespan. The high selectivity, sensitivity, and potential stability of the proposed miniaturized electrode suggests its use for the determination of copper(II) ions in human blood serum and milk samples. The results obtained agree fairly well with data obtained by flameless atomic absorption spectrometry.

Abstract2,4,6‐trichlorophenol (TCP) is regarded as a very harmful persistent organic pollutant. It is prohibited by the US EPA due to its stability, possible toxicity, and substantial carcinogenicity, which could result in long‐term harm to both the environment and living things. A novel solid‐contact electrode (SCE) is fabricated and characterized for potentiometric determination of 2,4,6‐trichlorophenol (2,4,6‐TCP). Molecularly imprinted trichlorophenol polymer (MIP) beads are used as a recognition receptor for potentiometric determination of this persistent organic pollutant. The MIPs are synthesized using 4‐vinyl pyridine (4‐VP) and N,N′‐Methylene bis(acrylamide) (N,N‐MBAA) as functional monomer and cross‐linking agent, respectively. They are embedded in a selective polyvinyl chloride (PVC) membrane on the top of multi‐walled carbon nanotubes (MWCNTs), which is used as an ion to electron transducer. The SCE exhibits a Nernstian response with a slope of −55.4±2.1 mV/decade (R2=0.999) over the concentration range of 8.0×10−6 to 1.0×10−4 M, a detection limit of 5.0×10−7 M (0.98 μg/mL), and a response time of <10 s. Using electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP), the suggested SCE′s interfacial capacitance is measured. The interfacial capacitance was increased using MWCNTs and reached 39.7 μF. Also, it prevented the undesirable thin water layer from forming between the conducting glassy carbon (GC) substrate and the sensing membrane. As a result, potential stability is improved, and membrane delamination is avoided. The suggested SCE had a wide range of applications for monitoring TCP in various environmental samples because of the high selectivity, sensitivity, and possible stability that were attained.

Determination of silver ions in distilled water by stripping voltammetry at a Nafion-coated gold electrode in combination with quartz crystal microbalance and electrochemical impedance spectroscopy

The paper presents the design of an all-solid-state portable reference electrode based on a screen-printed carbon paste electrode suitable for rapid human serum testing. The electrode was covered by electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) as an internal solid contact layer and polyvinyl chloride (PVC) membrane containing lipophilic anion and cation additives. The electrochemical properties of PEDOT(PSS) and PEDOT(PSS)/PVC film on a carbon paste electrode were studied by electrochemical impedance spectroscopy and cyclic voltammetry methods. The reference electrode exhibited good potential stability (for H+, Na+, K+, Ca2+, Cl− and CO2 −3/HCO−3), good reproducibility and long-term stability. The structure is applied as reference electrodes in human serum pH analysis with pH ion selective planar electrodes, forming a serum pH sensor. The response time of such a pH sensor was 15 s and the sensitivity was −52.2 ± 1.0 mV per decade. Other properties, such as repeatability, reproducibility and stability, were also evaluated. Clinical trials were carried out and compared with the results obtained from the routine hospital electrolyte analyzer, which demonstrated that their analytical performance was closely matched.

Chitosan-assisted self-assembly of flower-shaped ε-Fe2O3 nanoparticles on screen-printed carbon electrode for Impedimetric detection of Cd2+, Pb2+, and Hg2+ heavy metal ions in various water samples

A new potentiometric method based on the screen-printed ion-selective electrode (SPISE) was described for the determination of Bi(III) ion in different authentic samples. The novelty is based on, for the first time, the utilization of the cerium zirconium phosphotungstate (CZPT) in a screen-printed electrode (SPE) as a sensing material. In the literature, there is no screen-printed ion-selective electrode for the determination of Bi(III) ion. The influences of the paste composition, different conditioning parameters and foreign ions on the electrode performance were investigated. The reversibility and also response time of the electrode have been studied. The electrode showed a Nernstian response of 18.2 mV decade−1 in the concentration range of 3.3 × 10−7–1 × 10−1 mol. L−1. The electrode was found to be usable within the pH range of 3.5–8.0 and exhibited a fast response time, limit of detection (LOD) (1 × 10−7 mol. L−1), limit of quantification (LOQ) (3.33 × 10−7 mol. L−1), long lifetime and good stability. The matched potential method (MPM) was applied to determine the selectivity coefficient. The isothermal temperature coefficient (dEo/dt) of the electrode was calculated. The electrode was successfully applied for the determination of Bi(III) ion in different authentic samples. By comparing the current results with those obtained using inductively coupled plasma optical emission spectrometry, the nominated Bi(III) screen-printed ion-selective electrode has attained acceptable and efficient performance.

Label-free electrochemical impedance immunosensor based on modified screen-printed gold electrodes for the diagnosis of canine visceral leishmaniasis

Homemade screen-printed electrodes (SPEs) were developed using conductive inks based on graphite and alkyd resin. The SPEs were optimized by varying the graphite content (50% and 60% by mass) with the incorporation of toluene (T) as a solvent into the conductive inks to improve homogeneity. The SPEs were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The optimized SPE (SPE 50:50 T) demonstrated higher peak currents and a significant decrease in charge transfer resistance (R ct) from 619 ± 8 Ω to 283 ± 5 Ω compared to the SPE without toluene (SPE 50:50). Additionally, SPE 50:50 T exhibited a more homogeneous surface and an electroactive area 1.4 times larger than that of the SPE 50:50. To enhance sensitivity, SPE 50:50 T was modified with a dispersion of functionalized multiwalled carbon nanotubes (MWCNTs) in ethanol (1 g L−1) and applied to the electroanalytical determination of diuron pesticide (C9H10Cl2N2O). The results showed that the oxidation peak potential was approximately 0.75 V vs. Ag/AgCl in pH 2.0 buffer solution, which is lower than the reported literature value of approximately 1.10 V. The linear concentration range was between 1.07 µmol L−1 and 7.51 µmol L−1 using differential pulse voltammetry (DPV) in pH 2.0 solution, with limits of detection (LOD) and quantification (LOQ) of 0.112 µmol L−1 and 0.373 µmol L−1, respectively. Recovery tests in samples of seawater and grape juice were successfully performed.

Magnetic dispersive solid-phase extraction (MDSPE) is combined with electrochemical detection by using a screen-printed carbon electrode modified with gold nanoparticles to determine lead(II). A zeolite-based magnetic composite was used as sorbent during sample preparation, thus combining the unique properties of zeolites as sorbent materials with the remarkable advantages provided by magnetic materials. Three different zeolite-based magnetic composites were initially investigated and characterized. ZSM-5/Fe2O3 treated with HNO3 (ZSM-5/Fe2O3(tr)) was finally selected as sorbent. Lead was extracted from urine samples using ZSM-5/Fe2O3(tr). After extraction, the phases were separated by using an external magnet. Subsequently, the magnetic composite carrying the analyte was directly deposited onto the working electrode of a modified screen-printed carbon electrode for final electrochemical detection. Thereby, the elution and detection of Pb(II) were carried out in a single step. A multivariate approach was employed to optimize the experimental parameters affecting extraction. Under optimized conditions and at a typical working potential of -0.23V (vs. Ag pseudo-reference electrode), response is linear in the 0 to 25μgL-1 Pb(II) concentration range. The empirical limit of detection ranged from 1.0 to 2.0μgL-1. The method was used to analyze Pb(II)-spiked urine samples, and apparent recoveries ranged between 99 and 107%, with coefficients of variation of <20%. Graphical abstractSchematic presentation of the analytical method to determine lead(II) in urine samples. Magnetic dispersive solid-phase extraction using a zeolite-based composite (ZSM-5/Fe2O3(tr)) is directly combined with electrochemical detection by using a screen-printed carbon electrode modified with gold nanoparticles (SPCnAuE).

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.

Gatifloxacin is the drug of choice in the treatment of community-acquired pneumonia in many studies. However, cytotoxicity was reported at its high doses. Therefore, gatifloxacin overdose monitoring is very important. In this sense, there is a need for developing fast and cheap analytical methods for gatifloxacin quantitation in biological fluids. In the present study, a novel detection strategy involving gatifloxacin quantification in urine samples was developed. The approach has been adapted for the use of solid inner contact and rapid disposal screen-printed graphitic carbon electrodes exhibiting high sensitivity toward gatifloxacin without interference from several ions found in urine samples. The developed electrodes showed linear responses in the concentration ranges from 1 × 10–5 to 0.01 and 1 × 10–6 to 0.01 M for a solid contact glassy carbon ion selective electrode (GSC) and a screen printed electrode (GSP), respectively. The analytical applicability of the approach was demonstrated through recovery experiments of gatifloxacin trace concentrations in urine. GSP ion selective electrode (ISE) was found to have superior stability, shorter response time, higher selectivity and sensitivity and longer shelf life compared to GSC ISE. GSP ISE showed the best Nernestian slope as well as the lowest detection limit. Moreover, the inherent advantages of screen-printed electrodes technology (low sample consumption, low cost and point of care testing) make this methodology very attractive in this field. As a result, the developed ISEs can be the best choice for in-line determination of gatifloxacin in urine samples to detect overdose intake and its associated symptoms as well as for quality-control laboratories without pre-treatment or separation steps.

The current work describes the raising of polyclonal antibodies (pAbs) against domoic acid (DA), an algal toxin produced by the diatom Pseudonitzschia pungens. They were screened for sensitivity and selectivity using a competitive enzyme-linked immunosorbent assay (ELISA). The antiserum produced against a keyhole limpet haemocyanin (DA-KLH) conjugate displayed a high affinity for free DA. The optimized horseradish peroxidase (HRP) ELISA had a detection limit of 0.6 ng mL−1 (ppb) and a working range of 0.8–300 ppb DA applying a streptavidin-biotin amplification system (ABC system). Furthermore this antiserum did not cross-react with similar chemical structures and algal toxins such as kainic acid, aspartic acid, glutamic acid, geranic acid and 2-methyl-3-butenoic acid. When the ELISA was compared using an alkaline phosphatase (AP) label we found the system to behave in a similar manner to the optimized HRP system but the linear range was smaller in the high DA concentration range. These pAbs were then used in the optimization of a screen-printed electrode (SPE) system for measurement of DA. A disposable screen-printed carbon electrode coupled with amperometric detection of p-aminophenol at +300 mV vs. Ag/AgCl, produced by the enzyme AP, was used for signal measurement. The sensor incorporates a relevant range for toxin detection, by which humans become ill (Iverson, F.; Truelove, J. Toxicology and seafood toxins: domoic acid. Natural Toxins 1994, 2, 334–339.) with detection limits achieved at SPE to the order of ppb. The SPE system is simple and cost-effective due to its disposable nature, and analysis time is complete in 30 min. In addition, recovery experiments on DA for both ELISA and SPE highlighted the functionality of these systems yielding a ±12% deviation for the true value for the ELISA using AP and ±25% for the sensor.

This study compares between unmodified carbon paste (CPE; the paste has no ion pair) and polyvinyl chloride (PVC) membrane selective electrodes that were used in potentiometric determination of ketotifen fumarate (KTF), where sodium tetraphenylborate (NaTPB) was used as titrant. The performance characteristics of these sensors were evaluated according to IUPAC recommendations which reveal a fast, stable, and linear response for KTF over the concentration range of 10−7 to 10−2 mol L−1. The electrodes show Nernstian slope value of 52.51 ± 0.20 and 51.51 ± 0.25 mV decade−1 for CPE and PVC membrane electrodes at 30°C, respectively. The potential is nearly stable over the pH range 3.0–6.0 and 2.0–7.0 for CPE and PVC membrane electrodes, respectively. Selectivity coefficient values towards different inorganic cations, sugars, and amino acids reflect high selectivity of the prepared electrodes. The electrodes responses at different temperatures were also studied, and long operational lifetime of 12 and 5 weeks for CPE and PVC membrane electrodes, respectively, were found. These are used for determination of ketotifen fumarate using potentiometric titration, calibration, and standard addition methods in pure samples, its pharmaceutical preparations (Zaditen tablets), and biological fluid (urine). The direct potentiometric determination of KTF using the proposed sensors gave recoveries % of 98.97 ± 0.53 and 98.62 ± 0.74 with RSD 1.42 and 0.63% for CPE and PVC membrane selective electrodes, respectively. Validation of the method shows suitability of the proposed sensors for use in quality control assessment of KTF. The obtained results were in a good agreement with those obtained using the reported spectrophotometric method.

Potentiometric determination of antihistaminic diphenhydramine hydrochloride in pharmaceutical preparations and biological fluids using screen-printed electrode

Detection of the SARS-CoV-2 nucleoprotein by electrochemical biosensor based on molecularly imprinted polypyrrole formed on self-assembled monolayer.