A novel high selective and sensitive metronidazole voltammetric sensor based on a molecularly imprinted polymer-carbon paste electrode

The design and construction of a highly selective voltammetric sensor for metronidazole by using a molecularly imprinted polymer (MIP) as recognition element were introduced. A metronidazole selective MIP and a nonimprinted polymer (NIP) were synthesized and then incorporated in the carbon paste electrodes (CPEs). The sensor was applied for metronidazole determination using cathodic stripping voltammetric method. The MIP-CP electrode showed very high recognition ability in comparison to NIP-CPE. Some parameters affecting the sensor response were optimized and then the calibration curve was plotted. Two dynamic linear ranges of 5.64 × 10⁻⁵ to 2.63 × 10⁻³ mg L⁻¹ and 2.63 × 10⁻³ to 7.69 × 10⁻² mg L⁻¹ were obtained. The detection limit of the sensor was calculated as 3.59 × 10⁻⁵ mg L⁻¹. This sensor was used successfully for metronidazole determination in biological fluids.     

A novel high selective and sensitive para-nitrophenol voltammetric sensor, based on a molecularly imprinted polymer-carbon paste electrode

By using a molecularly imprinted polymer (MIP) as a recognition element, the design and construction of a high selective voltammetric sensor for para-nitrophenol was formed. Para-nitrophenol selective MIP and a non-imprinted polymer (NIP) were synthesized, and then used for carbon paste (CP) electrode preparation. The MIP-CP electrode showed greater recognition ability in comparison to the NIP-CP. It was shown that electrode washing after para-nitrophenol extraction led to enhanced selectivity, without noticeably decreasing the sensitivity. Some parameters affecting sensor response were optimized and a calibration curve was plotted. A dynamic linear range of 8 × 10⁻⁹ to 5 × 10⁻⁶ mol L⁻¹ was obtained. The detection limit of the sensor was calculated as 3 × 10⁻⁹ mol L⁻¹. Thus, this sensor was used successfully for the para-nitrophenol determination in different water samples.     

ZrO2-Graphene-Chitosan nanocomposite modified carbon paste sensor for sensitive and selective determination of dopamine

A sensitive and stable electrochemical sensor was developed by modification of carbon paste electrode with ZrO₂/graphene/chitosan nanocomposite. The modified sensor served as a potential electrocatalytic platform for dopamine. Electrochemical impedance spectroscopy studies indicated reduction of charge transfer resistance at the modified electrode surface thereby facilitating the electron transfer process which resulted in higher current response to dopamine. The electrochemical behavior of dopamine at the modified electrode was studied using cyclic and square wave voltammetry. The maximum current response for the electro-oxidation of dopamine was observed at pH 7.4 and the process was realized to be diffusion controlled. The modified sensor demonstrated linearity in the range 1000–5000 nM, with high sensitivity (22 nA/nM), detection limit of 11.3 nM and selectivity for dopamine in the presence of ascorbic and uric acid which are found to co-exist with dopamine in physiological media. The method was employed for quantification of dopamine in a pharmaceutical formulation.     

Nickel-Zeolite modified carbon paste electrode as electrochemical sensor for hydrogen peroxide

In the present work, nickel-zeolite modified carbon paste electrode (Ni-ZMCPE) was prepared. The electrochemical behaviour of hydrogen peroxide at the surface of modified electrode was investigated by cyclic voltammetry and chronoamperometry in 0.1 M NaOH supporting electrolyte. The electrochemical characterization of Ni-ZMCPE exhibits redox behavior of Ni(III)/Ni(II) couple in alkaline medium. It has been shown that Ni-ZMCPE improves efficiency of the modified electrode toward hydrogen peroxide electrooxidation (It wasn’t remarkable different on ZMCPE and CPE in the presence and absence of hydrogen peroxide). Moreover, the effects of various parameters such as effect of different percents of Ni-Z to graphite, effect of pH and hydrogen peroxide concentration on the electrooxidation of hydrogen peroxide as well as stability of the Ni-ZMCPE have also been investigated. Under the selected conditions, the anodic peak current was linearly dependent on the concentration of hydrogen peroxide in the range 0.03–0.1 and 0.3–6 mM with amperometric method. The detection limit (S/N = 3) was also estimated to be 1 μM.     

The electrochemical oxidation of pentachlorophenol and its sensitive determination at chitosan modified carbon paste electrode

We report on a novel electrochemical method to detect trace pentachlorophenol (PCP) by using a chitosan (CS) modified carbon paste electrode (CS/CPE). Compared with that at a bare carbon paste electrode (CPE), the current response was greatly improved at the CS/CPE due to the enhancement effect of CS. Under optimal working conditions, the oxidation peak current of PCP was proportional to its concentration in the range of 1.0 × 10^?7 to 5.0 × 10^?6 and 5.0 × 10^?6 to 1.0 × 10^?4 mol/L, with an extremely low detection limit of 4.0 × 10^?8 mol/L. Our method was successfully used to detect the PCP concentration in vegetable samples.     

Fluorometric determination of quercetin by using graphitic carbon nitride nanoparticles modified with a molecularly imprinted polymer

The authors describe a fluorescent probe for sensitive and selective determination of quercetin, an indicator for the freshness of drinks. The probe consists of silica ball encapsulated graphitic carbon nitride (g-C₃N₄) modified with a molecularly imprinted polymer (MIP). It was synthesized via reverse microemulsion. The resulting MIP@g-C₃N₄ nanocomposite was characterized by fluorescence spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray powder diffraction. Quercetin quenches the fluorescence of the MIP@g-C₃N₄ probe. The effect was used to quantify quercetin in grape juice, tea juice, black tea, and red wine by fluorometry (λ_exc?=?350 nm, λ_em?=?460 nm). Response is linear in the 10–1000 ng mL^?1 quercetin concentration range. The detection limit is 2.5 ng mL^?1, recoveries range between 90.7 and 94.1%, and relative standard deviations are between 2.1 and 5.5%.

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Graphical abstract Schematic of the synthesis of the MIP@g-C₃N₄ by a reverse microemulsion method. The probe was applied for the selective recognition and fluorometric determination of quercetin.

     

A chemometrics approach for simultaneous determination of cyanazine and propazine based on a carbon paste electrode modified by a molecularly imprinted polymer

In a completely rational and designed approach, simultaneous determination of cyanazine and propazine in environmental and food samples was performed using a molecularly imprinted polymer modified carbon paste electrode (MIP-CPE) and partial least squares. The MIP-CPE designed is based on the theoretical studies functioned as a selective recognition element and pre-concentrator agent for cyanazine and propazine. Fractional factorial and central composite designs were performed to recognize, and subsequently optimize, the variables affecting the cathodic stripping voltammetric currents for the analytes. The important variables were identified to be accumulation potential with optimum values of -0.45 and -0.44 V and pH with optimum values of 2.40 and 2.34 for cyanazine and propazine, respectively. Exploration of the overall optimum conditions for simultaneous determination of cyanazine and propazine resulted in accumulation potential of -0.44 V and pH of 2.4. Dynamic linear ranges of 0.05-9.00 μmol L(-1) and 0.01-1.00 μmol L(-1) and detection limits of 0.010 and 0.001 μmol L(-1) were obtained for cyanazine and propazine, respectively. The results of the application of the proposed method on the simultaneous determination of cyanazine and propazine in foodstuffs and environmental samples were satisfactory.     

Development of a sensitive and selective kojic acid sensor based on molecularly imprinted polymer modified electrode in the lab-on-valve system

In this work, a kojic acid electrochemical sensor, based on a non-covalent molecularly imprinted polymer (MIP) modified electrode, had been fabricated in the lab-on-valve system. The sensitive layer was synthesized by cyclic voltammetry using o-phenylenediamine as the functional monomer and kojic acid as the template. The template molecules were then removed from the modified electrode surface by washing with NaOH solution. Differential pulse voltammetry method using ferricyanide as probe was applied as the analytical technique, after extraction of kojic acid on the electrode. Chemical and flow parameters associated with the extraction process were investigated. The response recorded with the imprinted sensor exhibited a response in a range of 0.01-0.2 μmol L⁻¹ with a detection limit of 3 nmol L⁻¹. The interference studies showed that the MIP modified electrode had excellent selectivity. Furthermore, the proposed MIP electrode exhibited good sensitivity and low sample/reagent consumption, and the sensor could be applied to the determination kojic acid in cosmetics samples.     

A molecularly imprinted polymer-coated nanocomposite of magnetic nanoparticles for estrone recognition

In this study, we synthesized Fe₃O₄ magnetic nanoparticles coated estrone-imprinted polymer with controlled size using a semi-covalent imprinting strategy. In this protocol, the estrone-silica monomer complex (EstSi) was synthesized by the reaction 3-(triethoxysilyl)propyl isocyanate with estrone, where the template was linked to the silica coating on the iron oxide core via a thermally reversible bond. The removal of the template by a simple thermal reaction produced specific estrone recognition sites on the surface of silica shell.The resulting estrone-imprinted polymer coating Fe₃O₄ magnetic hybrid nanoparticles exhibit a much higher specific recognition and saturation magnetization. The hybrid nanoparticles have been used for biochemical separation of estrone.     

A sensitive and selective nitrite sensor based on a glassy carbon electrode modified with gold nanoparticles and sulfonated graphene

We describe a highly sensitive and selective amperometric sensor for the determination of nitrite. A glassy carbon electrode was modified with a composite made from gold nanoparticles (AuNPs) and sulfonated graphene (SG). The modified electrode displays excellent electrocatalytic activity in terms of nitrite oxidation by giving much higher peak currents (at even lower oxidation overpotential) than those found for the bare electrode, the AuNPs-modified electrode, and the SG-modified electrode. The sensor has a linear response in the 10 μM to 3.96 mM concentration range, a very good detection sensitivity (45.44 μA mM^?1), and a lower detection limit of 0.2 μM of nitrite. Most common ions and many environmental organic pollutants do not interfere. The sensor was successfully applied to the determination of nitrite in water samples, and the results were found to be consistent with the values obtained by spectrophotometry.

A glassy carbon electrode modified with graphene nanoplatelets,gold nanoparticles and chitosan,and coated with a molecularly imprinted polymer for highly sensitive determination of prostate specific antigen

Microchimica Acta - The authors describe an amperometric assay for the detection of prostate specific antigen (PSA) that combines the advantages of using a molecularly imprinted polymer (MIP) and...     

A selective modified carbon paste electrode for determination of cyanide using tetra-3,4-pyridinoporphyrazinatocobalt(II)

A chemically modified carbon paste electrode with 3,4-tetra pyridinoporphirazinatocobalt(II) (Co(3,4 tppa) was applied to the determination of free cyanide ion. The electrode has a linear range between 1.5 × 10⁻⁵ M and 1.0 × 10⁻² M with a Nernstian slope of 60 ± 1.5 mV/decade and its detection limit is 9 × 10⁻⁶ M. The response time of electrode is 5 min. The proposed electrode was applied successfully for the determination of cyanide in commercially available spring water. Some anions, such as SCN⁻, I⁻, Cl⁻, Br⁻ and oxalate that are usually serious interfering species for most of cyanide selective electrodes, did not have any interfering effect for this proposed electrode.     

An electrochemical sensor for rapid determination of ractopamine based on a molecularly imprinted electrosynthesized o-aminothiophenol film

A simple electrochemical sensor based on a molecularly imprinted polymer film as the recognition element was developed for ractopamine (RAC) detection. This is the first report of a RAC-imprinted film on a gold electrode surface, synthesized through an electrochemical method using o-aminothiophenol as the functional monomer. The imprinting mechanism and experimental parameters affecting the capability of the imprinted film are discussed here. The sensor was successfully applied with constant potential amperometry for RAC detection in an indirect process with potassium ferricyanide as an electrochemical probe. The sensor had a rapid equilibrium time (120?s), high binding affinity and selectivity towards RAC, and with good reproducibility and stability. Under the experimental conditions applied, a linear relationship between the relative amperometric response and RAC ranged from 2.0?×?10(-7) to 1.4?×?10(-6)?mol?L(-1), with a lower limit of detection (LOD) of 2.38?×?10(-8)?mol?L(-1) (signal to noise ratio?=?3). The sensor was tested with feed samples spiked with trace amounts of RAC, with good recoveries between 87.4 and 90.5?%.     

Highly sensitive and selective voltammetric determination of dopamine using a gold electrode modified with a molecularly imprinted polymeric film immobilized on flaked hollow nickel nanospheres

The authors describe the preparation of a molecularly imprinted polymer (MIP) film on the surface of electrodeposited hollow nickel nanospheres (hNiNS), and the use of this nanocomposite in an electrochemical sensor for dopamine (DA). The use of the 3-dimensional hNiNS as a support material enlarges the sensing area and conductivity, while the MIP film warrants improved selectivity for DA. Quantification based on the “MIP/gate effect” was performed by employing hexacyanoferrate as the electrochemical probe. Scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy were applied to characterize the sensor materials. The electropolymerization condition such as pH value, functional monomer and ratio of template to monomer were optimized. By using dopamine (DA) as a model analyte, the sensor, if operated at 0.1 V vs. SCE, has fairly low detection limit of 1.7?×?10^?14 M (at an S/N ratio of 3), two wide assay ranges of 5?×?10^?14 to 1?×?10^?12 M and 1?×?10^?12 to 5?×?10^?11 M, and superb selectivity.

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Graphical Abstract An electrochemical sensor platform with a novel composite film composed of hollow nickel nanospheres (hNiNS) and molecularly imprinted polymer (MIP) was developed via a facile double-elecrodeposition method. The synergistic effects of hNiNS and MIP guarantee the ultrahigh sensitivity (down to 10^?2 ppt) and selectivity of the sensor.

     

Biomimetic electrochemical sensor based on molecularly imprinted polymer for dicloran pesticide determination in biological and environmental samples

Dicloran pesticide is used to inhibit the fungal spore germination for different crops. Because of the increasing application of pesticides, reliable and accurate analytical methods are necessary. The aim of this work is designing the highly selective sensor to determine the dicloran in biological and environmental samples. Multi-walls carbon nanotubes and a molecularly imprinted polymer (MIP) were used as modifiers in the sensor composition. A dicloran MIP and a nonimprinted polymer (NIP) were synthesized and applied in the carbon paste electrode. After the optimization of electrode composition, it was used to determine the concentration of analyte. Parameters affecting the sensor response were optimized, such as sample pH, electrolyte concentration and its pH, and the instrumental parameters of square wave voltammetry. The MIP-CP electrode showed very high recognition ability in comparison with NIP-CP. The obtained linear range was 1 × 10^?6 to 1 × 10^?9 mol L^?1. The detection limit was 4.8 × 10^?10 mol L^?1. This sensor was used to determine the dicloran in real samples (human urine, tap and river water samples) without special sample preparation before analysis. All important parameters were optimized, improving the sensor response considerably.     

Acetylene black paste electrode modified with a molecularly imprinted chitosan film for the detection of bisphenol A

We report on a voltammetric sensor for bisphenol A (BPA) that is based on an acetylene-black paste electrode modified with a chitosan film molecularly imprinted for BPA. The sensor responds linearly to BPA in the 80 nM to 10 μM concentration range, and the detection limit is 60 nM (at an S/N of 3). The use of a molecular imprint provides an efficient way for eliminating interferences from potentially interfering substances. The high sensitivity, selectivity and stability of the sensor demonstrate its practical application for the determination of BPA in plastic samples.

Electrochemical determination of naproxen in the presence of acetaminophen using a carbon paste electrode modified with activated carbon nanoparticles

In this study, cyclic voltammetry and differential pulse voltammetry were used to determine the electrochemical properties and concentration of naproxen in pharmaceutical formulation and human serum samples by using a carbon paste electrode modified with activated carbon nanoparticles. Optimum conditions were obtained at an electrode with 0.005 g activated carbon nanoparticles in a phosphate buffer solution of pH 6 as a supporting electrolyte. Linear calibration curves were obtained in the range of 0.1–120 μM, and the detection limit of naproxen determined was 0.0234 μM. The modified electrode shows good selectivity for naproxen in the presence of some organic and inorganic interferences and very good precision in real samples. Finally, naproxen was measured in the presence of acetaminophen.