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Successful applications of different analytical procedures to determine quantitatively mercury in aqueous media can be found in recent literature. Fundamentally it has made use of Cold Vapour Atomic Absorption Spectrometry (CV-AAS), X-Ray Fluorescence or UV Spectrophotometry, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), or Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which are the techniques commonly used for trace measurement of heavy metal in the laboratory. In this paper a new and alternative methodology to determine quantitatively mercury in aqueous media is reported. A kryptofix carbon-paste electrode has been used to determine voltammetrically mercury. The detection limit for mercury was evaluated to be 0.12 µg/l. [ABSTRACT FROM AUTHOR]

A film of polypyrrole/γcyclodextrin (PPY/γCD) was synthesized at a gold electrode by the simple electropolymerization of a 1:1 mixture of γCD and pyrrole monomer in aqueous solutions. Different voltammetric behaviors were obtained between PPY/γCD and PPY during the electrosynthesis process. Electrochemical impedance spectroscopy (EIS) was used to characterize the electrical properties of the electropolymerized films. The PPY/γCD films exhibit interesting properties such as a wider potential range for electroanalytical exploration that yields to easier and improved electrochemical detection of neurotransmitters such as dopamine, L-dopa, epinephrine, norepinephrine, and isoproterenol. Well resolved and reversible cyclic voltammograms (CVs) of these organic compounds could be obtained easily at the modified electrode with a negative shift of their oxidation potentials as compared with the response at bare gold electrodes. The plot of the neurotransmitters' catalytic currents vs. their concentrations gave good linear relationship inside the range of 2·10-6–2·10-5 M with R2 = 0.998. Detection limits between 6·10-7 M and 6·10-6 M were obtained for the molecules studied. According to the CV' s scan rate evolution, the electron transfer for the neurotransmitters was mainly diffusion controlled at the polymer-γCD/solution interface. Attempts to use the PPY/γCD sensor on real human serum for L-dopa exploration yield encouraging data. [ABSTRACT FROM AUTHOR]

A simple approach for increasing the sensitivity and selectivity for the detection of mercury(II) species in water is presented. The technique is based on two steps: (1) micro-extraction (uptake step) of mercury(II) by simply incubating an electropolymerized poly(3-methylthiophene) (P3MT) modified gold electrode, at open-circuit potential conditions, into a solution containing the heavy metal for 30 min and (2) the electrode is transferred from the analyte solution to an electrochemical cell (release step) for successive voltammetric determinations. Surprisingly, cyclic voltammetric measurements showed a first large anodic peak characteristic of oxidation of metallic mercury to form mercury(II) at 0.53 V. The reversed scan, showed a smaller cathodic peak at 0.4 V, suggesting a possible electroless reduction from Hg(II) to metallic mercury during the extraction step probably caused by the heteroatom of P3MT. Under these conditions, differential pulse voltammetry (DPV) measurements performed on the P3MT electrode showed that the anodic peak current exhibit a good linear concentration dependence in the range 10−8–4 × 10−6 mol/L. The detection limit was estimated for S/N > 3 to be 10−10 mol/L. The analytical performances of the extraction method has been explored by optimizing the electropolymerization time, pH, and effect of interferences due to other ions. On the other hand, scanning election microscopy–energy dispersive analysis of x-ray (SEM–EDAX) and electrochemical impedance spectroscopy (EIS) measurements performed on P3MT films confirmed the adsorption of the heavy metal on the polymeric film due to the extraction process. [ABSTRACT FROM AUTHOR]

Cancer is one of the most serious diseases that threaten human life. In the last few decades, there was a significant decrease in the death rate in the US due to cardiovascular, cerebrovascular, and infectious diseases, however non-significant alteration in cancer-related mortalities was achieved since 1950 despite the quick improvement in research methodology and technology. Thus, discovering and developing novel methods for the early detection of cancer has a vital importance. The detection of cancer biomarkers plays an important role in clinical diagnoses and evaluation of treatment for patients. Many immunoassay methods are developed for detection of cancer biomarkers. Early detection of cancer biomarkers plays an important role in clinical diagnoses, oncological medicine and evaluation of treatment for patients. Recent and previous research has shown early detection of cancer increases the odds of patient survival. Different methods have been used for tumor marker detection and determination, in the last five years several reports have appeared where intrinsically fluorescent techniques have been used for tumor markers in cancer patients. In this work the first step towards a molecularly imprinted polymer (MIP) based on star fish compounds for the detection of some tumor markers via fluorescence spectroscopic techniques was presented. The interactions of a new synthesized dendrimer compounds with Alpha-fetoprotein and cancer antigens CA15-3 tumor markers have been studied using spectroscopic techniques. [ABSTRACT FROM AUTHOR]

Abstract: The Sonogel–Carbon electrode is a special class of sol–gel electrode that exhibits favourable mechanic and electric properties to be used as electrochemical sensor. In this study, Sonogel–Carbon modified with l-Cysteine was used to prepare a novel electrochemical sensor. The objective of this novel electrode modification was to seek new electrochemical performances for detection of epinephrine in the presence of uric acid. The response of catalytic current with epinephrine concentration shows a linear relation in the range from 1×10−7 to 5×10−4 M with a correlation coefficient of 0.998, and a detection limit of 8.7×10−8 M. The modified electrode had also been applied to the determination of epinephrine and uric acid in biological samples with satisfactory results. A surface characterisation of this modified electrode was carried out helped by scanning electron microscopy (SEM) and X-Ray energy dispersive spectroscopy (EDS). [Copyright &y& Elsevier]

This work presents a significant investigation involving both electrochemical experiment and quantum chemical simulation approaches. The objective was to characterize the electrochemical detection of dopamine (DA). The detection was carried out using a modified carbon paste electrode (CPE) incorporating bentonite (Bent) and l-cysteine (CySH) (named as CySH/Bent/CPE). To understand and explain the oxidation mechanism of DA on the CySH/Bent modified electrode surface, the coupling of the two approaches were exploited. The CySH/Bent/CPE showed excellent electroactivity toward DA such as good sensibility, selectivity, stability, and regenerative ability. The developed sensor shows a dynamic linear range from 0.8 to 80 μM with a limit of detection and quantification of 0.5 μM and 1.5 μM, respectively. During the quantitative analysis of DA in presence of ascorbic acid (AA) and uric acid (UA) the electrochemical oxidation signals of AA, DA, and UA distinctly appear as three separate peaks. The potential differences between the peaks are 190 mv, 150 mv, and 340 mV for the AA-DA, DA-UA, and AA-UA oxidation pairs, respectively. These observations stem from square wave voltammetry (SWV) studies, along with the corresponding redox peak potential separations. The developed sensor is simple and accurate to monitor DA in human serum samples. On the other hand, CySH acts as an electrocatalyst on the CySH/Bent/CPE surface by increasing its active electron transfer sites, as suggested by the quantum chemical modeling with analytical results of Fukui. Furthermore, the voltammetric results obtained agree well with the theoretical calculations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study aims to develop a suitable electrochemical electrode through the incorporation of potassium montmorillonite (MMT K10 )clay into the carbon matrix for the direct and sensitive determination of paracetamol (PAR) in pharmaceutical formulations. Electrochemical characterization of the electrodes involves the use of techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The results reveal that the voltammetric response of PAR is linear over a wide concentration range (1.0-15 μM), with a low detection limit of 0.46 μM. Analytically, PAR recovery results were around 94%, indicating that the developed electrode is highly suitable for PAR detection in pharmaceutical formulation. Additionally, density functional theory (DFT) is employed to investigate the reactivity of PAR and explain the interaction process of PAR on the electrode surface at different pH values. A Monte Carlo simulations model is developed to provide a deeper understanding of the adsorption mechanism, particularly to comprehend molecular interactions and preferential orientations of PAR with MMT fractions at the electrode surface. Reduced Density Gradient is calculated and discussed using techniques such as Multiwfn and Visualization of Molecular Dynamics. The developed CPE-MMT K10 sensor provided a simple preparation method, rapid response, high sensitivity, reproducibility, strong selectivity, and extended stability. Moreover, there is a good correlation between most parameters calculated by DFT and experimental results, thereby reinforcing the validity of the theoretical approach in this study., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A novel modification of a paste carbon electrode by Bentonite (Bent) and l-Cysteine (l-Cyst) was carried out for uric acid (UA) and ascorbic acid (AA) detection and quantification. Morphological and compositional characterization of the electrode surface were carried out using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopic analysis (EDS). Cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques were used to analyze UA and AA. The obtained sensor shows a good stability, sensibility, selectivity, and regeneration ability. Accordingly, the limit of detection (LOD) is found to be 0.031 μm and 9.6 μm for UA and AA, respectively. A good linearity in the range of 0.1 to 100 μm for UA and 10 to 1000 μm for AA was obtained. The peak-to-peak separation of UA-AA (ΔE UA-AA ) was determined to be 330 mV. In addition, the sensor is applied successfully to monitor UA and AA in serum samples., (© 2023 The Authors. Published by Wiley-VCH GmbH.)

Neuroblastoma is a pediatric neuroblastic tumor arising in the sympathetic nervous crest cells. A high grade of Neuroblastoma is characterized by a high urinary excretion of homovanillic acid and dopamine. In this work l-leucine modified Sol-Gel-Carbon electrode was used for a sensitive voltammetric determination of homovanillic acid and dopamine in urine. The electrochemical response characteristics were investigated by cyclic and differential pulse voltammetry; the modified electrode has shown an increase in the effective area of up to 40%, a well-separated oxidation peaks and an excellent electrocatalytic activity. High sensitivity and selectivity in the linear range of 0,4-100μML -1 of homovanillic acid and 10-120μML -1 of dopamine were also obtained. Moreover, a sub-micromolar limit of detection of 0.1μM for homovanillic acid and 1.0μM for the dopamine was achieved. Indeed, high reproducibility with simple preparation and regeneration of the electrode surface made this electrode very suitable for the determination of homovanillic acid and dopamine in pharmaceutical and clinical preparations. The mechanism of homovanillic acid and the electrochemical oxidation at l-leucine modified Sol-Gel-Carbon electrode is described out the B3P86/6-31+G(d,p) level of theory as implemented in Gaussian software., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this work, a new alternative for the electrochemical determination of catecholamines based on beta-cyclodextrin-Sonogel-Carbon electrodes is reported. The incorporation of beta-CD and graphite in the preparation of the Sonogel-Carbon material leads to a modification of the electrode surface properties which causes a significant increase in the oxidation peak current of biomolecules such as dopamine, L-epinephrine, D,L-norepinephrine and catechol. This phenomenon might be attributed to the formation of an inclusion complex between beta-CD and the catecholamines. The amount of beta-CD necessary to form the Sonogel electrode was studied and optimization of electrochemical parameters, perm selectivity and mechanical stability of the sensor are discussed. Scanning electron microscopy and electrochemical impedance spectroscopy measurements were employed to characterize the electrical parameters and the structural properties of the new electrode surface, respectively. Cyclic voltammetry (CV) and Adsorptive differential pulse voltammetry (AdDPV) measurements were also used to explore the electrochemical behaviour of the electrode versus the quoted catecholamines. The beta-CD-Sonogel-Carbon electrode offers fast and linear responses towards dopamine, norepinephrine, epinephrine and catechol, with good and low detection limits: 0.164, 0.294, 0.699 and 0.059 micromol L(-1), respectively.

Gamma-cyclodextrin is an eight glucose unit conical structure, which possesses a hydrophobic internal cavity exhibiting supramolecular complexing properties and a hydrophilic exterior due to the presence of hydroxyl groups. In this work, we have synthesized for the first time a functionalized stable film of poly-3-methylthiophene combined with gamma-cyclodextrin (P3MT/gamma-CD) in tetrabutylammonium hexafluorophosphate/acetonitrile solution. A potentiostatic mode was employed for the film growth. Cyclic voltammetry and electrochemical impedance spectroscopy were used for the characterization of the new film. The resulting conducting polymer sensor offers interesting analytical performances such as: (a) fast and linear responses towards the neurotransmitters dopamine and l-dopa towards the neuroleptic chlorpromazine with low detection limits of 2 x 10(-7), 10(-6), and 10(-7)M, respectively, and (b) simultaneous detection and well-resolved signals between the compounds of interest and ascorbic acid. To the best of our knowledge, these LOD are among the lowest found in the literature. Optimization of parameters such as interference effect, perm-selectivity, and mechanical stability of the sensor are discussed.

The supramolecular complexing properties of cyclodextrins (CDs) have been investigated inside a conducting polymer environment. In this work, we report the synthesis and characterization of a polypyrrole/beta-cyclodextrin (Ppy/beta-CD) film at a glassy carbon (GC) electrode surface. The polypyrrole/beta-cyclodextrin (Ppy/beta-CD) film was prepared by a simple electropolymerization of a 20:1 mixture of the CD and the pyrrole monomer LiClO(4) supporting electrolyte. The resulting functionalized polymer film features interesting electrochemical properties such as selective, simultaneous and quantitative detection of some organic compounds of interest such as polyhydroxyphenyls and neurotransmitters derived from pyrogallol and catechol. The fabricated electrochemical sensor exhibits a fast and reversible linear response toward catechol within the concentration range of 1.5x10(-7) to 8x10(-6)M and towards pyrogallol within the concentration range of 1x10(-6) to 1x10(-5)M. The detection limit was 4x10(-7) and 1.8x10(-6)M for catechol and pyrogallol, respectively. Studies of neurotransmitters such as epinephrine, metanephrine and l-dopa (l-3,4-dihydroxyphenylalanine), showed better response toward epinephrine and l-dopa than for metanephrine. Calibration curves for these two neurotransmitters were linear over the concentration range of 1x10(-6) to 1x10(-5)M. The detection limit was 4x10(-6) and 1x10(-6), respectively. The complexation capability of the Ppy/beta-CD system is addressed here in terms of structure-electrochemical activity relationship. The mechanical stability of the film is also discussed. Measurements were performed using cyclic voltammetry (CV), scanning electron microscopy (SEM) coupled to energy dispersive analysis of X-ray (EDAX) and electrochemical impedance spectroscopy (EIS).