Oxidation Of Epinephrine Research Articles

Fabrication of a nanostructure-based electrochemical sensor for simultaneous determination of epinephrine and tryptophan

A carbon-paste electrode modified with vinylferrocene and carbon nanotubes (CNTs) was used for the sensitive and selective voltammetric determination of epinephrine. The mediated oxidation of epinephrine at the modified electrode was investigated by cyclic voltammetry (CV). Square wave voltammetry (SWV) of epinephrine at the modified electrode exhibited two linear dynamic ranges with a detection limit of 3.0×10−8M. SWV was used for simultaneous determination of epinephrine and tryptophan at the modified electrode, and quantitation of epinephrine and tryptophan in some real samples by the standard addition method.

Spectrophotometric investigation on the kinetics of oxidation of adrenaline by dioxygen of μ-dioxytetrakis(histidinato)-dicobalt(II) complex

The cobalt(II)histidine complex binds molecular oxygen reversibly to form an oxygen adduct complex, μ-dioxytetrakis-(histidinato)dicobalt(II). The molecular oxygen can be released from the oxygenated complex by heating it or by passing N2, He or Ar gas through its solution. μ-Dioxytetrakis-(histidinato)dicobalt(II) complex oxidizes adrenaline into leucoadrenochrome at 25°C while at higher temperature (>40°C) adrenochrome with λmax at 490nm is formed. The rate of formation of leucoadrenochrome was found to be independent of [bis(histidinato)cobalt(II)]. The rate of reaction for the formation of leucoadrenochrome and adrenochrome increased with the increase in [adrenaline] at its lower concentration but become independent at higher concentration. Similarly, the rate of formation of both leucoadrenochrome and adrenochrome was linearly dependent upon [NaOH]. The values of activation parameters i.e. ΔEa, ΔH‡ and ΔS‡ for the formation of leucoadrenochrome are reported.

Electrocatalytic activity of gold modified with gold nanoparticles and self-assembled layers of meso-2,3-dimercaptosuccinic acid for oxidation of epinephrine in the presence of ascorbic and uric acids

Gold electrodes modified successively with gold nanoparticles (Au-NPs), meso-2,3-dimercaptosuccinic acid (DMSA) and cysteamine (CA)/Au-NPs layers were applied for quantitative determination of epinephrine (EP) in the absence or the presence of ascorbic acid (AA) and uric acid (UA) in aqueous electrolyte solutions. The cyclic voltammograms (CVs) and differential pulse voltammograms (DPVs) proved the highest catalytic activity of the Au/Au-NPs/DMSA/CA/Au-NPs electrode for the oxidation of EP as well as for AA and UA. The respective current peaks were clearly separated from each other enabling selective detection of all these compounds coexisting in a mixture, e.g. in physiological samples. For this novel sensor a linear relationship between the current response of EP at the potential of peak maximum (jp) and the concentration of this compound in solution (cEP) was found over the range 0.0001mmol dm−3 to 0.8mmol dm−3 with the detection sensitivity jp/cEP equal to about 7 A cm−2mol−1 dm3 (at v=100mV s−1) and the detection limit of 2.8 10−5mmol dm−3.

NiFe2O4nanoparticles decorated with MWCNTs as a selective and sensitive electrochemical sensor for the determination of epinephrine using differential pulse voltammetry

A new electrochemical method was developed for epinephrine detection based on NiFe2O4–MWCNT-modified electrode. The nanocomposite has a synergic effect on the oxidation of epinephrine.

Highly selective determination of ascorbic acid, epinephrine, and uric acid by differential pulse voltammetry using poly(Adizol Black B)-modified glassy carbon electrode

A polymerized film of Adizol Black B (ABB) on the surface of glassy carbon (GC) electrode was prepared for the simultaneous determination of ascorbic acid (AA), epinephrine (EP), and uric acid (UA). This new electrode presented an excellent electrocatalytic activity towards the oxidation of AA, EP, and UA by differential pulse voltammetry method. The oxidation peaks of the three compounds were well defined and had the enhanced peak currents. The separation of the oxidation peak potentials for AA–EP and EP–UA were about 180 and 130 mV, respectively. The calibration curves obtained for AA, EP, and UA were in the ranges of 2.0–1,970.0, 0.1–64.0, and 0.1–1,700.0 μmol L–1, respectively. The detection limits (S/N = 3) were 0.01, 0.007, and 0.02 μmol L–1 for AA, EP, and UA, respectively. The diffusion coefficient and the catalytic rate constant for the oxidation reaction of EP at poly(ABB) film-coated GC electrode were calculated as 1.54(±0.10) × 10−4 cm2 s−1 and 4.5 × 103 mol−1 L s−1, respectively. The present method was applied to the determination of EP in pharmaceutical, AA in commercially available vitamin C tablet, and UA in urine samples.

Simple and Efficient Epinephrine Sensor Based on Carbon Nanotube Modified Carbon Film Electrodes

A simple electrochemical sensor for epinephrine (EP) has been developed by modification of a carbon film electrode (CFE) with multiwalled carbon nanotubes (MWCNTs) in a chitosan matrix. Cyclic voltammetry (CV) was employed for the evaluation of the electrochemical oxidation of EP at modified electrodes MWCNT/CFE in different pH electrolytes. Under the optimum conditions (pH 7.0), the MWCNT/CFE electrode showed significant electrocatalytic oxidation of EP: a decrease of about 200 mV in the overpotential and an 11-fold increase in the peak current, compared with the unmodified CFE. Detection of EP was carried out by CV, fixed potential amperometry, and differential pulse voltammetry (DPV); the most sensitive response with the lowest detection limit of 0.9 µM obtained by DPV with preconcentration. At MWCNT/CFE, a separation of 175 mV between EP and ascorbic acid peaks was found. The sensor exhibited excellent stability over a period of 6 months and was successfully applied to the analysis of injectable adrenaline solutions.

Human colon adenocarcinoma HT-29 cell: Electrochemistry and nicotine stimulation

Recently, it was demonstrated that colorectal cancer HT-29 cells can secrete epinephrine (adrenaline) in an autocrine manner to auto-stimulate cellular growth by adrenoreceptors activation, and that this secretion is enhanced by nicotine, showing an indirect relation between colorectal cancer and tobacco. The electrochemical behaviour of human colon adenocarcinoma HT-29 cells from a colorectal adenocarcinoma cell line, the hormone and neurotransmitter epinephrine, and nicotine, were investigated by cyclic voltammetry, using indium tin oxide (ITO), glassy carbon (GC) and screen printed carbon (SPC) electrodes. The oxidation of the HT-29 cells, previously grown onto ITO or SPC surfaces, followed an irreversible oxidation process that involved the formation of a main oxidation product that undergoes irreversible reduction, as in the epinephrine oxidation mechanism. The effect of nicotine stimulation of the HT-29 cells was also investigated. Nicotine, at different concentration levels 1, 2 and 15mM, was introduced in the culture medium and an increase with incubation time, 0 to 3h and 30min, of the HT-29 cells oxidation and reduction peaks was observed. The interaction of nicotine with the HT-29 cells stimulated the epinephrine secretion causing an increase in epinephrine release concentration, and enabling the conclusion that epinephrine and nicotine play an important role in the colorectal tumour growth.

Multi-walled carbon nanotube modified carbon paste electrode as an electrochemical sensor for the determination of epinephrine in the presence of ascorbic acid and uric acid

A biocompatible electrochemical sensor for selective detection of epinephrine (EP) in the presence of 1000-fold excess of ascorbic acid (AA) and uric acid (UA) was fabricated by modifying the carbon paste electrode (CPE) with multi-walled carbon nanotubes (MWCNTs) using a casting method. The electro-catalytic activity of the modified electrode for the oxidation of EP was investigated. The current sensitivity of EP was enhanced to about five times upon modification. A very minimum amount of modifier was used for modification. The voltammetric response of EP was well resolved from the responses of AA and UA. The electrochemical impedance spectroscopic (EIS) studies reveal the least charge transfer resistance for the modified electrode. The AA peak that is completely resolved from that of EP at higher concentrations of AA and the inability of the sensor to give an electrochemical response for AA below a concentration of 3.0×10−4M makes it a unique electrochemical sensor for the detection of EP which is 100% free from the interference of AA. Two linear dynamic ranges of 1.0×10−4–1.0×10−5 and 1.0×10−5–5.0×10−7M with a detection limit of 2.9×10−8M were observed for EP at modified electrode. The practical utility of this modified electrode was demonstrated by detecting EP in spiked human blood serum and EP injection. The modified electrode is highly reproducible and stable with anti fouling effects.

Simultaneous determination of ascorbic acid, epinephrine and uric acid at over-oxidized poly(p-aminophenol) film modified electrode

A modified electrode was fabricated by over-oxidation of polymer film after electropolymerization of p-aminophenol on a bare glassy carbon surface. A higher catalytic activity was obtained for electrocatalytic oxidation of ascorbic acid (AA), epinephrine (EN), and uric acid (UA) in pH 7.4 phosphate buffer solution (PBS) at over oxidized poly(p-aminophenol) film modified glassy carbon electrode (Ox-PAP/GCE) due to an enhanced peak current and well-defined peak separations compared with both bare glassy carbon electrode (GCE) and poly(p-aminophenol) film modified GCE (PAP/GCE). The electrode surfaces were characterized by scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM). Individual and simultaneous determination of AA, EN, and UA were carried out by differential pulse voltammetry. The detection limits were individually calculated for ascorbic acid, epinephrine, and uric acid as being 1.0×10−6M, 6.5×10−9M, and 1.8×10−7M, respectively.

Kinetic studies on the manganese(II) complex catalyzed oxidation of epinephrine

The manganese complex [Mn2(HL)2](BPh4)2 was found to be a selective catalyst for the oxidation of epinephrine (a catecholamine derivative) to adrenochrome at room temperature in sodium carbonate–bicarbonate buffer. The epinephrine auto-oxidation rate significantly increases upon the addition of manganese complex. The kinetics of reaction was studied by spectrophotometric method, monitoring the increase in concentration of adrenochrome product. According to the proposed mechanism, O2 binding to the manganese complex is followed by the formation of a ternary catalyst–dioxygen–substrate complex as active intermediate, which decomposes in a rate-determining step, generating the adrenochrome.

Simultaneous determination of adrenaline, uric acid, and cysteine using bifunctional electrocatalyst of ruthenium oxide nanoparticles

Abstract In this study, ruthenium oxide nanoparticles were electrochemically deposited on the surface of a glassy carbon electrode (RuON-GCE). Electrochemical studies indicate that a modified electrode (RuON-GCE) plays the role of an excellent bifunctional electrocatalyst for the oxidation of adrenaline (AD) and uric acid (UA) in two different potentials. The charge transfer coefficient (α) and the heterogeneous charge transfer rate constant ( k ′) between the analytes and the electrodeposited nanoparticles were determined using cyclic voltammetry experiments. Through a different pulse voltammetric (DPV) method, the plot of the electrocatalytic current versus AD and UA concentrations emerged to be constituted of two linear segments with different sensitivities. Furthermore, the detection limits of AD and UA were estimated. In DPV, RuON-GCE could separate the oxidation peak potentials of AD, UA, and cysteine (Cys) present in the same solution though, at the bare GCE, the peak potentials were indistinguishable. Finally, the modified electrode activity was studied for the electrocatalytic determination of AD in an injection solution and UA in a human urine sample. The results were found satisfactory.

Studies on Oxidation of Adrenaline Using Encaged FePc in Y Zeolite as Catalyst

The oxidation of adrenaline (AD) using iron phthalocyanine encaged in Y zeolite (FePc/Y) as catalyst was investigated by UV-Vis spectroscopic analysis. The influence factors of catalytic efficiency, such as catalytic time and temperature, the pH value of solution and the amount of FePc/Y, have been investigated. The results indicated that AD could be effectively catalyzed by FePc/Y.

Biosensor based on tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode for detection of epinephrine

A biosensor comprising tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode has been developed. The sensitive element, ie, tyrosinase, was immobilized using a drop-and-dry method followed by cross-linking. Tyrosinase maintained high bioactivity on this nanomaterial, catalyzing the oxidation of epinephrine to epinephrine-quinone, which was electrochemically reduced (−0.07 V versus Ag/AgCl) on the biosensor surface. Under optimum conditions, the biosensor showed a linear response in the range of 10–110 μM. The limit of detection was calculated to be 2.54 μM with a correlation coefficient of 0.977. The repeatability, expressed as the relative standard deviation for five consecutive determinations of 10−5 M epinephrine solution was 3.4%. A good correlation was obtained between results obtained by the biosensor and those obtained by ultraviolet spectrophotometric methods.

Electrosynthesis of an imidazole derivative and its application as a bifunctional electrocatalyst for simultaneous determination of ascorbic acid, adrenaline, acetaminophen, and tryptophan at a multi-wall carbon nanotubes modified electrode surface

In this research, the electrosynthesis of 4-(1H-benzo[d]imidazol-2-ylthio)-5-methylbenze-1,2-diol (as an imidazole derivative) is reported. An imidazole derivative multi-wall carbon nanotube modified glassy carbon electrode (IMWCNT–GCE) was constructed and used as an excellent bifunctional electrocatalyst for oxidation of ascorbic acid (AA) and adrenaline (AD). Cyclic voltammetry was used to calculate the surface electron transfer rate constant, ks, and the electron transfer coefficient, α, for the electron transfer between MWCNT−GCE and the electrodeposited imidazole derivative. The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous rate constant, k', for the oxidation of AA and AD at the IMWCNT–GCE surface were estimated. The modified electrode was found quite effective for the simultaneous determination of AA, AD, acetaminophen (AC), and tryptophan (Trp) in a mixture solution. The detection limits of AA and AD were calculated as 0.96μM and 0.38μM, respectively. Finally, IMWCNT–GCE was satisfactorily used for the determination of AA, AD, and AC in pharmaceutical samples.

Synthesis and characterization of ordered mesoporous carbon as electrocatalyst for simultaneous determination of epinephrine and acetaminophen

In this research, we report an easy method for synthesis of ordered mesoporous carbon (OMC) with hexagonal arrays of tubes (CMK-5). The synthesized OMC was characterized using X-ray diffraction (XRD), scanning electronic microscopy (SEM) and nitrogen sorption isotherms techniques. Due to the large surface area and high conductivity of OMC, OMC-modified glassy carbon (OMCs/GC) electrode was prepared. The unique electrochemical activity of OMCs/GC electrode was illustrated using cyclic voltammetry (CV) and electron impedance spectroscopy (EIS) in which OMC showed a faster electron transfer rate, as compared with glassy carbon electrode. The electrochemical behavior of epinephrine (EN) and acetaminophen (AP) at OMC/GC electrode was also investigated using cyclic voltammetry. The OMC/GC electrode exhibited high electrocatalytic activities toward oxidation of EN and AP and displayed good voltammetric peak separation between them. In differential pulse voltammetry technique, both EN and AP give sensitive oxidation peaks at 120 mV and 320 mV, respectively. Therefore, investigated method was applied for simultaneous determination of EN and AP. AP and EN give linear response over the range of 0.2–15 μM and 4–100 μM, respectively. The lower detection limits were found to be 0.07 μM for AP and 0.94 μM for EN.

MCM/ZrO2 nanoparticles modified electrode for simultaneous and selective voltammetric determination of epinephrine and acetaminophen

A novel MCM/ZrO2 nanoparticles modified carbon paste electrode (MZ-CPE) was fabricated and used to study the electro oxidation of epinephrine (EP) and acetaminophen (AC) and their mixtures by electrochemical methods. The modified electrode showed electrocatalytic activity toward EP and AC oxidation with a decrease of the overpotential by 173 mV to a less positive potential for EP at the surface of the MZ-CPE and an increase in peak current at pH 7.0. Differential pulse voltammetry peak currents of EP and AC increased linearly with their concentrations in the ranges of 1.0 × 10−6–2.5 × 10−3 and 1.0 × 10−6–2.0 × 10−3 M, respectively, and the detection limits for EP and AC were 5.0 × 10−7 and 4.5 × 10−7 M, respectively.

Electrochemical sensor for epinephrine based on a glassy carbon electrode modified with graphene/gold nanocomposites

A solution-based approach of chemical co-reduction of Au (III) and graphene oxide (GO) was used to prepare graphene/Au (GR/Au) nanocomposites. The gold nanoparticles (nano-Au) integrated in GR acted as spacers for inhibiting the aggregation of GR sheets. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) results revealed that nano-Au particles were dispersed uniformly on the GR sheets. The obtained GR/Au nanocomposites modified glassy carbon electrode (GR/Au/GCE) exhibited high sensitivity in the detection of epinephrine (EP). It has been found that oxidation of EP at this modified electrode occurred at less positive potentials than on bare GCE. The anodic peak current observed were directly proportional to EP concentration between the range of 5.0×10−8 and 8.0×10−6molL−1 (L.O.D.=7.0×10−9molL−1). In addition, the oxidation peaks of EP and ascorbic acid (AA) were separated from each other by approximately 180mV. Therefore the GR/Au nanocomposites modified electrode successfully differentiates the signals of the two analytes. At the same time, this electrode also showed favorable electrocatalytic activity toward some other small biomolecules (such as dopamine, β-nicotinamide adenine dinucleotide, and uric acid), suggesting the potential applications of GR/Au nanocomposites for constructing biosensors.

Selective Determination of Epinephrine in the Presence of Ascorbic Acid Using a Glassy Carbon Electrode Modified with Graphene

A graphene-modified glassy carbon electrode was fabricated via a drop-casting method, and applied to the electrochemical detection of epinephrine. The capacity of the graphene-modified glassy carbon electrode for the selective detection of epinephrine was confirmed in a sufficient amount of ascorbic acid (2 mmol L(-1)) by cyclic voltammetry. The modified electrode showed an excellent electrocatalytical effect on the oxidation of epinephrine. A pair of well-defined redox waves were observed in voltammograms of epinephrine in a phosphate buffered solution (pH 4.0). The peak potentials of epinephrine remained unchanged, and the oxidation peak currents showed a linear relation versus the epinephrine concentration in the range of 3.85 × 10(-7) - 1.31 × 10(-5) mol L(-1) and 1.31 × 10(-5) - 1.09 × 10(-4) mol L(-1) with a correlation coefficient as follows: i(pa1) = -4.25 × 10(-6) - 1.99c (mol L(-1)), R(1) = 0.9953; i(pa2) = -4.31 × 10(-5) - 0.315c (mol L(-1)), R(2) = 0.9988. Detection limit is estimated to be 8.9 × 10(-8) mol L(-1). Graphene-modified glassy carbon electrode was applied to epinephrine sample analysis, and the results were in good agreement with the standard values.

Immobilization of DNA on a glassy carbon electrode based on Langmuir–Blodgett technique: application to the detection of epinephrine

A double-stranded (ds) DNA-octadecylamine Langmuir–Blodgett film was attached to the surface of glassy carbon electrode (GCE) to create a novel voltammetric sensor (DNA-LB/GCE) for epinephrine (EP). Atomic force microscopy and electrochemical impedance spectroscopy were employed to study the characteristic of the DNA-LB film. The electrochemical behavior of EP at the modified electrode was investigated in pH 6.0 phosphate buffer solutions by cyclic voltammetry and amperometric methods. Compared with bare GCE, the DNA-LB/GCE sensor demonstrated an electrocatalytic effect on the oxidation of EP. In addition, the sensor shows excellent selectivity for EP detection, being free of interference from excess ascorbic acid and uric acid, and the method was also applied successfully to detect EP in the human urine samples.

Application of a modified carbon nanotube paste electrode for simultaneous determination of epinephrine, uric acid and folic acid

A novel 5-amino-3′,4′- dimethoxy-biphenyl-2-ol (5ADMB) modified carbon nanotube paste electrode (5ADMBCNPE) was first prepared for the determination of epinephrine (EP). Cyclic voltammetry (CV) was used to investigate the electrochemical properties of the proposed electrode towards the oxidation of EP. It has been found that under an optimum condition (pH 7.0), the oxidation of EP at the surface of the modified electrode occurs at a potential of about 160 mV less positive than that of an unmodified carbon paste electrode. The diffusion coefficient (D = 1.18 × 10−5 cm2 s−1), and electron transfer coefficient (α = 0.53) of EP at the surface of 5ADMBCNPE were determined using electrochemical approaches. Using square wave voltammetry (SWV) a linearity between the oxidation peak current and the EP concentration was obtained in the range of 0.4 to 900.0 μM with a detection limit (3σ) of 88.0 nM. Also, SWV was used for simultaneous determination of EP, uric acid (UA) and folic acid (FA) at the modified electrode.