Electro-oxidation Of Uric Acid Research Articles

Oxygen‐Doped Graphitic Carbon Nitride for Electrochemical Uric Acid Sensing: Method Without Metals

AbstractThe present study examined potential benefits of heteroatom doping to manipulate the electrical structure and to enhance the efficiency of the sensor, with an emphasis on developing inexpensive, metal‐free electrochemical sensors. Melamine and ammonium oxalate were used as precursors in a one‐step thermal polymerization technique yielding oxygen‐doped graphitic carbon nitride (O‐gCN). Following synthesis, the material's structural and morphological properties were thoroughly examined using a multitude of analytical techniques, including EIS. A notable decrease in impedance was observed, suggesting improved conductivity. Additionally, the doping approach exhibited a noticeable improvement in reduction current receptivity and surface area as compared to unmodified graphitic carbon nitride (g‐CN). Utilizing both differential pulse voltammetry (DPV) and the classical cyclic voltammetry (CV) methods, we investigated the electro oxidation of uric acid (UA) as well as concentration dependence and selectivity studies using oxygen‐doped graphitic carbon nitride modified glassy carbon electrode (O‐gCN@GCE). O‐gCN@GCE demonstrated remarkable performance, allowing the detection of UA concentrations as low as 7.784 µAµM−1cm−2. Its low detection limit of 0.57 µM and wider linear range (5–120 µM) further highlighted its potential for extremely sensitive assays and its remarkable capacity to operate over a broad UA concentration range.

Nature inspired poly (dopamine quinone -vanadyl) as new modifier for voltammetric determination of uric acid.

Thepreparation of a novel polymer (poly(dopamine quinone-vanadyl) (polyDQV)) bearing dopaminequinone and VOIV redox groupsis described. PolyDQV was characterized using field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy, UV-Vis spectroscopy as well as electrochemical methods such as differential pulse voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The electrocatalytic activity of polyDQV was studied toward electrooxidation of uric acid using differential pulse voltammetry as well as cyclic voltammetry. PolyDQV presents interesting electrocatalytic activity toward UA oxidation in phosphate buffer solution (0.1M, pH2) to a well-defined oxidation peak at 0.65V (vs. Ag/AgCl). The polyDQV-modified carbon paste electrode (CPE/polyDQV) presents a precise linear signal-concentration relationship in the ranges of 0.3-5μM and 5 to 200μM with a detection limit (S/N = 3) of 0.02μM. The %RSD values for ten replicate measurements of 0.5 and 50μM UA were 1.8 and 3%, respectively, indicating good repeatability of analytical signals. Appropriate recovery values (in the range 96 to 103%) and good selectivity for UA over common coexisting species (such as ascorbic acid and dopamine) exhibit that CPE/polyDQV is a promising novel platform for sensing UA in human blood serum and urine samples. Graphical abstract.

A Novel Electrochemical Sensor Based on Au-Dy2(WO4)3 Nanocomposites for Simultaneous Determination of Uric Acid and Nitrite

Au nanoparticle-decorated Dy2(WO4)3 nanocomposites were prepared by reduction of HAuCl4 on the surface of Dy2(WO4)3 nanobelts which were synthesized by hydrothermal method. The formation of nanocomposites was confirmed by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and UV-vis absorption spectroscopy. Au-Dy2(WO4)3 based electrochemical sensor was fabricated by spreading Au-Dy2(WO4)3 aqueous solution on the surface of glassy carbon electrode (GCE) and investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The prepared sensor exhibited excellent electrocatalytic activity, stability, reproducibility and selectivity with well-separated oxidation peaks toward the electrooxidation of uric acid (UA) and nitrite (NO2−). Electrochemical determination of these two biomolecules in their mixture solution showed linear responses in the ranges of 0.04–1.0 mmol/L with a detection limit of 15 μmol/L for UA, and 0.01–1.0 mmol/L with a detection limit of 3.5 μmol/L for NO2−. The sensor can be applied in determination of UA and NO2− in human urine samples.

Amperometric determination of uric acid, creatinine and cholesterol on planar electrodes modified by gold particles in the flow-injection system

A method of amperometric determination of uric acid ( UA ), creatinine ( Cr ) and cholesterol ( CHO ) on planar carbon electrodes ( PE ) modified by gold particles in a flow-injection system has been developed. PE with immobilized gold particles ( Au-PE ) is catalytically active with respect to UA, Cr and CHO. A multiple current increase at modifier oxidation potentials and an oxidation potential decrease of the organic compound as compared to the unmodified electrode during their electrooxidation on Au-PE was observed. The effect of the electrochemical and hydrodynamic parameters of the flow-injection system on the analytical signal was estimated for each compound. The working conditions (applied potential and flow rate) for the maximum analytical signal registration at the modified electrode for the studied biologically active compounds ( BAC ) were selected. With the joint presence of the considered BAC, the dependence graphs of the current on the analyte concentration in logarithmic units were linear in the range from 5x10 -9 to 5x10 -3 mol/l for UA, from 5x10 -7 to 5x 0 -3 mol/l for Cr and from 5x10 -8 to 5x10 -3 mol/l for CHO. Using the two-detector flow system and double planar electrodes ( DPE ) modified with gold particles ( Au-DPE ) allowed the simultaneous determination of the considered BAC. The proposed method was used to determine UA, Cr and CHO in the urine. Keywords: electrooxidation of uric acid, creatinine and cholesterol, modified planar electrode, gold particles, amperometric determination, flow-injection analysis DOI: http://dx.doi.org/10.15826/analitika.2019.23.3.005 (Russian) L. G. Shaidarova, I.A. Chelnokova, I.A. Abzalova, A.V. Gedmina, G.K. Budnikov Kazan (Volga region) Federal University (KFU), ul. Kremlyovskaya, 18, Kazan, 420008, Russia Federation

ELECTROCHEMICAL INVESTIGATION OF DA AND UA ON CARBOXYLATED GRAPHENE OXIDE/LANTHANUM ELECTRODES WITH SUNDRY CONTENT OF CTAB

Glassy carbon electrodes (GCE) were modified by carboxylated graphene oxide/lanthanum with various concentrations of hexadecyl trimethyl ammonium bromide (CTAB), and the treated electrodes, called CTAB/GO-COOLa/GCE, were prepared for the detection of uric acid (UA) and dopamine (DA) by using the differential pulse voltammetry (DPV) and the cyclic voltammetry (CV). The results show that the modified electrode’s electrocatalytic activity could be affected by several factors in the examination, they are the pH value of the system, the main content of CTAB, various concentrations and rates of scan. With a combination of carboxylated graphene oxide/lanthanum and CTAB, the resulted CTAB/GO-COOLa/GCE sensors showed preeminent selectivity and obvious catalytic property toward the electro-oxidation of UA and DA. In optimized conditions, the response of the CTAB/GO-COOLa/GCE electrode for DA was linear in the region of 0.03–500.0[Formula: see text][Formula: see text]M with detection limits of 0.036[Formula: see text][Formula: see text]M [Formula: see text]. Two linear response ranges for the determination UA were obtained from ranges of 1 to 200[Formula: see text][Formula: see text]M and 200 to 1300[Formula: see text][Formula: see text]M with a detection limit of 0.42[Formula: see text][Formula: see text]M [Formula: see text]. Moreover, the refined electrode was used in the inspection of DA and UA in real samples of serum and urine successfully, displaying its potential application of real samples involved in electroanalysis.

Poly (Bromophenol Blue)-Gold Nanoparticle Composite: An Efficient Electrochemical Sensing Platform for Uric Acid

A simple voltammetric sensor has been developed for direct determination of important biomarker uric acid (UA) based on poly bromophenol blue - gold nanoparticles composite modified glassy carbon electrode. Scanning electron microscopy, atomic force microscopy and various electrochemical techniques were used for characterization of modified electrode surface. The electro-oxidation of UA in 0.1 M NaOH was excellently catalyzed by modified electrode. The anodic peak corresponding to the oxidation of UA was observed at a potential of −105 mV by Square wave voltammetry (SWV). The oxidation peak current was increased linearly on increasing the concentration of UA in the range 1.0 × 10−3 to 2.0 × 10−5 M (R2 = 0.994) with a limit of detection 2.2 × 10−6 M. The proposed method was effectively applied to determine Uric acid in artificial blood serum and urine samples. The developed sensor would be a potential alternative tool for UA determination in biological samples.

Amperometric detection of hydroxypurines at an electrode modified with a composite based on mixed-valence ruthenium and cobalt oxides in flow injection analysis

A composite material based on mixed-valence ruthenium and cobalt oxides, electrodeposited on the surface of a screen printed electrode, exhibits high catalytic activity in the electrooxidation of uric acid, xanthine, and hypoxanthine. Catalysis manifests itself as a decrease in the substrate oxidation overvoltage and an increase in current at the potential of modifier oxidation. A method is proposed for the simultaneous amperometric detection of two-component systems uric acid–xanthine, xanthine–hypoxanthine, and uric acid–hypoxanthine using a screen printed electrode with two working electrodes modified by this composite. The dependence of the analytical signal on the concentration of analytes is linear in the range 5 × 10–8 to 5 × 10–3 M for uric acid and xanthine and from 5 × 10–7 to 5 × 10–3 M for hypoxanthine.

Flow-injection and sequential injection determination of hydroxypurines on an electrode modified with mixed-valence ruthenium and iridium oxides

Mixed-valence ruthenium (RuOx) and iridium (IrOx) oxides and composites on their basis (RuOx-IrOx or IrOx-RuOx) electrodeposited onto the surface of a glassy carbon electrode exhibit a catalytic activity in the electrooxidation of uric acid, xanthine, and hypoxanthine. The transition from metal oxides to composites of two mixed-valence metal oxides leads to an increase in the catalytic effect of the oxidation of hydroxypurines. The IrOx-RuOx composite demonstrated the highest catalytic activity. Procedures for the amperometric detection of hydroxypurines on this composite electrode under the conditions of flow-injection analysis (FIA) and sequential injection analysis are proposed. A linear dependence of an analytical signal on the analyte concentration is observed in the range 1 × 10−6 to 5 × 10−3 M for uric acid and xanthine and 5 × 10−7 to 5 × 10−3 M for hypoxanthine under FIA conditions and from 5 × 10−7 to 5 × 10−3 M for uric acid and xanthine and 5 × 10−9 to 5 × 10−3 M for hypoxanthine in sequential injection analysis. Under FIA conditions, the sensitivity, rapidity, and performance of the analysis increase compared to the stationary conditions. The advantages of sequential injection analysis over FIA include a lower consumption of the supporting electrolyte; the absence of pumps and connections; and an increase in sensitivity, reproducibility, and rapidity.

Carbon nanotube-ionic liquid nanocomposite modified carbon-ceramic electrode for determination of dopamine in real samples

Abstract Room temperature 1-butyl-3-methylimidazolium tetraflouroborate ([BMIM][BF4]) ionic liquid was employed for dispersion of multi walled carbon nanotubes (MWCNTs) and the formation of nanocomposite on the surface of a carbon-ceramic electrode. The surface of the modified electrode was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The modified electrode exhibited excellent electrochemical activity to oxidation of dopamine (DA); whereas electro oxidation of ascorbic acid (AA) was not seen and electro oxidation of uric acid (UA) appeared at a more positive potential than DA. The multi walled carbon nanotube-ionic liquid nanocomposite modified carbon-ceramic electrode was used for the selective determination of DA in the presence of high levels of AA and UA using differential pulse voltammetry. The calibration curve for DA was linear in the range of 3.00 to 130 µM with the detection limit (S/N=3) of 0.87 µM. The present electrode was successfully applied to the determination of DA in some commercial pharmaceutical samples and human blood serum.

Simultaneous determination of dopamine, ascorbic acid, and uric acid using helical carbon nanotubes modified electrode

Helical carbon nanotubes (HCNTs) as a novel carbon material have been prepared and the catalytic activities of HCNTs-modified glassy carbon electrode (GCE) towards the electrooxidation of uric acid (UA), ascorbic acid (AA), and dopamine (DA) have been investigated. Comparing with the bare GCE, the HCNTs modified GCE (HCNTs/GCE) has higher catalytic activities towards the oxidation of AA, DA, and UA. Moreover, the peak separations between AA and DA, and DA and UA at the HCNTs/GCE are 102 and 245 mV, respectively. Thus the simultaneous determination of AA, DA, and UA was carried out successfully. In the co-existence system of AA, DA, and UA, the linear response range for AA, DA, and UA are 7.5–180 μM, 2.5–105 μM and 6.7–65 μM, respectively and the detection limits ( S/ N = 3) are 0.92 μM, 0.8 μM and 1.5 μM, respectively.

Hollow nitrogen-doped carbon microspheres pyrolyzed from self-polymerized dopamine and its application in simultaneous electrochemical determination of uric acid, ascorbic acid and dopamine

Hollow nitrogen-doped carbon microspheres (HNCMS) as a novel carbon material have been prepared and the catalytic activities of HNCMS-modified glassy carbon (GC) electrode towards the electro-oxidation of uric acid (UA), ascorbic acid (AA) and dopamine (DA) have also been investigated. Comparing with the bare GC and carbon nanotubes (CNTs) modified GC (CNTs/GC) electrodes, the HNCMS modified GC (HNCMS/GC) electrode has higher catalytic activities towards the oxidation of UA, AA and DA. Moreover, the peak separations between AA and DA, and DA and UA at the HNCMS/GC electrode are up to 212 and 136mV, respectively, which are superior to those at the CNTs/GC electrode (168 and 114mV). Thus the simultaneous determination of UA, AA and DA was carried out successfully. In the co-existence system of UA, AA and DA, the linear response range for UA, AA and DA are 5–30μM, 100–1000μM and 3–75μM, respectively and the detection limits (S/N=3) are 0.04μM, 0.91μM and 0.02μM, respectively. Meanwhile, the HNCMS/GC electrode can be applied to measure uric acid in human urine, and may be useful for measuring abnormally high concentration of AA or DA. The attractive features of HNCMS provide potential applications in the simultaneous determination of UA, AA and DA.

In situ fabricated iodine-adlayer assisted selective electrooxidation of uric acid in alkaline media

This work presents the electrooxidation of uric acid (UA) at an iodine-adlayer-modified gold, Au (I|Au (poly)) electrode in 0.1 M NaOH solution using cyclic voltammetric, amperometric and open-circuit potential measurement techniques. A tremendous enhancement of the electrode activity towards the electrooxidation of UA was achieved by virtue of the simple modification of the Au (poly) electrode surface with a neutral iodine-adlayer, fabricated in situ through the spontaneous oxidative chemisorption of iodide present in the sample solution. The cyclic voltammetric peak current increases remarkably for the oxidation of UA and the peak potential shifts by 365 mV to the negative direction of potential compared to the bare Au (poly) electrode. Oxidation of ascorbic acid (AA) at the I|Au (poly) electrode takes place at the same potential as that at the bare electrode, but the peak current intensity is almost twice at the bare Au (poly) electrode as compared to the modified one. In the mixture of the AA and UA, the cyclic voltammetric signals corresponding to the oxidations of AA and UA were resolved by 340 mV. The electrode response in the mixture was highly reproducible because of the inhibition of adsorption of oxidation products and UA.

Electrochemical synthesis of polyaniline nano-networks on p-aminobenzene sulfonic acid functionalized glassy carbon electrode : Its use for the simultaneous determination of ascorbic acid and uric acid

A composite film of polyaniline (PAN) nano-networks/ p-aminobenzene sulfonic acid (ABSA) modified glassy carbon electrode (GCE) has been fabricated via an electrochemical oxidation procedure and applied to the electro-catalytic oxidation of uric acid (UA) and ascorbic acid (AA). The ABSA monolayer at GCE surface has been characterized by X-ray photo-electron spectroscopy (XPS) and electrochemical techniques. Atomic force microscopy (AFM), field emission scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), UV–visible absorption spectra (UV–vis) and cyclic voltammetry (CV) have been used to investigate the PAN-ABSA composite film, which demonstrates the formation of the composite film and the maintenance of the electroactivity of PAN in neutral and even in alkaline media. Due to its different catalytic effects towards the electro-oxidation of UA and AA, the modified GCE can resolve the overlapped voltammetric response of UA and AA into two well-defined voltammetric peaks with both CV and differential pulse voltammetry (DPV), which can be used for the selective and simultaneous determination of these species in a mixture. The catalytic peak currents are linearly dependent on the concentrations of UA and AA in the range of 50–250 and 35–175 μmol l −1 with correlation coefficients of 0.997 and 0.998, respectively. The detection limits for UA and AA are 12 and 7.5 μmol l −1, respectively. Besides the good stability and reproducibility of PAN-ABSA/GCE due to the covalent attachment of ABSA at GCE surface, the modified electrode also exhibits good sensitivity and selectivity.

Electrochemical tagging of urate: developing new redox probes.

The electro-oxidation of uric acid in the presence of nucleophilic species is shown to produce conjugates that can aid our understanding of antioxidant interactions and also provide opportunities for advancing electroanalytical detection strategies involving purine species.

Investigation of the electrocatalytic behavior of single-wall carbon nanotube films on an Au electrode

The voltammetric behavior of uric acid (UA) was studied with an Au electrode modified with single-wall carbon nanotubes (SWNTs). In 0.1 M HAc–NaAc buffer solution (pH 5.0), the SWNT-modified electrode shows high electrocatalytic activity toward UA oxidation. The electro-oxidation of UA is an irreversible diffusion-controlled process with a diffusion coefficient ( D) of 8.85×10 −6 cm 2 s −1. The peak current increases linearly with the concentration of UA in the range of 4.0×10 −6–7.0×10 −4 M. The detection limit is 1.0×10 −6 M. The SWNT was characterized with scanning electron microscopy (SEM). Furthermore, the SWNT-modified electrode has favorable electrocatalytic activity toward dopamine and norepinephrine. This SWNT-modified electrode can also separate the electrochemical responses of uric acid, norepinephrine and ascorbic acid.

Electrochemical oxidation and kinetics of the decay of UV-absorbing intermediate of uric acid oxidation at pyrolytic graphite electrodes

The electrochemical oxidation of uric acid has been studied in 0.50 M NaCl and phosphate buffers of ionic strength 0.05 to 0.5 M. The kinetics of the decay of UV-absorbing intermediate generated during electrooxidation of uric acid (7,9-dihydro-1H-purine-2,6,8-(3H)-trione) has also been studied. On the basis of pseudo first order rate constants observed in different media, it has been concluded that the diimine species formed from the 2e, 2H+ oxidation of uric acid is attacked by water to give diol, which then decomposes in a series of reactions to give allantoin as the major product at pH 7.2. The possibility of attack by phosphate on diimine has been ruled out.

On-line electrochemistry/thermospray/tandem mass spectrometry as a new approach to the study of redox reactions: the oxidation of uric acid.

The electrochemical oxidation pathway of uric acid was determined by on-line electrochemistry/thermospray/tandem mass spectrometry. Intermediates and products formed as a result of electrooxidation were monitored as the electrode potential was varied. Several reaction intermediates have been identified and characterized by tandem mass spectrometry. The tandem mass spectrometric results provide convincing evidence that the primary intermediate produced during the electrooxidation of uric acid has a quinonoid diimine structure. The results indicate that once formed via electrooxidation, the primary intermediate can follow three distinct reaction pathways to produce the identified final products. The final electrochemical oxidation products observed in these studies were urea, CO2, alloxan, alloxan monohydrate, allantoin, 5-hydroxyhydantoin-5-carboxamide, and parabanic acid. The solution reactions that follow the initial electron transfer at the electrode are affected by the vaporizer tip temperature of the thermospray probe. In particular, it was found that at different tip temperatures either hydrolysis or ammonolysis reactions of the initial electrochemical oxidation products can occur. Most importantly, the results show that the on-line combination of electrochemistry with thermospray/tandem mass spectrometry provides otherwise difficult to obtain information about redox and associated chemical reactions of biological molecules such as the structure of reaction intermediates and products, as well as providing insight into reaction pathways.

A high-performance liquid chromatographic assay of the electro-oxidation of purines : Uric Acid and the Nucleotide Drug Tubercidin-5′-Monophosphate

A high-performance liquid chromatographic assay is described for establishing the completeness of electro-oxidation of a purine nucleotide drug tubercidin-5′-monophosphate (TMP) and the sequence of product formation. The assay shows that TMP was completely oxidized after ca. 2 h of electrolysis and that the product distribution continued to change after this time. The same assay was also used to show the sequence of product formation in the electro-oxidation of uric acid. Both separations were isocratic, with a 0.02 M potassium dihydrogenphosphate (pH 4.6–5.1) mobile phase.