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Estradiol (E2) is a hormone that influences various aspects of women's health. Beyond its reproductive functions, E2 impacts neurotransmitter systems such as dopamine (DA). Vertically aligned carbon nanofibers (VACNFs) have shown good sensitivity, selectivity against ascorbic acid (AA) and uric acid (UA), biocompatibility, and reduced fouling in DA sensing. In this study, we explore the use of Ti-Ni-CNF electrodes with CNFs grown for 5 min and 30 min for the direct electrochemical co-detection of E2 and DA. The longer growth time led to a 142% increase in average CNF length and a 36% larger electroactive surface area. In E2 detection, the electrodes demonstrate a wide linear range of 0.05–10 µM and sensitivity of 0.016 and 0.020 µA/µM for Ti-Ni-CNF-5 min and Ti-Ni-CNF-30 min, respectively. The sensor performance remains largely unaffected even in the presence of other steroid hormones such as progesterone and testosterone. Co-detection of equimolar E2 and DA shows promising peak separation of 0.34 ± 0.01 V and repeatability after 10 measurements. A notable improvement in the E2/DA peak current ratio, from 0.53 ± 0.07 to 0.81 ± 0.16, was achieved with the increased CNF length. Our results demonstrate the influence of adsorption sites in electrochemical detection, especially for analytes such as E2 and DA that both rely on adsorption for oxidation. While detecting small and fluctuating physiological concentrations remains a challenge, these findings can be used in choosing and fabricating electrode materials for more accurate and accessible continuous hormone measurements, including the possibility of multianalyte sensing platforms. [ABSTRACT FROM AUTHOR]

In this work, an electrochemical method for sensitive determination of creatinine has been reported based on its reaction with 2-nitrobenzaldehyde and using differential pulse voltammetry technique. A plausible mechanism of the reaction has been proposed and successful application of this method for creatinine detection in a real sample (human urine) has also been demonstrated. The mechanism is indicative of the formation of multiple electroactive species in the process. The linear range of detection being 1–25 mM, with LOD of 0.50 mM and an excellent R2 value of 0.99, was suitable enough for the detection of creatinine in human urine. Interference studies of urea, uric acid, glucose, ascorbic acid and dopamine were done and found to be within the acceptable limit. All the components except uric acid showed an interference of less than 3.2%, while uric acid showed maximum interference of 8.4%. Its robustness, high selectivity, good sensitivity, and low detection limit have projected it as a promising new tool for a point-of-care testing device. [ABSTRACT FROM AUTHOR]

Simultaneous determination of small biologically important molecules is more significant for monitoring several diseases at physiological pH. Uric acid (C5H4N4O3) and ascorbic acid (C6H8O6), for instance, were once regarded as crucial components in the physiological processes of humans since they coexist in numerous biological matrices regularly, and monitoring their concentrations simultaneously indicates diseases like gout. In the present work, the gold nanoparticles (AuNPs) were assembled on a glassy carbon electrode (GCE) using electrodeposition of Au3+ ions for the simultaneous determination of C5H4N4O3 and C6H8O6. The deposited AuNPs were characterized using UV–visible spectroscopy, XPS, XRD, and AFM. Morphological analysis depicted that the particles are spherical with a size of 32 nm, and the particles are uniformly distributed on the electrode surface. The formation of gold oxide and its reduction peaks in cyclic voltammetry revealed the effective deposition of AuNPs on the GCE surface. The catalytic activity AuNPs modified GCE was analyzed by probing the oxidation of C5H4N4O3 and C6H8O6 at physiological pH (pH 7.2). The present modified electrode greatly enhanced the oxidation peak currents, and the potential of oxidation is also shifted to less positive potential compared to bare GCE. The AuNPs/GCE was used to determine C5H4N4O3 in the presence of a 50-fold high concentration of C6H8O6. The detection of 40 nM C5H4N4O3 was achieved using amperometry and a detection limit of 1.8 × 10–9 M (Signal/Noise = 3) was observed for the determination of uric acid in the concentration range from 4 × 10–8 to 4 × 10–5 M. [ABSTRACT FROM AUTHOR]

In this paper, an ultra-sensitive glassy carbon electrode modified with β-cyclodextrin and graphene oxide (β-CD-GO/GCE) has been prepared for the detection of biomolecules [ascorbic acid (AA), dopamine (DA) and uric acid (UA)] in aqueous solution at μM level. The three biomolecules (AA, DA and UA) can be simultaneously detected by the modified electrodes, and the electrical signals corresponding to various biomolecules can be identified clearly in cyclic voltammetry and differential pulse voltammetry curves. The simultaneous detection limits of AA, DA, UA were 4.58, 1.56, 1.27 μM, respectively. This ultra-sensitivity should be attributed to the formation of host–guest complexes between β-CD and the biomolecules. Furthermore, the anti-interference experiments indicated the β-CD-GO/GCE exhibited satisfactory selective recognition performance. [ABSTRACT FROM AUTHOR]

Selectivity of dopamine (DA), uric acid (UA), and ascorbic acid (AA) is an open challenge of electrochemical sensors in the field of biosensing. In this study, two selective mechanisms for detecting DA, UA, and AA biomolecules on the pristine boron nitride nanosheets (BNNS) and functionalized BNNS with tryptophan (Trp), i.e., Trp@BNNS have been illustrated through density functional density (DFT) calculation and charge population analysis. Our findings reveal that the adsorbed biomolecules on Trp@BNNS indicate the less sensitivity factor of biomolecule separation than the functionalized biomolecules with Trp (Trp@biomolecule) adsorbed on pristine BNNS. From the calculations, strong adsorption of Trp@biomolecule on the pristine substrate corresponds to enhancing of electron charge transfer and electrical dipole moment. Our analysis is in good agreement with the previous theoretical and experimental results and suggests new pathway for electrode modification for electrochemical biosensing. [ABSTRACT FROM AUTHOR]

The integration of the enzymes on the solid electrode surfaces is an indispensable step for the construction of the bioelectrochemical electrode. In the current work, the blend nanofibers consisting of poly (vinyl alcohol) and poly(ethyleneimine) were deposited by the electrospinning method on an H2O2-sensitive modified glassy carbon electrode. Glucose oxidase was immobilized on the glutaraldehyde-activated blend nanofibers. Bioelectrochemical electrode displayed a good linear response to the glucose concentration ranges with two separate calibration curves, from 2 to 8 mmol L−1 and from 10 to 30 mmol L−1. Besides, it showed a high anti-interference performance against ascorbic and uric acids as well as long-term storage stability over 63 days. Moreover, analysis results in a diluted human serum sample showed that the prepared bioelectrochemical electrode has the ability to measure glucose in real samples. [ABSTRACT FROM AUTHOR]

A simple Co3O4 modified carbon paste electrode (CPE) was developed as an electrochemical sensor for the selective detection and quantification of dopamine (DA) via fastest synthesis and fabrication methods. The solution combustion method and bulk modification techniques were sequentially used for the preparation of the sensor. The modifier was characterized using different techniques such as PXRD, FT-IR, SEM and TG-DSC. The fabricated sensor shows a wide linear dynamic range of 80 µM-300 nM, low detection limit, excellent reproducibility and high stability. The differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques were extensively used for the electrochemical studies. The same electrode was used for detecting DA in the solution of coexisting ascorbic acid (AA) and uric acid (UA). Well resolved peaks and good current sensitivity of this electrochemical sensor extended its utility in determining DA in blood serum at physiological pH. [ABSTRACT FROM AUTHOR]

In this work, UV/Vis spectroelectrochemistry (SEC), in a thin-layer regime and parallel configuration, is selected to solve a complex mixture that contains dopamine (DA), ascorbic acid (AA) and uric acid (UA). These molecules, like many other biological compounds, are assuming a highly important place in analytical and biomedical fields due to the fundamental role that they play in human metabolism. In addition, low or high levels of these compounds are associated with diseases such as Parkinson's disease. For this reason, the quantification of these biomolecules is becoming increasingly critical. However, some drawbacks must be overcome, because the three molecules coexist in the human body, and the species are subject to mutual interference. In fact, they are all oxidized at similar potentials, and their UV/Vis absorption bands overlap, greatly complicating their quantification. For this reason, derivative SEC together with suitable chemometric tools such as PARAFAC are proposed to solve this complex matrix. This technique allows us to separate the contribution of each of these molecules present in a sample and to quantify all of them, achieving high resolution and reproducibility. Besides, detection limits at the micromolar level are achieved for DA, AA and UA in mixture solutions. This work thus demonstrates the great potential for derivative potentiodynamic SEC combined with the appropriate chemometric tools in solving complex mixtures, a field where SEC is still taking the first steps. [ABSTRACT FROM AUTHOR]

Au/CuO nanoparticles with a size range of 20–40 nm directly synthesized by solution plasma method in water have been successfully applied to the non-enzyme detection of glucose. The electrocatalytic activities of Au/CuO nanoparticles toward glucose were evaluated in an alkaline solution by cyclic voltammetry and real-time current method. Research results demonstrate that the biosensor modified by Au/CuO catalysts has a fast reaction time (< 3 s) and low detection limit (0.22 µM). There are two specific linear ranges of 0.22 µM–1 mM and 3 mM–18 mM, with the sensitivities of 172.45 µA mM−1 cm−2 and 63.66 µA mM−1 cm−2, respectively. Moreover, it also exhibited remarkable current response, good stability (87% after 50 days), superior reproducibility, and excellent selectivity in interfering species (such as D-fructose, ascorbic acid and uric acid). Therefore, the Au/CuO nanoparticles directly synthesized by solution plasma method can be implemented to the enzyme-free detection of glucose. [ABSTRACT FROM AUTHOR]

Uncontrolled oxidative stress, reported in Salmonella and HIV infections, colorectal cancer or severe acute malnutrition, has been associated with anaerobic gut microbiome alteration, impaired butyrate production, mucosal immunity dysregulation and disruption of host-bacterial mutualism. However, the role of major antioxidant molecules in the human body, such as glutathione, ascorbic acid and uric acid, has been neglected in this context. Here, we performed an in vitro metabolomics study of the 3 most odorous anaerobic microbes isolated from the human gut in our laboratory (Clostridium sporogenes, Clostridium subterminale and Romboutsia lituseburensis) when grown in anaerobiosis or in aerobiosis with these 3 antioxidant molecules via gas and liquid chromatography-mass spectrometry (GC/MS and LC/MS). There was no growth or volatile organic compound production in aerobic cultures without the 3 antioxidant molecules. In anaerobiosis, the major metabolic products of the bacteria were thiols, alcohols and short-chain fatty acid esters. The production of alkanes, cycloheptatriene and, paradoxically, increased butyrate production, was observed in the cultures grown in aerobiosis with the 3 antioxidant molecules. The qualitative shift suggests specific molecular mechanisms that remain to be elucidated. The increased production of butyrate, but also isobutyrate and isovalerate in vitro suggests that these 3 antioxidant molecules contributed to the maintenance and active resilience of host-bacterial mutualism against mucosal oxygen and uncontrolled oxidative stress in vivo. [ABSTRACT FROM AUTHOR]

A glassy carbon electrode has been modified by electrochemical polymerization of dianix yellow along with multi-walled carbon nanotubes (MWCNTs) and utilized for the selective determination of dopamine (DA), ascorbic acid (AA) and uric acid (UA). Atomic force microscopy and scanning electron microscopy images were obtained to compare the surface morphology and topography of the bare and modified electrodes. Also, the electrochemical activities of DA, AA, and UA on the bare and modified electrodes were evaluated with the use of cyclic, linear sweep and differential pulse voltammetry (DPV). Large peak separation, good sensitivity, and stability allow to apply the poly-dianix yellow/MWCNTs modified electrode for the determination of DA individually and in the presence of AA and UA. The DPV data showed the linearity of DA, AA, and UA peak currents in the concentrations ranges of 7–2500 nM, 5–110 µM, and 0.100–7.500 µM with the detection limits of 6.1, 99 and 8.9 nM, respectively. The proposed electrode was applied for the quantification of dopamine in human blood serum samples. [ABSTRACT FROM AUTHOR]

Abstract: Active electrocatalytic electrode designs are needed for the sensitive and selective detection of a single or multi-active biomolecule among biological components. We report the design of hierarchical NiO catalyst (HNC) for one-step monitoring of bioactive molecules such as ascorbic acid (AA), dopamine (DA), and uric acid (UA). The novel mesostructured geometries, active surface sites, and multi-diffused spaces for easy electron movement through gaps provide highly active electrocatalytic electrode designing surface. Controlled HNC architecture along electrode-design surface domains having double-head branches spread out along both sides of the dipole-like rod may lead to the vital electron transfer and fast response signaling of multi-bioactive molecules in one-shot triggering individually or simultaneously. Electrochemical analyses showed evidence that the proposed electrode design can detect each component up to 0.02 µM. Sensitive detection up to 1.127, 0.02, and 0.978 µM and wide-range responses of 25-800, 2-60, and 10-000 µM for AA, DA, and UA, respectively, were observed. The simultaneous monitoring and selective signaling of AA, DA, and UA in real urine samples in one step under different potentials were realized. Thus, the HNC-modified electrode can monitor and evaluate the coexistence of biomolecules simultaneously in multi-components.Graphical Abstract: The electrochemical oxidation of AA, DA, and UA at the HNC-modified electrode and the corresponding DPV peaks with losing of 2e−/2H+. [ABSTRACT FROM AUTHOR]

Objectives: To compare the effects of lotus root and cucumber on antioxidant function in aged subjects. Design: Pilot comparative study. Setting: Research setting with vegetable intervention. Participants: Healthy aged subjects over the age of sixty. Intervention: 30-day supplementation of lotus root or cucumber powder. Measurements: Plasma value of ferric reducing antioxidant power assay, activity of antioxidant enzymes, contents of some antioxidants, oxidation products, hemolysis, blood mononuclear cell DNA damage and urinary excretion of 8-hydroxy-2'-deoxyguanosine were measured before and after the intervention. Results: Plasma glutathione peroxidase activity, contents of vitamin C, total phenolics were significantly increased, while plasma uric acid content significantly decreased in both groups at the end of the intervention. Meanwhile, hemolysis was significantly reduced in both groups and DNA injury rate of blood mononuclear cells in lotus root group and the ratio of comet tail length to total length in cucumber group were also declined significantly post-intervention. However, plasma value of ferric reducing antioxidant power assay, contents of reduced glutathione, vitamin E, malondialdehyde, oxidized low density lipoprotein, carbonyls and activity of superoxide dismutase and catalase were not changed significantly in both group after the intervention. Conclusion: These results suggest that lotus root and cucumber are not remarkably different in improving antioxidant function in aged subjects, though they are significantly different in antioxidant capacity in vitro. The benefits observed in this study may come from the additive or synergistic combinations of antioxidants contained in vegetables. [ABSTRACT FROM AUTHOR]

This paper describes the construction, evaluation, and application of an electrochemical sensor for the determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). Satisfactory results were achieved for the simultaneous determination of DA and UA, it was verified that it is possible to detect AA in the presence of DA, but high concentrations of AA interfere in detection of DA. The sensor was constructed using the layer-by-layer (LbL) technique with the modification of the surface of indium tin oxide coated glass (ITO) substrate with nanostructured films comprising a 3- n-propylpyridinium silsesquioxane polymer (SiPyCl) and nickel(II) tetrasulfophthalocyanine (NiTsPc). Using the square wave voltammetry technique (SWV), the LbL modified electrodes produced at different pHs (pH 2 and 8) were used to determine DA in the presence UA, and the electrochemical responses of the electrodes were compared. It was observed that the electrodes with the highest concentration of monomeric species showed the highest current intensity and the lowest peak potential for the DA and UA analytes in analysis of DA and UA, individually and simultaneously, with peak potential separation of 460 mV versus Ag/AgCl. Applying SWV, a linear dynamic range of 10-99 μmol L and 100-900 μmol L with detection limit of 16.8 μmol L and 58.3 μmol L was obtained for DA and UA, respectively. The method has good selectivity and sensitivity, and it was successfully applied to the simultaneous determination of DA and UA in spiked human urine sample. [ABSTRACT FROM AUTHOR]

A selective determination of levodopa (LD) in the presence of ascorbic acid (AA) and uric acid (UA) has been investigated at a glassy carbon electrode modified with reduced graphene oxide (rGO). The graphene oxide was synthesized chemically by Hummers method and characterized by energy-filtered transmission electron microscopy (EF-TEM). The reduced graphene oxide modified glassy carbon electrode (rGO/GCE) showed excellent electrochemical performance in the simultaneous electrochemical detection of LD, AA, and UA due to the unique properties of graphene, such as large surface area, facile electronic transport and high electrocatalytic activity. The redox characteristics of rGO/GCE were investigated with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Well-resolved oxidation peak potentials, corresponding to the oxidation of AA, LD, and UA, were observed from their mixture solution at 0.098, 0.285, and 0.423 V, respectively. The rGO/GCE showed that LD can be detected without the interference of AA and UA. Under the optimized conditions, the oxidation peak current of LD is linear with the concentration of LD from 2.0 to 100 μM with the detection limit of 1.13 μM (S/N = 3). The present electrode system was also successfully applied to direct determination of LD in commercially available tablets and urine samples. [ABSTRACT FROM AUTHOR]

This paper describes a rapid and reliable method for dopamine (DA), ascorbic acid (AA), and uric acid (UA) determination in human urine using a cathodically pretreated poly(1-aminoanthraquinone) (PAAQ)-modified electrode. By applying a simple cathodic pretreatment to the PAAQ electrode well-defined voltammetric peaks for AA, DA, and UA were obtained. The pretreated PAAQ showed good selectivity, sensitivity, and repeatability for measuring AA, DA, and UA with detection limits of 2.50 × 10, 3.05 × 10, and 1.15 × 10 M, respectively. The practical applicability of the modified electrode is illustrated by selective measurements of AA and UA in human urine without any preliminary treatment. Recovery values between 94.8 and 102 % for AA and between 77.8 and 100 % for UA were obtained with a relative standard deviation of 2.74 and 2.98 %, respectively. [ABSTRACT FROM AUTHOR]

This study was aimed to examine the effect of vitamin C/E intake alone or combined with resistance training on antioxidant/pro-oxidant status, muscle strength and body composition in an elderly population. Fifty-seven men and women with a mean age of 65.6 ± 3.8 years were recruited and randomized in a double-blind fashion into four groups: control-placebo; resistance training (RT); vitamins C/E supplementation (AS); AS+RT. Oxidative stress status and metabolic and lipid profiles were determined at baseline and after six months. Fat-free mass and fat mass measured by DXA were similar at baseline for all groups. At six month, there was a significant difference among the groups as a function of vitamin E supplementation. Moreover, although there was no effect on pro-oxidative parameters, a significant effect on body composition was noted, but no difference was noted on strength gain. The combination of RT+AS had a positive effect on the plasma antioxidant profile but not on the pro-oxidant status. [ABSTRACT FROM AUTHOR]

In this paper, the silver doped poly (L-glutamic acid) modified glassy carbon electrode (PLG-Ag/GCE) was fabricated through an electrochemical immobilization. The modified electrode was used for simultaneous determination of uric acid ( UA) and ascorbic acid ( AA) in 0.1 M phosphate buffer solutions (PBS). The cyclic voltammetric signals of UA and AA were well separated with a potential difference of 396 mV in pH 3.0 phosphate buffer solution. The linear calibration curves were obtained in the concentration range 5.00 × 10-1.00 × 10 M for UA and 8.00 × 10-5.00 × 10 M for AA with the detection limits of 3 × 10 M and 4 × 10 M, respectively. The relative standard deviations were 1.3 and 1.0% for the determinations of UA and AA for 20 continuous measurements. The signal was highly stable and reproducible. This method was successfully applied to the determination of UA in human urine samples. [ABSTRACT FROM AUTHOR]

The electrocatalytic behavior of uric acid has been investigated with a glassy carbon electrode modified with p-aminobenzene sulfonic acid through electrochemical polymerization. This resulting electrode shows an excellent electrocatalytic response to uric acid and ascorbic acid, with a peak-to-peak separation of 0.267 V in a 0.1 mol L−1 phosphate buffer solution (PBS) at pH 7.0. These results indicate that the proposed electrode can eliminate the serious interference of ascorbic acid, which coexists with uric acid in body fluids. Differential pulse voltammetry (DPV) was used for detecting uric acid with selectivity and sensitivity. The anodic peak current of uric acid was proportional to its concentration in the range of 1.2 × 10−7–8.0 × 10−4 mol L−1, with a detection limit of 4.0 × 10−8 mol L−1. The proposed method has been applied with satisfactory results to the determination of uric acid in human urine without any pretreatment. [ABSTRACT FROM AUTHOR]

The aim of the present analysis was to study the influence of the sample concentration on the measured antioxidant capacity, since such investigations are scarce but necessary to ensure the reproducibility of the results. Pure substances (ascorbic acid, gallic acid, Trolox®, uric acid) and food extracts (strawberry nectar, tomato extract, white tea) were analysed using seven common antioxidant capacity assays (three versions of Trolox equivalent antioxidant capacity, TEAC; ferric reducing antioxidant power, FRAP; photochemiluminescence, PCL; oxygen radical absorbance capacity, ORAC and total phenolics assay). For all applied pure substances and in most of the assays effects of the sample concentration on the measured antioxidant capacity were observed. Since it remains speculative how sample concentration does affect the measured antioxidant capacity exactly, it is strongly recommended to use at least three sample concentrations for analysis to detect and to discuss concentration-dependent effects. [ABSTRACT FROM AUTHOR]

A sensitive and selective electrochemical method for the determination of norepinephrine using a poly (Evans Blue) film-modified glassy carbon electrode was developed. The polymer film-modified electrode shows excellent electrocatalytic activity toward the oxidation of norepinephrine ( NE) in phosphate buffer solution (pH 5.0). The linear range of 5.0 × 10−7–1.8 × 10−5 M and detection limit of 3.5 × 10−8 M were observed for the determination of NE in pH 5.0 phosphate buffer solutions. The interference studies showed that the modified electrode had excellent selectivity for the determination of NE in the presence of large excess of ascorbic acid ( AA) and uric acid ( UA). The differences of the oxidation peak potentials for NE-AA and NE-UA were about 175 and 172 mV, respectively. The resolution is large enough to determine AA, NE and UA individually. This work provides a simple and easy approach to selective detection of NE in the presence of AA and UA in physiological samples. [ABSTRACT FROM AUTHOR]

Palladium (Pd) incorporated poly (3,4-ethylenedioxythiophene) (PEDOT) films were synthesized through an electrochemical route and characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The electrochemical study showed catalytic oxidation of dopamine (DA) with optimum loading of Pd. DA and uric acid (UA) were detected using differential pulse voltammetry (DPV). In the presence of ascorbic acid (AA), DA-AA showed peak potential separation of 0.19 V while 0.32 V between UA-AA on Pd-incorporated PEDOT. These peak separations are large enough for sensing DA and UA in the presence of AA. DA and UA exhibited linear calibration plots and the minimum detection limits are 0.5 and 7 µM respectively. On Pd-PEDOT, the reversibility of DA oxidation was found to increase compared to bare glassy carbon electrode (GCE) and PEDOT modified GCE. Fouling effects were also found to be minimal making Pd-PEDOT composite suitable for electroanalysis. [ABSTRACT FROM AUTHOR]

Binuclear copper complex (2-[bis(2-aminoethyl)amino]ethanol, 4,4′-bipyridine bridged dicopper(II) complex) was grafted onto the surface of a glassy carbon electrode (GCE) using the cyclic voltammetric method in a phosphate buffer solution (PBS). The modified electrode resulted in efficient electrocatalytic activity for anodic oxidation of uric acid (UA) and ascorbic acid (AA) via a substantial decrease in anodic over-potentials for both compounds. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using this modified electrode result in two well-resolved anodic waves for the oxidation of UA and AA in mixed solution, making possible the simultaneous determination of both compounds. Linear analytical curves were obtained in the ranges 5.0–300.0 μM and 5.0–160.0 μM for UA and AA concentrations through DPV methods, respectively. The detection limits were 2.0 μM of UA and AA. This electrode was used for UA and AA determinations in urine samples with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel method for rapid separation and determination of ascorbic acid and uric acid has been developed with a polycation-modified poly(dimethylsiloxane) (PDMS) microchip under a negative-separation electric field. Just by flushing the microchip with aqueous solutions of the polycations, poly(allylamine) hydrochloride, poly(diallyldimethylammonium chloride) or chitosan could be stably coated on the PDMS microchannel surface, which resulted in a reversed electroosmotic flow and thus the rapid and efficient separation of the two substrates. Factors influencing the separation, including polycation category, buffer solution, detection potential and separation voltage, were investigated and optimized. The cheapness, rapid analysis speed and the successful analysis of human urine make this microsystem attractive for application in clinics. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Self-assembled monolayers (SAMS) of chemisorbed thioglycollate on a gold electrode surface have been used as a base interface for the electrostatic adsorption of ferrocenium ion. Electrochemical impedance spectra (EIS) and cyclic voltammetry (CV) were used to evaluate the electrochemical properties of the supramolecular film. The bare gold electrode failed to distinguish the oxidation peaks of ascorbic acid (AA) and uric acid (UA) in phosphate buffer solution (PBS, pH 7.0), while the ferricinium–thioglycollate modified electrode could separate them efficiently. In differiential pulse voltammetric measurements, the prepared gold electrode could separate AA and UA signals, allowing the simultaneous determination of AA and UA. Under optimal conditions and within the linear range of 1.0 × 10−6 to 5.0 × 10−4 M, the detection limits of AA and UA achieved were 2.0 × 10−7 and 1.0 × 10−7 M, respectively. The applicability of the prepared electrode was demonstrated by measuring AA and UA in human urine without any pretreatment. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The biomass-derived activated carbons (ACs) have been prepared with high surface areas up to 793 m2 g−1 is by ZnCl2 activation at three different temperatures, viz. AC700, AC800, and AC900. The AC samples were characterized by a variety of analytical and spectroscopy techniques. The as-synthesized ACs were adopted for the simultaneous electrochemical detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). For comparison, reduced graphene oxide (RGO) was employed for the proposed sensor. The high surface area, modulated pore size and the presence of oxygen surface functional groups like heteroatoms (83.427% C, 1.085% N, 0.383% S, and 0.861% H) in the biomass-derived AC is found to be responsible for the excellent catalytic activities of biomolecules. Fascinatingly, the facile sensor further used to detect biomolecules levels in the snail hemolymph and human blood serum. Notably, the obtained analytical parameters for the biomolecules detection over the AC modified GCE, outperforming several carbon-based modified electrodes in literatures. [ABSTRACT FROM AUTHOR]