Selective Determination Of Ascorbic Acid Research Articles

Fe Doping Enhances the Peroxidase-Like Activity of CuO for Ascorbic Acid Sensing

Although significant advances have been witnessed in the application of nanozymes in recent years, exploring new strategies to enhance the enzyme-like activity of nanozymes is of urgent importance. Herein, we investigate the feasibility of accelerating the peroxidase-like reaction rate of CuO nanostructures through Fe doping. The coprecipitation method was used to synthesize Fe-doped CuO (Fe-CuO) nanozymes, and the results indicate that the diversified valence of Fe benefits the redox reaction driven by CuO-based nanozymes. With the improved peroxidase-like activity, the Fe-CuO nanozyme enables the significant chromogenic oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB), facilitating the construction of a visual sensing platform for the sensitive and selective determination of ascorbic acid. Under optimal conditions, the absorbance at 652 nm decreases linearly with the concentration of ascorbic acid in the range of 5–50 μM, with a limit of detection as low as 4.66 μM. This work exemplifies the activity enhancement for peroxidase-mimicking nanozymes with a metal-doping strategy and provides a broad prospect for the design of more high-performance nanozymes for biosensing applications.

Redox-Based Colorimetric Sensor for the Selective Determination of Ascorbic Acid in Fixed-Dose Combination Tablets.

Ascorbic acid (ASC; vitamin C) is a weak chromophore, so its presence cannot be determined directly by spectrophotometry. This work aims to develop and validate a simple and ecofriendly analytical method for the determination of ASC concentration based on the reaction of ASC with the metal complex, ferric salicylate. The visible absorbance of ferric salicylate was found to be inversely proportional to the concentration of ASC. The possible mechanism of the reaction between ASC and ferric salicylate was investigated: ferric salicylate was found to be reduced by ASC under the applied experimental conditions. Different parameters that may affect the reaction were also investigated: ferric salicylate concentration, pH, ionic strength, and the time of reaction. The optimum concentration of ferric salicylate was found to be 1000 µM and the optimum pH was 5.5. The developed method was validated according to International Conference on Harmonization (ICH) guidelines. The linearity range of the developed method was 5-70 µg/mL and the correlation coefficient was 0.9994. The limits of detection and quantitation were 0.38 µg/mL and 1.16 µg/mL, respectively. The method was successfully applied to the determination of ASC concentration in commercial Ruta-C60® tablets. The mean recovery ± standard deviation was found to be 101.10 ± 0.70%. The results were statistically compared to those obtained by a reported HPLC method. Good agreement was observed. The developed method is simple, fast, cost-effective, and suitable for routine pharmaceutical analysis of ASC. The developed method is more sensitive than the other spectrophotometric methods reported for determination of ASC.

Design of Electrochemically Reduced Graphene Oxide/Titanium Disulfide Nanocomposite Sensor for Selective Determination of Ascorbic Acid

Design of Electrochemically Reduced Graphene Oxide/Titanium Disulfide Nanocomposite Sensor for Selective Determination of Ascorbic Acid

MoSx-Co₃O₄ Nanocomposite for Selective Determination of Ascorbic Acid.

Designing a nanocomposite with sensitive and selective determination of ascorbic acid is challenging task. It is possible through the exploitation of attractive features of nanoscience and nanotechnology for the synthesis of nanostructured materials. Herein, we report the decoration of nanoparticle of MoSx on the surface of Co₃O₄ nanowires by hydrothermal method. The MoSx nanoparticles shared the large surface on the Co₃O₄ nanowires, thus it supported in the development enzyme free ascorbic acid sensor. Non-enzymatic sensor based on MoSx-Co₃O₄ composite was found very selective for the determination of ascorbic acid (AA) in phosphate buffer solution of pH 7.4. The MoSx-Co₃O₄ nanocomposite was used to modify the glassy carbon electrode to measure AA from variety of practical samples. The MoSx-Co₃O₄ nanocomposite was used to modify the glassy carbon electrode and it has shown the attractive analytical features such as a low working potential +0.3 V, linear range of concentration from 100-7000 μM, low limit of detection 14 μM, and low limit of quantification (LOQ) of 42 μM. The developed sensor is highly selective and stable. Importantly, it was applied successfully for the practical applications such as detection of AA from grapefruit, tomato and lemon juice. The excellent electrochemical properties of fabricated MoSx-Co₃O₄ nanocomposite can be attributed to the increasing electro active surface area of MoSx. The presented nanocomposite is earth abundant, environment friendly and inexpensive and it holds promising features for the selective and sensitive determination of AA from practical applications. The nanocomposite can be capitalized into the wide range of biomedical applications.

A highly sensitive biosensor based on methacrylated graphene oxide-grafted polyaniline for ascorbic acid determination

Abstract Functionalized graphene-based nanocomposites have opened new windows to address some challenges for increasing the sensitivity, accuracy and functionality of biosensors. Polyaniline (PANI) is one of the most potentially promising and technologically important conducting polymers, which brings together the electrical features of metals with intriguing properties of plastics including facile processing and controllable chemical and physical properties. PANI/graphene nanocomposites have attracted intense interest in various fields due to unique physicochemical properties including high conductivity, facile preparation and intriguing redox behavior. In this article, a functionalized graphene-grafted nanostructured PANI nanocomposite was applied for determining the ascorbic acid (AA) level. A significant current response was observed after treating the electrode surface with methacrylated graphene oxide (MeGO)/PANI nanocomposite. The amperometric responses showed a robust linear range of 8–5,000 µM and detection limit of 2 µM (N = 5). Excellent sensor selectivity was demonstrated in the presence of electroactive components interfering species, commonly found in real serum samples. This sensor is a promising candidate for rapid and selective determination of AA.

A novel voltammetric platform composed of poly(aminopyrazine), ZrO2 and CNTs for a rapid, sensitive and selective determination of ascorbic acid in pharmaceuticals and food samples

An electrochemical platform based on a composite of poly(aminopyrazine) (PAP), zirconium oxide nanoparticles (ZrO2NPs) and carbon nanotubes (CNTs) was prepared. A GCE was first modified with CNTs and ZrO2NPs via a drop-casting technique. Then, the ZrO2NPs/CNTs/GCE system was immersed into an aqueous solution of 1 mM aminopyrazine (AP) containing 10 mM LiClO4 in a potential range of −1.5 V–1.5 V for 20 cycles to carry out the polymerization step. The composite layer was characterized by energy dispersive X-ray (EDX), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The proposed voltammetric platform (PAP/ZrO2NPs/CNTs on GCE) was applied for the electrooxidation of ascorbic acid (AA). Compared with ZrO2NPs/CNTs/GCE, CNTs/GCE and GCE, the proposed novel system (PAP/ZrO2NPs/CNTs/GCE) presented an effective catalytic activity for the oxidation of AA with a large enhancement in the current response. The procedure has also enabled a large peak to peak separation between AA and tryptophan (TRP). A linear dynamic current response was obtained for the concentrations of AA in the range of 1.0 × 10−6 - 2.95 × 10−4 M with a detection limit of 3.5 × 10−7 M. The quantification of AA in pharmaceuticals and mixed fruit juices has successfully been performed by PAP/ZrO2NPs/CNTs/GCE.

A metal-organic frameworks@ carbon nanotubes based electrochemical sensor for highly sensitive and selective determination of ascorbic acid

A conductive electrochemical sensor for ascorbic acid was prepared by in-situ growing metal-organic frameworks (ZIF-65) on the surface of carboxylated carbon nanotubes. This nanohybrid was dropped onto glassy carbon electrodes to fabricate a modified ZIF-65@ CNTs electrode. Owing to the introduction of carboxylated carbon nanotubes, the conductivity of the sensor was enhanced with resistance decreased by half. Due to the porous crystal structures, good water-stability and oxidizing nitro groups of ZIF-65, this sensor exhibited high sensory performances to ascorbic acid with the detection limit of 1.03 μM. Excellent selectivity, anti-interference and reproducibility enabled it as a promising candidate in biomolecular sensing applications.

Facile Synthesis of Perylenetetracarboxylic Acid Modified Bismuth@Carbon Nanostructures and Its Enhanced Sensitivity for Selective Electrochemical Determination of Three Biomolecules

In this work, we present a facile, green synthetic strategy for the preparation of bismuth@carbon nanostructures (Bi@C) using glucose as carbon source via a one-pot template-free hydrothermal approach. Inspiringly, Bi@C exhibits good conductivity of organic carbon, which is very important for electrode construction. Further, to obtain more active -COOH groups and better monodispersity, Bi@C was decorated with 3,4,9,10-perylenetetracarboxylic acid (PTCA). The interesting Bi@C-PTCA nanostructures serve as a sensing platform and show well-separated oxidation peaks and enhanced peak currents for selective determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Under the optimized experimental condition, the linear responses for simultaneous detection of AA, DA and UA are 1.0–119 μM, 0.2–87.2 μM and 0.1–119.1 μM, and the detection limits are 0.27 μM, 0.06 μM and 0.03 μM (S/N = 3), respectively. Importantly, the fabricated electrochemical sensor exhibits long-term sensing stability, behaves as a good anti-interference response, and has promising applications for the determination of multi-analytes in human urine and serum samples.

Determination of Ascorbic Acid by a Gold–Zinc Oxide Nanoparticle-Modified Glassy Carbon Electrode

ABSTRACTA novel electrochemical sensing platform was developed based on flower-like gold–zinc oxide core–shell nanoparticles and a graphene nanocomposite-modified glassy carbon electrode. The gold–zinc oxide core–shell nanoflowers were synthesized by seed growth and characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and ultraviolet-visible absorption spectroscopy. The modified electrode provided good electrocatalytic properties, rapid response, high stability, and favorable reproducibility for determination of ascorbic acid. The performance of the sensor included a linear dynamic range from 1.0 × 10−7 to 6.0 × 10−4 M, a limit of detection of 3.9 × 10−8 M, and a sensitivity of 24.12 µA/mM. The nanocomposite also provided excellent selectivity and lower potential for the oxidation of ascorbic acid. The sensor was used for the determination of ascorbic acid in tablets with satisfactory results. This device provides rapid, simple, and selective determination of ascorbic acid.

A new class of electropolymerized conducting film from the pyrimidine family for the simultaneous determination of ascorbic acid and dopamine

We report the electropolymerization of 4-amino-6-hydroxy-2-mercaptopyrimidine on a glassy carbon electrode and its application for simultaneous as well as the selective determination of ascorbic acid and dopamine at pH 4.

Hydrothermal synthesis of Fe2O3/graphene nanocomposite for selective determination of ascorbic acid in the presence of uric acid

In this study, we had demonstrated a hydrothermal method to prepare Fe2O3/graphene (RG) nanocomposite for the determination of ascorbic acid (AA) in the presence of uric acid (UA). The synthesized materials were characterized by scanning electron microscopy (SEM), X-ray diffraction measurements (XRD), transmission electron microscopy (TEM) and inductively coupled plasma atomic emission spectrometry (ICP-AES). As a sensor, the Fe2O3/RG nanocomposite modified electrode exhibited synergistic effects which not only improved the electrochemical catalytic oxidation of AA, but also resolved the overlapping anodic peaks of AA and UA. And the results showed that Fe2O3/RG could be used for the determination of AA in the presence of low concentration of UA. Using the modified electrode with different concentrations of AA, the linear response range for the determination of AA in the presence UA was 0.57–3.97mM (R=0.9994). The detection limit (S/N=3) was found to be 0.543μM for the determination of AA. The results suggested that the Fe2O3/RG nanocomposite had the advantages of simplicity, high sensitivity and good selectivity for determination of AA.

Synthesis of Au/graphene oxide composites for selective and sensitive electrochemical detection of ascorbic acid.

In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM−1 cm−2 to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application.

Highly selective electrochemical sensor for ascorbic acid based on a novel hybrid graphene-copper phthalocyanine-polyaniline nanocomposites

In this work, we designed a novel electrochemical sensing platform based on graphene (Gr)/copper(II) phthalocyanine-tetrasulfonic acid tetrasodium salt (CuPc)/polyaniline(PANI) nanocomposites. The prepared composites were used to modify screen printed electrodes (SPE) for selective determination of ascorbic acid (AA) in presence of dopamine (DA) and uric acid (UA). Copper phthalocyanine was immobilized on graphene sheets by π-π interaction by electrolytical exfoliation and resulting CuPc/graphene was embedded in a PANI matrix to prevent leakage of Gr/CuPc from electrodes. The Gr/CuPc/PANI nanocomposites were characterized by scanning electron microscopy (SEM), UV-vis spectroscopy, cyclic voltammetry (CV) and amperometry. The prepared modified electrode presents good electrocatalytic properties, fast response time, high stability and reproducibility. The performance of the sensor exhibited a linear range from 5×10−7 to 1.2×10−5M with low a limit of detection of 6.3×10−8M (S/N=3) and the sensitivity of the sensor was found to be 24.46μAmM−1. Moreover, the nanocomposites show excellent selectivity and lower potential for the oxidation of ascorbic acid. The novel sensor successfully applied to determination of AA in real samples with satisfactory results. This can open up new opportunities for fast, simple and selective detection of AA and provide a promising platform for sensor or biosensor designs for AA detection.

Direct In Situ Determination of Ascorbic Acid in Fruits by Screen‐Printed Carbon Electrodes Modified with Nylon‐6 Nanofibers

AbstractA simple sensing unit based on a disposable screen printed carbon electrode coated by an electrospun nylon‐6 nanofibrous membrane was developed for in situ selective determination of ascorbic acid (AA) in different types of fruits. The membrane, prepared by electrospinning, represents a selective barrier to possible interferents, such as phenolic compounds, allowing an improved selectivity towards AA. No sample preparation and/or dilution is necessary since the new device is applied directly “pricking” the fruit with the electrode. A good correlation was obtained between the amperometric in situ method and a reference chromatographic methodology (HPLC‐UV) when applied to various fruit samples.

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.

Flow injection fluorometric determination of ascorbic acid using perylenebisimide-linked nitroxide

A simple and sensitive flow injection fluorometric method for the determination of ascorbic acid is described. Perylenebisimide-linked nitroxide (PBILN) is used as a fluorescent reagent, which permits the selective determination of ascorbic acid. The fluorescence of the perylenebisimide moiety in PBILN is quenched by the nitroxide moiety, which is linked to the perylenebisimide. When a stream of a solution of ascorbic acid is merged with a stream of PBILN, the ascorbic acid reacts with the nitroxide moiety of PBILN to form hydroxylamine, and the fluorescence properties of the perylenebisimide moiety are recovered. As a result, a peak-shaped fluorescence signal is produced, which can be observed by a fluorescence detector located downstream. Under optimized conditions, a good linear relationship between the concentration of ascorbic acid and peak height in the concentration range from 0.5 to 10μmolL−1 was found and the detection limit (S/N=3) was 0.28μmolL−1. The relative standard deviation for the determination of 4.0μmolL−1 ascorbic acid samples was 1.0% (n=5). The proposed method was applied to the determination of ascorbic acid in several soft drink beverages and the analytical results were in good agreement with those obtained using a conventional method.

Selective determination of ascorbic acid with a novel hybrid material based 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and the Dawson type ion [P2Mo18O62]6− immobilized on glassy carbon

In this study, we synthesized a new hybrid material using well-Dawson K6[P2Mo18O62]·nH2O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). CHN elemental analysis showed that one mole of [P2Mo18O62]6− reacts with 6 moles of [BMIM]+ to form [BMIM]6P2Mo18O62. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid material compared to the parent Dawson POM. The new hybrid material [BMIM]6P2Mo18O62 was immobilized on glassy carbon (GC) electrode and the modified electrode was investigated by cyclic voltammetry and amperometry. Compared to the electrochemical behavior of dissolved [P2Mo18O62]6−, a slight shift in the redox peaks towards negative potentials is observed for the immobilized [BMIM]6P2Mo18O62. The relationship between the peak currents of the deposited [BMIM]6P2Mo18O62 film and scan rate is shown to be linear, which demonstrates a surface-confined electron transfer processes. [BMIM]6P2Mo18O62 modified electrode showed high sensitivities towards pH and shown to be active even at neutral pH. [BMIM]6P2Mo18O62 modified GC electrode was subjected to cyclic voltammetry and amperometry in the presence of ascorbic acid (AA) and found to exhibit a remarkable catalytic activity towards the oxidation of AA. The catalytic oxidation peak of AA at [BMIM]6P2Mo18O62 modified GC electrode occurs at low potential of ∼0V vs Ag/AgCl at neutral pH and shifts to more positive potentials when pH decreases. Comparison between [BMIM]6P2Mo18O62 and [P2Mo18O62]6− modified GC films towards the oxidation of AA suggests that the significant decrease in the overpotentials recorded with [BMIM]6P2Mo18O62 film is related to the presence of ionic liquid cation in the hybrid material, which probably plays the role of the redox mediator. The resulting AA sensor [BMIM]6P2Mo18O62/GC has a significant sensitivity of ∼63nA/μM AA, fast response time (<9s), low detection limit (<0.1μM), high selectivity towards endogenous interferences such as uric acid, acetaminophen and dopamine, a linear range from 0.1μM to at least 22mM AA and was stable for at least 2weeks. In addition, such AA sensors can operate in a pH range from 0 to at least 7.

Aqueous Synthesis of CdTe/CdSe Core/Shell Quantum Dots as pH-Sensitive Fluorescence Probe for the Determination of Ascorbic Acid

By controlling the reflux time and the quantity of the shell materials, different sizes of thioglycollic acid (TGA) modified CdTe/CdSe core/shell quantum dots were synthesized in aqueous solution. This type of QDs was used for sensitive and selective determination of ascorbic acid in commercial tablets. Under optimal conditions, a good linearity was observed between the relative fluorescence (FL) intensity and the concentration of ascorbic acid in the range of 4.0 to 64.0 μg/mL with a correlation coefficient of 0.9968. The limit of detection was 2.4 μg/mL. This method was applied to the determination of the ascorbic acid in Vitamin C tablets and Vitamin C Yinqiao pills, and satisfactory results were obtained.

Compact Cell for the Selective Determination of Ascorbic Acid

Compact Cell for the Selective Determination of Ascorbic Acid

Highly selective determination of ascorbic acid, dopamine, and uric acid by differential pulse voltammetry using poly(sulfonazo III) modified glassy carbon electrode

A highly selective electrochemical method was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) using sulfonazo III film-modified on glassy carbon electrode. The modified electrode showed excellent electrocatalytic activity toward the oxidation of AA, DA, and UA. The calibration curves were obtained with 0.5–1300.0 μmol L −1 AA, 0.05–470.0 μmol L −1 DA, and 0.2–100.0 μmol L −1 UA. Detection limits of 0.17 μmol L −1 AA, 0.03 μmol L −1 DA, and 0.11 μmol L −1 UA were obtained. The influence of various substances on the selectivity of the sensor was studied. The results confirm the high selectivity, good sensitivity, and stability of the modified electrode. Satisfactory results were achieved for the determination of DA, AA, and UA with dopamine injection solution, vitamin C tablets, and human urine samples.