Selective Detection Of Ascorbic Acid Research Articles

Amperometric ascorbic acid biosensor based on carbon nanoplatelets derived from ground cherry husks

In this work, a novel amperometric biosensor based on carbon nanoplatelets derived from ground cherry (Physalis peruviana) husks (GCHs-CNPTs) is reported for the sensitive and selective detection of ascorbic acid (AA). The structure of the nanoplatelets, the oxygen-containing groups and edge-plane-like defective sites (EPDSs) on the GCHs-CNPTs were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The presence of GCHs-CNPTs with a high density of EPDSs effectively enhances the electron transfer between AA and the glassy carbon electrode (GCE), and thus induces a substantial decrease in the overvoltage for AA oxidation compared with both a bare GCE and a GCE modified with carbon nanotubes (CNTs/GCE). In particular, an amperometric biosensor based on GCHs-CNPTs exhibited a wider linear range (0.01–3.57mM), higher sensitivity (208.63μAmM−1cm−2), a lower detection limit (1.09μM, S/N=3) and better resistance to fouling for AA determination compared to a CNTs/GCE. The great potential of the GCHs-CNPTs/GCE for practical and reliable AA analysis was demonstrated by the successful determination of AA in samples taken from a medical injection dose and a soft drink.

Graphene Quantum Dots Functionalized with 4-Amino-2, 2, 6, 6-Tetramethylpiperidine-N-Oxide as Fluorescence "Turn-ON" Nanosensors.

In this study, we report on the fabrication of simple and rapid graphene quantum dots (GQDs)-based fluorescence "turn-ON" nanoprobes for sensitive and selective detection of ascorbic acid (AA). Pristine GQDs and S and N co-doped-GQDs (SN-GQDs) were functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4-amino-TEMPO, a nitroxide free radical). The nitroxide free radicals efficiently quenched the fluorescence of the GQDs and upon interaction of the nanoconjugates with ascorbic acid, the quenched fluorescence was restored. The linear ranges recorded were 0.5-5.7μM and 0.1-5.5μM for GQDs-4-amino-TEMPO and SN-GQDs-4amino-TEMPO nanoprobes, respectively. Limits of detection were found to be 60nM and 84nM for SN-GQDS-4-amino-TEMPO and GQDs-4-amino-TEMPO for AA detection, respectively. This novel fluorescence "turn-ON" technique showed to be highly rapid and selective towards AA detection.

Highly Sensitive and Selective Fluorescent Probe for Ascorbic Acid with a Broad Detection Range through Dual-Quenching and Bimodal Action of Nitronyl-Nitroxide

A novel nitronyl-nitroxide derivative for highly sensitive and selective detection of ascorbic acid (AA) is reported. The probe showed 260-fold fluorescence turn-on and diminished electron spin resonance (ESR) signal upon AA addition. The probe could detect AA over a broad concentration range from 1 μM to 2 mM and excellent selectivity over various antioxidants and acids through a combination of fluorescence and ESR responses, which originated from the dual-reactiveness of dual-quenching group nitronyl-nitroxide. We successfully demonstrated practical application potential of the probe by preparing nanoparticles and sensor papers and determining AA concentration in real samples including vitamin drinks and orange juices.

Piperazine functionalized mesoporous silica for selective and sensitive detection of ascorbic acid

Ordered mesoporous silica SBA-15 functionalized with piperazine (SBA/Pip) was synthesized via grafting method. Incorporation of piperazine inside the mesopores without affecting the stability of the ordered mesoporous silica could be viewed from different characterization techniques such as Powder X-ray diffraction, N2 sorption studies, Fourier-Transform Infrared spectroscopy, Scanning Electron microscopy, Transmission Electron Microscopy. The SBA/Pip nanocomposite was employed as an electrochemical sensor to detect the presence of ascorbic acid ranging from millimolar to nanomolar range via differential pulse voltammetry (DPV) in the potential window of −1.5 to +1.5 V wherein the scan rate was maintained at 4 mV/s. Further SBA/Pip displayed selective detection of ascorbic acid in packed and fresh orange juice without any interference from other acids like citric acid commonly present in packed juice.

Fe3+-functionalized carbon quantum dots: A facile preparation strategy and detection for ascorbic acid in rat brain microdialysates

This study reports an Fe3+-functionalized carbon quantum dots (Fe3+-functionalized CQDs) for the highly sensitive and selective detection of ascorbic acid (AA) in rat brain microdialysates based on the specific redox reaction between iron(III) ions and AA. The carbon quantum dots (CQDs) were synthesized by one-step pyrolysis of a small organic molecules i.e. tris(hydroxymethyl)aminomethane (Tris). Fe3+ can tightly chelate to the surface of CQDs by the hydroxyl group to form Fe3+-functionalized CQDs while the fluorescence of CQDs can be effectively quenched by Fe3+ via Fluorescence resonance energy transfer (FRET). The fluorescence of the Fe3+-functionalized CQDs can be sensitively turned on by AA to give an “on–off–on” fluorescence response through the oxidation–reduction between Fe3+ and AA since the produced Fe2+ has much lower chelating ability to CQDs and the fluorescence of CQDs can be restored. This Fe3+-functionalized CQDs based nanoprobe shows high selective and sensitive response in the concentration of AA ranging from 0.1μM to 50μM with the detection limit as lower as 9.1nM, which is lower than other assays. Finally, the proposed fluorescent probe was successfully applied to direct analysis of AA in biological fluids, i.e. rat brain microdialysates, and may pave a new route to the design of effective carbon quantum dots-based fluorescence probes for other bioassay.

A sensitive and selective chemosensor for ascorbic acid based on a fluorescent nitroxide switch

Ascorbic acid (AsA), also known as vitamin C, is a vital small-molecule antioxidant with multiple functions in vivo. It’s the major natural antioxidant found in plants and is also an essential component of human nutrition. AsA plays a key role in many diseases-related biological metabolism. Therefore, sensitive and selective detection of AsA is greatly important in pharmaceutical, clinical and food industry. Here a sensitive and selective sensor for ascorbic acid detection based on the recovered fluorescence of NAPS-NO (N-propyl-triethoxysilane-4-(4-ylamino-1-oxy-2,2,6,6-tetramethylpiperdine)- naphthalimide) probe is described. The fluorescence of the naphthalimide moiety of NAPS-NO is inhibited by the nitroxide group, which is covalently linked to the fluorophore. Then, ascorbic acid reacts rapidly with the nitroxide moiety of NAPS-NO to form hydroxylamine, and the fluorescence properties of the naphthalimide moiety are recovered and the ESR signal decayed. Over a wide range from 80nM to 50μM, a good linear relationship between the fluorescence intensity and the concentration of ascorbic acid was found and the detection limit was estimated to be as low as 20nM. To confirm the practical usefulness of the fluorophore–nitroxide probe, we demonstrated the use of NAPS-NO for the measurement of AsA in human blood serum and also successfully determined the concentration of AsA in HEK 293 cell lysate. Results from confocal laser scanning microscopy experiments demonstrated that this chemosensor is cell permeable and can be used as a fluorescent probe for monitoring ascorbic acid in living cells.

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.

Disposable Electrochemical Ascorbic Acid Sensor Based on Molecularly Imprinted Poly(o-phenylenediamine)-Modified Dual Channel Screen-Printed Electrode for Orange Juice Analysis

An electrochemical biomimetic sensor was developed for fast and selective detection of ascorbic acid (AA) in orange juice samples via electropolymerizing o-phenylenediamine on the surface of a dual channel screen-printed carbon electrode (SPCE), which could achieve two repetitive measurements by using the same sample drop and improve test efficiency. The square wave voltammograms and scanning electron microscopy images indicated that the many imprinted cavities had formed in the AA-imprinted poly(o-phenylenediamine) film, which acted as a selective recognition element to determine AA by means of the matched size, shape, and orientation of the functional groups between the imprinted cavities and AA molecules. The response current of the imprinted sensor was linearly related to the concentration of AA in both lower concentration regions (0.45–13.52 μM) and higher concentration regions (13.52–409.10 μM), respectively. The detection limit was 0.11 μM based on the signal to noise ratio of 3. The sensor was applied to determine AA in commercial orange juice, and the result was in good agreement with that obtained by 2,6-dichlorophenol indophenol titration method. The fabrication of the sensor was simple and timesaving (<35 min for modifying two work electrodes). Together with portability and disposability of the AA-MIP/SPCE, the proposed sensor had widely potential applications in field test and analysis.

Electrochemical sensor based on carbon-supported NiCoO2 nanoparticles for selective detection of ascorbic acid

An electrochemical sensor for selective detection of ascorbic acid (AA) in the presence of dopamine (DA) and uric acid (UA) was fabricated by modifying the glassy carbon electrode (GCE) with carbon-supported NiCoO2 (NiCoO2/C) nanoparticles. The electrochemical impedance spectroscopic (EIS) studies reveal the little charge transfer resistance for the modified electrode. The electrocatalytic activity of the modified electrode for the oxidation of AA was investigated. The current sensitivity of AA was enhanced to about five times upon modification. The voltammetric response of AA was well resolved from the responses of DA and UA, and the oxidation potential of AA was negatively shifted to −0.20V. The biosensor tolerated a wide linear concentration range for AA, from 1.0×10−5M to 2.63×10−3M (R2=0.9929), with a detection limit of 0.5μM (S/N=3). Our results demonstrate that the NiCoO2/C nanomaterials has excellent AA sensing capability, including a fast response time, high reproducibility and stability, with great promise in the quantification of AA in real samples. That makes it a unique electrochemical sensor for the detection of AA which is free from the interference of DA, UA and other interferents.

Hydroquinone modified chitosan/carbon film electrode for the selective detection of ascorbic acid

A redox active polymer, hydroquinone modified chitosan (Q-chitosan) was synthesized and characterized by IR and 1H NMR spectroscopy. The nanocomposite of Q-chitosan with carbon was prepared and used to construct a stable conductive film on the electrode surface. The SEM studies confirms that the Q-chitosan/C composite covers the electrode surface with polymer embedded 50nm size carbon particles. The formal redox potential, E0 of the Q-chitosan/C composite modified electrode is evaluated to be 0.09V vs. Ag/AgCl at pH 7 and the composite electrode shows an excellent electrocatalytic activity toward the ascorbic acid (AA) at 0.0V vs. Ag/AgCl. It is more negative potential than the similar AA biosensors and the lower potential oxidation of AA enabled the selective detection of AA over major interferences such as dopamine and uric acid. Using amperometric method, the linear range for ascorbic acid is estimated to be 10μM to 5mM with the detection limit of 3μM and the sensitivity is 0.076μAμM−1cm−2.

“Turn on” electron-transfer-based selective detection of ascorbic acid via copper complexes immobilized on glass

"Turn-on" optical detection of parts-per-million (ppm) levels of ascorbic acid (AA) in water has been determined using a redox-active monolayer on glass.

Gold Nanoparticles Modified Titania Nanotube Arrays for Amperometric Determination of Ascorbic Acid

Development and use of highly ordered, vertically aligned TiO2 nanotube arrays modified with gold nanoparticles for the selective detection of ascorbic acid (AA) in the presence of uric acid and glucose are reported here. Gold nanoparticles were electrodeposited on the Nanotube arrays by CV. The sensor was characterized using SEM, EDS, CV, and EIS. It showed very good performance with a sensitivity of 46.8 μA mM−1 cm−2, response time below 2 seconds and linearity in the range of 1 μM to 5 mM with a detection limit of 0.1 μM and was tested for the AA concentration in pharmaceutical preparations.

Ultrathin Pd nanowire as a highly active electrode material for sensitive and selective detection of ascorbic acid

Nanomaterial modified electrode is useful for catalytic, analytical and biotechnological applications. Herein, a simple and sensitive method for the electrocatalytic detection of ascorbic acid (AA) using ultrathin Pd nanowire (NW) modified glassy carbon electrode is presented. Electrochemical data reveal that Pd NWs can effectively enhance the electron transfer between AA and electrode, and thus reduce the overpotential of AA oxidation. Particularly, the current–time curve shows that the catalytic oxidation current is linearly dependent on AA concentration in the range of 25 μM–0.9 mM with a correlation coefficient 0.9998, and a detection limit of 0.2 μM (S/N = 3) is obtained with an excellent reproducibility. What is more, the present Pd NWs-based electrochemical sensing platform can successfully be used as enhanced element for the detection of AA in the practical samples such as human serum and vitamin C beverage with satisfactory results.

Chemical Redox Modulation of the Surface Chemistry of CdTe Quantum Dots for Probing Ascorbic Acid in Biological Fluids

Most of the fluorescence resonance energy transfer (FRET)-based sensors employing quantum dots (QDs) usually use organic fluorophores and gold nanoparticles as the quenchers. However, complex processes for the modification/immobilization of the QDs are always necessary, as the generation of FRET requires strict distance between the donor and acceptor. Herein, a simple chemical redox strategy for modulating the surface chemistry of the QDs to develop a QD-based turn-on fluorescent probe is reported. The principle of the strategy is demonstrated by employing CdTe QDs with KMnO(4) as the quencher and ascorbic acid as the target analyte. The fluorescence of CdTe QDs is quenched with a blue-shift upon addition of KMnO(4) due to the oxidation of the Te atoms on the surface of the QDs. The quenched fluorescence of the QDs is then recovered upon addition of ascorbic acid due to the reduction of CdTeO(3)/TeO(2) on the surface of the QDs to CdTe. The recovered fluorescence of the QDs increases linearly with the concentration of ascorbic acid from 0.3 to 10 microM. Thus, a novel QD-based turn-on fluorescent probe with a detection limit as low as 74 nM is developed for the sensitive and selective detection of ascorbic acid in biological fluids. The present approach avoids the complex modification/immobilization of the QDs involved in FRET-based sensors, and opens a simple pathway to developing cost-effective, sensitive, and selective QD-based fluorescence turn-on sensors/probes for biologically significant antioxidants.

Electrocatalytic oxidation of ascorbic acid at a 2,2′-(1,8-octanediylbisnitriloethylidine)-bis-hydroquinone modified carbon paste electrode

Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical behavior of ascorbic acid at a carbon paste electrode modified with 2,2′-(1,8-octanediylbisnitriloethylidine)-bis-hydroquinone (1,8-OBNEBHQ). The modified carbon paste electrode showed high electrocatalytic activity toward ascorbic acid; the current was enhanced significantly relative to the situation prevailing when an unmodified carbon paste electrode was used. The electrocatalytic process was highly dependent on the pH of the supporting electrolyte. The apparent charge transfer rate constant, ks, and transfer coefficient, α, for electron transfer between 1,8-OBNEBHQ and carbon paste electrode were calculated as 20.2 ± 0.5 s−1 and 0.47, respectively. Using differential pulse voltammetry, the calibration curves for AA were obtained over the range of 5–30 and 40–1,500 μM, respectively. The detection limit (kσ, k = 2) was 0.6 μM. With good selectivity and sensitivity, the present method provides a simple method for selective detection of ascorbic acid in biological samples.

Electrochemical selective determination of ascorbic acid at redox active polymer modified electrode derived from direct blue 71

A simple selective method for determination of ascorbic acid using polymerized direct blue 71 (DB71) is described. Anodic polymerization of the azo dye DB71 on glassy carbon (GC) electrode in 0.1 M H 2SO 4 acidic medium was found to yield thin and stable polymeric films. The poly(DB71) films were electroactive in wide pH range (1–13). A pair of symmetrical redox peaks at a formal redox potential, E ′0 = −0.02 V vs. Ag/AgCl (pH 7.0) was observed with a Nernstian slope −0.058 V, is attributed to a 1:1 proton + electron involving polymer redox reactions at the modified electrode. Scanning electron microscope (SEM), atomic force microscope (AFM) and electrochemical impedance spectroscopy (EIS) measurements were used for surface studies of polymer modified electrode. Poly(DB71) modified GC electrode showed excellent electrocatalytic activity towards ascorbic acid in neutral buffer solution. Using amperometric method, linear range (1 × 10 −6–2 × 10 −3 M), dynamic range (1 × 10 −6–0.01 M) and detection limit (1 × 10 −6 M, S/N = 3) were estimated for measurement of ascorbic acid in pH 7.0 buffer solution. Major interferences such as dopamine and uric acid are tested at this modified electrode and found that selective detection of ascorbic acid can be achieved. This new method successfully applied for determination of ascorbic acid in commercial tablets with satisfactory results.