490-83-5Relevant articles and documents
Kinetics of oxidation of ascorbate by tetranuclear cobalt(III) complexes ('hexols') in aqueous solution
Abdur-Rashid, Kamaluddin,Dasgupta, Tara P.,Burgess, John
, p. 1393 - 1398 (1996)
The kinetics of oxidation of L-ascorbic acid (H2A) by cobalt(III) hexols, [Co{CoL4(μ-OH)2}3]6+ [L4 =(NH3)4, (en)2, or tren; en = ethane-1,2-diamine, tren = tris(2-aminoethyl)amine], was studied as a function of pH, L-ascorbic acid concentration, temperature and ionic strength, using stopped-flow and conventional spectrophotometric techniques. The rate of the reaction is first order with respect to the concentration of each reactant and increases as [H+] decreases. The kinetic data indicate involvement of the monoprotonated and deprotonated ascorbate species (HA- and A2-) in the redox process. For L4 = (NH3)4 the rate constants, k2 and k3 are 0.22 ± 0.02 and (5.51 ± 0.09) × 105 dm3 mol-1 s-1 respectively at 25°C, and the corresponding activation parameters are ΔH?2 = 103 ± 7 kJ mol-1, ΔS?2 = 89 ± 22 J K-1 mol-1 and ΔH?3 = 46 ± 3 kJ mol-1 and ΔS?3 = 19 ± 11 J K-1 mol-1. The variations in rate constants and activation parameters for the series of complexes mentioned above are discussed. The Fuoss theory was applied to the redox process to estimate the ion-pair formation constant and the rate constant for the electron transfer.
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Silverblatt et al.
, p. 137,138 (1943)
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A new method for thermal analysis: Ion-attachment mass spectrometry (IAMS)
Fujii, Toshihiro
, p. 17 - 25,9 (2012)
In this study, we developed the technique of Li+ ion-attachment mass spectrometry (IAMS), a method that has shown promise in the fields of chemical analysis, plasma diagnostics, chemical process monitoring, and thermal analysis. The experimental setup is such that Li+ ions get attached to chemical species (R) by means of intermolecular association reactions to produce (R + Li)+ adduct ions, which are then transferred to a quadrupole mass spectrometer. Recently, an IAMS system became available commercially in a complete form from the Canon Anelva Corp. IAMS has several notable features. It provides only molecular ions, and it permits direct determination of unstable, intermediary, and/or reactive species. Also, it is highly sensitive because it involves ion-molecule reactions. With regard to its applications for thermal analysis, one of its greatest advantages is that it can be used to directly analyze gaseous compounds because it provides mass spectra only of the molecular ions formed by Li+ ion attachment to any chemical species introduced into the spectrometer, including free radicals. Coupled with evolved gas analysis, IAMS works well for the analysis of nonvolatile, untreated, and complex samples because the simplicity of the ion-attachment spectrum permits the analysis of mixtures electron-impact spectra of which are difficult to interpret.
Kinetics and Mechanisms of the Photo-Induced Oxidation of Ascorbic Acid by Molecular Oxygen Catalyzed by Ruthenium(II) Complexes Containing 2,2'-Bipyridine and 2,2'-Bipyrazine
Tsukahara, Keiichi,Wada, Yuuko,Kimura, Masaru
, p. 908 - 915 (1991)
Hydrogen peroxide was efficiently produced by the irradiation of visible light on aqueous acid solutions containing ascorbic acid, molecular oxygen, and ruthenium(II) complexes: (2+) (x=0-3, bpy=2,2'-bipyridine, and bpz=2,2'-bipyrazine).The formation of hydrogen peroxide and the decay of ascorbic acid were followed by polarography during continuous irradiation by visible light of the solution.The rate constants of the quenching reaction of the excited triplet state of the ruthenium(II) complexes by ascorbate and molecular oxygen obtained from the initial rate method were in good agreement with those obtained from luminescence quenching experiments.The initiation reaction in the photo-induced reaction mechanism changes from the oxidative quenching of *(2+) by molecular oxygen to the reductive quenching of *(2+), *(2+), or *(2+) by ascorbate.Such a change in the mechanism arises from a difference in the redox potentials, E0(Ru(3+)/*Ru(2+)) and E0(*Ru(2+)/Ru(+)), for each ruthenium(II) species containing bpy and bpz.The detailed mechanisms are discussed.
Kinetic study of the oxidation of ascorbic acid by aqueous copper(II) catalysed by chloride ion
Sisley, Margaret J.,Jordan, Robert B.
, p. 3883 - 3888 (1997)
Two methods of monitoring the chloride-catalysed oxidation of ascorbic acid by aqueous CuII have been developed that allow the reaction conditions to be varied more widely than previously and thereby permit a fuller elucidation of the behaviour and rate law for this system. It has been possible to study the reaction over a wide concentration range from 1.6 to 500 mM Cl- and 4 to 100 mM CuII. For the first time, it is shown that the ascorbic acid (H2asc)-CuII-chloride ion-CuI-dehydroascorbic acid (dha) system comes to equilibrium, under anaerobic conditions, with all species present and is driven towards products by chloride complexation of CuI. The results are consistent with the following reaction scheme (i = 0-2). The full rate law has been elucidated and values for various k1i, k-2i, and k2i/k-1i have been determined. (Chemical Equation Presented).
Kinetic Studies of the Oxidation of L-Ascorbic Acid by the Peroxodisulfate Ion, and of Copper(II)-catalysis
Kimura, Masaru,Kobayashi, Akiko,Boku, Keiko
, p. 2068 - 2073 (1982)
Kinetic studies of the oxidation reaction of L-ascorbic acid by the peroxodisulfate ion(S2O82-) are carried out in an aqueous solution over the pH range of 3.4-4.6 at various ionic-strengths from 0.071 to 1.07 M (1 M=1 mol dm-3) with NaClO4, and at four temperatures between 15 and 30 deg C, at an ionic-strength of 1.07 M.The variations in the rate of the oxidation with the hydrogen-ion concentrations are consistent with the reaction schemes involving two pH-related species; ascorbic acid H2A (k1=0.032 M-1 s-1 at 25 deg C, ΔH1=17 kJ mol-1, ΔS1=-220 J deg-1 mol-1) and the ascorbic anion HA- (k2=0.43 M-1 s-1 at 25 deg C, ΔH2=45 kJ mol-1, ΔS2=-102 J deg-1 mol-1).A relationship of log k2=-1.47+2.17 I1/2/(1+I1/2) is found with the ionic-strength (I) at 25 deg C.The reaction rate is greatly catalyzed by the presence of trace amounts of the copper(II) ion; the mechanisms of the copper(II)-catalyzed reaction are discussed.
Controlled synthesis of graphene-Gd(OH)3 nanocomposites and their application for detection of ascorbic acid
Ruan, Hong,Liu, Baoyong,Li, Hongguang
, p. 21242 - 21248 (2015)
In this report, graphene-gadolinium hydroxide (GR-Gd(OH)3) nanocomposites have been prepared using the hydrothermal process. The crystalline structures of GR-Gd(OH)3 have been determined by X-ray diffraction (XRD) measurements and their morphologies have been revealed by field-emission scanning electron microscopy (FE-SEM) observations. The optical properties of GR-Gd(OH)3 have been examined by UV-vis and Fourier transform infrared (FTIR) measurements which revealed mutual interactions between GR and Gd(OH)3. GR-Gd(OH)3 was used to modify the glassy carbon electrode (GCE) which was subsequently utilized for electro-oxidation of ascorbic acid (AA) by cyclic voltammetry method. It was found that the electro-catalytic behavior of GCE modified by GR-Gd(OH)3 (GCE/GR-Gd(OH)3) was superior to that of the bare GCE. The catalytic oxidation peak current showed a linear dependence on the AA concentration and a linear calibration curve was obtained in the concentration range of 0.1-2.5 mM of AA with the lowest limit of detection (LOD) of 0.06 mM. Simultaneously, the oxidation peaks of AA over GCE/GR-Gd(OH)3 shifted to lower over potential compared to that of GCE modified by Gd(OH)3 (GCE/Gd(OH)3). The results indicate that GR-Gd(OH)3 can be used as a promising electrode modifier, which offers a new promising platform for application of the rare earth compound in electrochemistry and bioelectronics. Synchronously, the controlled synthesis of GR-Gd(OH)3 opens an efficient and facile strategy to design other GR-based, rare earth-containing nanocomposites.
Effects of pre-micelles of anionic surfactant SDS on the electron transfer reaction between methylene blue and ascorbic acid
Sen, Pratik K.,Mukherjee, Piyali,Pal, Biswajit
, p. 472 - 479 (2016)
The effect of pre-micellar cluster of the anionic surfactant sodium dodecyl sulphate (SDS) on the electron transfer reaction between methylene blue (MB) and ascorbic acid (AA) in dilute acid medium has been investigated in the temperature range 298–308?K. The reaction is first order each with respect to MB as well as AA. The reaction involves two parallel paths - one uncatalyzed and the other H+-catalyzed path resulting in the rate law, kobs?=?(k0?+?k1 [H+]) [AA] [MB]. Iodide ion has been found to have a specific accelerating effect on the reaction rate. The reaction appears to take place between undissociated AA molecule and MB+/HMB2?+ cation. Anionic surfactant SDS shows an inhibiting effect on the reaction rate in the pre-micellar region, ultimately leading to a limiting value. The inhibiting effect of SDS has been explained in terms of Piszkiewicz's co-operativity model. The co-operativity index (n) value varies from 1.45 to 1.76 in the studied temperature range. The values of KS (the dissociation constant of the pre-micelle), n and surfactant concentration lead to the fact that the electrostatic binding in the pre-micelle is reasonably strong and most of the MB molecules remain in the pre-micelle cluster before the electron transfer with AA takes place. The formation of pre-micelle is exothermic in nature and thus favored at lower temperature.
Determination of vitamin C with chloramine T
Verma,Gulati
, p. 2336 - 2338 (1980)
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Potential antitumor activity of 2-O-α-D-glucopyranosyl-6-O-(2-pentylheptanoyl)-L-ascorbic acid
Miura, Kaori,Haraguchi, Misaki,Ito, Hideyuki,Tai, Akihiro
, (2018)
Intravenous administration of high-dose ascorbic acid (AA) has been reported as a treatment for cancer patients. However, cancer patients with renal failure cannot receive this therapy because high-dose AA infusion can have side effects. To solve this problem, we evaluated the antitumor activity of a lipophilic stable AA derivative, 2-O-α-D-glucopyranosyl-6-O-(2-pentylheptanoyl)-L-ascorbic acid (6-bOcta-AA-2G). Intravenous administration of 6-bOcta-AA-2G suppressed tumor growth in colon-26 tumor-bearing mice more strongly than did AA, even at 1/10 of the molar amount of AA. Experiments on the biodistribution and clearance of 6-bOcta-AA-2G and its metabolites in tumor-bearing mice showed that 6-bOcta-AA-2G was hydrolyzed to 6-O-(2-propylpentanoyl)-L-ascorbic acid (6-bOcta-AA) slowly to yield AA, and the results suggested that this characteristic metabolic pattern is responsible for making the antitumor activity of 6-bOcta-AA-2G stronger than that of AA and that the active form of 6-bOcta-AA-2G showing antitumor activity is 6-bOcta-AA. In in vitro experiments, the oxidized form of 6-bOcta-AA as well as 6-bOcta-AA showed significant cytotoxicity, while the oxidized forms of ascorbic acid showed no cytotoxicity at all, suggesting that the antitumor activity mechanism of 6-bOcta-AA-2G is different from that of AA and that the antitumor activity is due to the reduced and oxidized form of 6-bOcta-AA. The findings suggest that 6-bOcta-AA-2G is a potent candidate as an alternative drug to intravenous high-dose AA.
The fabrication of an Ni6MnO8 nanoflake-modified acupuncture needle electrode for highly sensitive ascorbic acid detection
Jia, Hongliang,Zhao, Jianwei,Qin, Lirong,Zhao, Min,Liu, Gang
, p. 26843 - 26849 (2019)
The current work describes the use of a steel acupuncture needle as an electrode substrate in order to construct an Ni6MnO8 nanoflake layer-modified microneedle sensor for highly sensitive ascorbic acid detection. For the purpose of constructing the functionalized acupuncture needle, first, a carbon film was layered on the needle surface as the seed layer. Subsequently, a straightforward hydrothermal reaction-calcination process was employed for the growth of Ni6MnO8 nanoflakes on the needle to function as a sensing interface. Electrochemical investigations illustrated the fact that the Ni6MnO8 nanoflake-altered acupuncture needle electrode manifested outstanding efficiency toward the amperometric identification of ascorbic acid. In addition, the electrode manifested elevated sensitivity of 3106 μA mM-1 cm-2, detection limit of 0.1 μM, and a broad linear range between 1.0 μM and 2.0 mM. As demonstrated by the results, the Ni6MnO8 nanoflake-modified acupuncture needle constitutes a potentially fresh platform to construct non-enzymatic ascorbic acid sensors.
Kinetic Investigation of the Reactions Connected to the System Ascorbate + O2 by Amperometric Detection of H2O2 at a Modified Platinum Electrode
Zambonin, Carlo G.,Losito, Ilario
, p. 4113 - 4119 (1997)
A Pt electrode modified by an electrochemically produced bilayer polymeric membrane [polypyrrole/poly(o-phenylenediamine)] entrapping the enzyme glucose oxidase proved able to detect (response time of few seconds) amperometrically (at +0.7 V vs Ag/AgCl) very low concentrations of hydrogen peroxide (micromolar range) in the presence of much higher amounts of ascorbate. The currents due to ascorbate, also electroactive at the given potential, were negligible under any conditions due to its almost complete rejection by the electrode-modifying membrane system. The very peculiar properties of the device setup were exploited to undertake a kinetic study of the reactions connected to the system ascorbate + 02, following the concentration of H2O2 produced in the reaction mixture at 27 °C, pH = 7. The reaction between ascorbate and H2O2 was also considered; however, different kinetic models based on the two consecutive reactions proved unable to fit the data. An investigation on the single processes by the same experimental approach was then undertaken, leading to two explanations for the inadequacy of simple kinetic models. First, the presence of metal ion traces in the reaction mixture proved to be responsible for the nonlinear dependence of the rate of both reactions on the ascorbate concentration: a mechanism involving the role of ascorbate-metal complexes as the reactants was hypothesized to explain this result. Second, the influence of the reactivity of dehydroascorbic acid, the product of ascorbate oxidation, on the kinetics was ascertained.
Determination of dehydroascorbic acid in mouse tissues and plasma by using tris(2-carboxyethyl)phosphine hydrochloride as reductant in metaphosphoric acid/ethylenediaminetetraacetic acid solution
Sato, Yasunori,Uchiki, Takayuki,Iwama, Mizuki,Kishimoto, Yuki,Takahashi, Ryoya,Ishigami, Akihito
, p. 364 - 369 (2010)
Ascorbic acid (AA) has a strong anti-oxidant function evident as its ability to scavenge superoxide radicals in vitro. Moreover, AA is an essential ingredient for post-translational proline hydroxylation of collagen molecules. Dehydroascorbic acid (DHA), the oxidized form of AA, is generated from these reactions. In this study, we describe an improved method for assessing DHA in biological samples. The use of 35mM tris(2-carboxyethyl)-phosphine hydrochloride (TCEP) as a reductant completely reduced DHA to AA after 2 h on ice in a 5% solution of metaphosphoric acid containing 1mM ethylenediaminetetraacetic acid (EDTA) at pH 1.5. This method enabled us to measure the DHA content in multiple tissues and plasma of 6-weeks-old mice. The percentages of DHA per total AA differed markedly among these tissues, i.e., from 0.8 to 19.5%. The lung, heart, spleen and plasma had the highest levels at more than 10% of DHA per total AA content, whereas the cerebrum, cerebellum, liver, kidney and small intestine had less than 5% of DHA per total AA content. This difference in DHA content may indicate an important disparity of oxidative stress levels among physiologic sites. Therefore, this improved method provides a useful standard for all DHA determinations.
Kinetic study of the oxidation of L-ascorbic acid by chromium (VI)
Perez-Benito,Arias
, p. 221 - 227 (1993)
The reaction between chromium (VI) and L-ascorbic acid has been studied by spectrophotometry in the presence of aqueous citrate buffers in the pH range 5.69-7.21. The reaction is slowed down by an increase of the ionic strength. At constant ionic strength, manganese(II) ion does not exert any appreciable inhibition effect on the reaction rate. The rate law found is r = Kpkr[Cr(VI)] [L-ascorbic acid] [H+]/(1 + Kp[H+]) where Kp is the equilibrium constant for protonation of chromate ion and kr is the rate constant for the redox reaction between the active forms of the oxidant (hydrogenchromate ion) and the reductant (L-hydrogenascorbate ion). The activation parameters associated with rate constant kr are Ea = 20.4 ± 0.9 kJ mol-1, ΔH≠ = 19 ± 0.9 kJ mol-1, and ΔS≠ = -152 ± 3 J K-1 mol-1. The reaction thermodynamic magnitudes associated with equilibrium constant Kp are ΔH0 = 16.5 ± 1.1 kJ mol-1 and ΔS0 = 167 ± 4J K-1 mol-1. A mechanism in accordance with the experimental data is proposed for the reaction.
A highly selective and simultaneous determination of ascorbic acid, uric acid and nitrite based on a novel poly-N-acetyl-l-methionine (poly-NALM) thin film
Kannan, Ayyadurai,Sivanesan, Arumugam,Kalaivani, Govindasamy,Manivel, Arumugam,Sevvel, Ranganathan
, p. 96898 - 96907 (2016)
This paper demonstrates the facile fabrication of an N-acetyl-l-methionine (NALM) polymer film on a glassy carbon electrode (GCE) by an electropolymerization technique. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical techniques such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the modified electrode. This poly-NALM/GCE not only exhibits strong electrocatalytic activity towards the oxidation of ascorbic acid (AA), uric acid (UA) and nitrite with a shift in oxidation potential towards the less positive side, but also enhances peak current responses at physiological pH (7.2) conditions. Further, the overlapped anodic voltammetric peaks of the three analytes on a bare GC electrode were well-resolved into their independent oxidation peaks at the poly-NALM/GC modified electrode with a peak separation of 160 and 590 mV for AA-UA and UA-nitrite, respectively. Under the optimal experimental conditions, the anodic peak currents of AA, UA and nitrite increased linearly within the concentration ranges 10-1000 μM, 1-600 μM and 1-500 μM with correlation coefficients of 0.990, 0.996 and 0.994, respectively. The detection limits are 0.97, 0.34 and 0.75 μM for AA, UA and nitrite ion, respectively (S/N = 3). The modified electrode was successfully utilized to determine AA, UA and nitrite ion simultaneously in real samples such as human urine and tap water samples.
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Tyson,Wiley
, p. 1936 (1944)
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MECHANISM OF NITROSATION OF ASCORBIC ACID BY NITRITE IN NEUTRAL AQUEOUS MEDIA
Myshkin, A. E.,Konyaeva, V. S.,Gumargalieva, K. Z.,Moiseev, Yu. V.
, p. 1961 - 1965 (1991)
The main issues in nitrosation of ascorbic acid by the nitrite ion in aqueous media are discussed.Possible mechanisms of the reaction in aqueous media with different acidities are analyzed on the basis of available published data.The main kinetic characterisatics of nitrosation of ascorbic acid in neutral Tris-HCL and phosphate buffers were obtained, and they are interpreted with due regard for the possible active participation of buffer components in the reaction.
Kinetics and mechanism of the oxidation of L-ascorbic acid by cis-diaqua cobalt(III) ammine complexes
Abdur-Rashid, Kamaluddin,Dasgupta, Tara P.,Burgess, John
, p. 1385 - 1391 (1996)
The kinetics of oxidation of L-ascorbic acid by cis-diaquacobalt(III) complexes, [CoL4(H2O)2]3+ (L4 = (NH3)4, (en)2 or tren; en = ethane-1,2-diamine, tren = tris(2-aminoethyl)amine] was studied as a fuction of pH, L-ascorbic acid concentration, temperature, ionic strength and methanol content of the solvent using stopped-flow and conventional spectrophotometry. The results indicated that only the ascorbate monoanion, HA-, is involved in the redox process with the cobalt(III) species. The rate constants for the [Co(tren)(H2O)2]3+ and [Co(tren)(H2O)(OH)]2+ species (k2 and k5) are 0.26 ± 0.09 and 1.25 ± 0.03 dm3 mol-1 s-1 respectively at 30°C, and the corresponding activation parameters are ΔH2? = 124 ± 9 kJ mol-1, ΔS2? = 137 ± 30 J K-1 mol-1 and ΔH5? = 82 ± 2 kJ mol-1, ΔS5? = 26 ± 6 J K-1 mol-1. The variations in the rate constants and thermodynamic parameters for the series of complexes is discussed. The Marcus cross-relationship for electron transfer has been applied to the redox process to confirm the outer-sphere mechanism and to estimate the self-exchange rate constant for the [CoL4(H2O)(OH)]2+/+ couple.
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Barr,King
, p. 303 (1956)
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Mechanistic studies on oxidation of l-ascorbic acid by an oxo-bridged diiron complex in aqueous acidic media
Bhattacharyya, Jhimli,Das, Suranjana,Mukhopadhyay, Subrata
, p. 1214 - 1220 (2007)
[Fe2(-O)(phen)4(H2O)2] 4+ (1) (Fig. 1, phen = 1,10-phenanthroline) equilibriates with [Fe2(-O)(phen)4(H2O)(OH)]3+ (2) and [Fe2(-O)(phen)4(OH)2]2+ (3) in aqueous solution in the presence of excess phen, where no phen-releasing equilibria from 1, 2 and 3 exist. 1 quantitatively oxidizes ascorbic acid (H2A) to dehydroascorbic acid (A) in the pH range 3.00-5.50 in the presence of excess phen, which buffers the reaction within 0.05 pH units and ensures complete formation of end iron product ferroin, [Fe(phen) 3]2+. The reactive species are 1, 2 and HA- and the reaction proceeds through an initial 1: 1 inner-sphere adduct formation between 1 and 2 with HA-, followed by a rate limiting outer-sphere one electron one proton (electroprotic) transfer from a second HA- to the ascorbate-unbound iron(III). The Royal Society of Chemistry 2007.
Visible light-induced oxidation of ascorbic acid and formation of hydrogen peroxide
Kurimura,Yokota,Muraki
, p. 2450 - 2453 (1981)
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Purification of crude In(OH)3 using the functionalized ionic liquid betainium bis(trifluoromethylsulfonyl)imide
Deferm, Clio,Luyten, Jan,Oosterhof, Harald,Fransaer, Jan,Binnemans, Koen
, p. 412 - 424 (2018)
The recovery of indium from a crude indium(iii) hydroxide using the ionic liquid betainium bis(trifluoromethylsulfonyl)imide, [Hbet][Tf2N], was investigated. Leaching and solvent extraction were combined in one step using the thermomorphic properties of the [Hbet][Tf2N]-H2O system. During leaching (80 °C) a homogeneous phase was formed. Upon lowering the temperature below the lower critical solution temperature (UCST), the dissolved metals distributed themselves between the two phases. The optimal leaching/extraction conditions were determined to be a leaching time of 3 hours at 80 °C in a 1:1 wt/wt [Hbet][Tf2N]-H2O mixture. Large separation factors (>100) between In(iii) and Al(iii), Ca(ii), Cd(ii), Ni(ii) and Zn(ii) were obtained implying an easy separation. Fe(iii), As(v) and Pb(ii) are co-extracted. The separation factor between indium and iron was improved to >1000 by addition of ascorbic acid to reduce Fe(iii) to Fe(ii). The stripping was done very efficiently by HCl solution. The ionic liquid was regenerated during the stripping step. By combining a prehydrolysis and hydrolysis step, indium(iii) hydroxide with a purity >99% was obtained.
VALENCE CHANGE OF COPPER IN CATALYTIC OXIDATION OF L-ASCORBIC ACID BY MOLECULAR OXYGEN
Ito, Sotaro,Yamamoto, Toshimasa,Tokushige, Yuji
, p. 1411 - 1414 (1980)
The copper(II) chloride-catalyzed oxidation of L-ascorbic acid (AA) by O2 was found to involve both the anaerobic oxidation of AA by copper(II) chloride and the reoxidation steps of copper(I) chloride by O2 in the catalytic cycle, by comparing the rate of copper(II)-catalyzed oxidation of AA by O2 (RAIIO) with those of anaerobic oxidation of AA by copper(II) (RAII) and oxidation of copper(I) by O2 (RIO).
Highly sensitive and efficient voltammetric determination of ascorbic acid in food and pharmaceutical samples from aqueous solutions based on nanostructure carbon paste electrode as a sensor
Pardakhty, Abbas,Ahmadzadeh, Saeid,Avazpour, Sanaz,Gupta, Vinod Kumar
, p. 387 - 391 (2016)
A square wave voltammetric method for the trace analysis of ascorbic acid was developed in this study. Carbon paste electrode was modified with NiO nanoparticle and 1-butyl-3-methylimidazolium tetrafluoroborate as a binder. Electro-oxidation behavior of ascorbic acid on the modified electrode was studied, which indicated that the nanostructure modified electrode could efficiently promote electrocatalytic oxidation of ascorbic acid. A fast, selective, high sensitive and simple electrochemical strategy was then developed for trace analysis of ascorbic acid using the constructed electrode. The catalytic oxidation signal exhibited a wide linear range from 0.08 to 380.0 μM toward the concentration of ascorbic acid with a sensitivity of 0.0158 μA/μM, and the limit of detection was as low as 0.04 μM. The suggested sensor was also used for quantitative determination of ascorbic acid in food and pharmaceutical samples.
Possible Formation of Dehydro-L-ascorbic Acid from 2,3-Diketo-L-gulonic Acid in an Aqueous Solution
Miyake, Noriko,Kurata, Tadao
, p. 1419 - 1421 (1998)
The reaction of 2,3-diketo-L-gulonic acid (DKG), which is one of the important intermediate products in the degradation of L-ascorbic acid (ASA) in both food and biological systems, in an aqueous solution was studied. The formation of a small amount of the γ-lactone, dehydro-L-ascorbic acid (DASA), from DKG was observed. This strongly suggests the chemical possibility of a reverse reaction in DASA hydrolysis which has been long believed to be irreversible.
High Recovery of Selenium from Kesterite-Based Photovoltaic Cells
Abás, Elisa,Asensio, Maria Pilar,Laguna, Mariano,Pinilla, Jose Luis
, (2020/06/02)
The use of photovoltaic cells is constantly increasing and, in particular, a new generation of thin-film photovoltaic (PV) cells is under development. The absorber of these new cells, kesterite (CZT(S)Se), is composed of abundant chemical elements. Nonetheless, the development of the recycling process for these elements is indispensable for circular economy. This research is focused on the recovery of selenium by thermal oxidation and subsequent reduction. Thus, recycling of selenium has been firstly studied on synthetic kesterite and then validated in a real sample of kesterite extracted from glass-based PV cells. The best results were obtained in a vertical tubular furnace at 750 °C with an input of 20 mL/min of air. The posterior reduction process of selenium oxide was achieved by ascorbic acid, a common and economic reagent. Real kesterite was extracted from PV cells by thermal treatment at 90 °C for 1 hour to remove the encapsulant and ulterior treatment with HCl for the release of kesterite absorber. Optimal conditions from synthetic kesterite were applied to a real sample, recovering more than 90 % of selenium with a purity of 99.4 %.
A novel polyoxometalate-based metal-organic nanotube framework templated by twin-Dawson clusters: Synthesis, structure and bifunctional electrocatalytic properties
Lu, Borong,Li, Shaobin,Zhang, Xiaozhou,Zhang, Deqing,Fan, Linlin,Yan, Eryun,Zhang, Yongjuan,Yu, Liang
, p. 15804 - 15810 (2019/10/19)
A novel polyoxometalate-based metal-organic framework templated by twin-Dawson clusters, [{Cu3(μ3-O)}2(trz)6Cu2(H2O)13][H1.73P2As1.73W16.27O62]·8.25H2O (1) (trz = 1,2,4-triazole), has been synthesized under hydrothermal conditions. In 1, there are two crystal distinct motifs: a 3D metal-organic nanotube framework and seven-connected Dawson clusters. It is worth mentioning that the 3D framework possesses nanotube-like channels. The twin-H1.73P2As1.73W16.27O62 clusters (abbreviated as P2(As/W)18 clusters) as templates occupy channels of the nanotube framework. To the best of our knowledge, this represents the first metal-organic nanotube framework templated by twin-Dawson clusters. The electrochemical experiments indicate that the 1-based glassy carbon electrode (1-GCE) possesses high catalytic efficiency and high stability toward reduction of inorganic bromate molecules and oxidation of the biological molecule ascorbic acid. The electrocatalytic efficiency towards the reduction of bromate in 1 M H2SO4 solution and oxidation of AA in N2 purged solution is ca. 848.4% and 896.8% (catalytic substrate: 0.5 mM), respectively. The current signal after 100 cycles exhibits almost no loss for 1-GCE.