جستجوی مقالات مرتبط با کلیدواژه « ascorbic acid » در نشریات گروه « شیمی »

Copper nanoparticles are widely used in various industries and products. Size and morphology are two important parameters to determine nanoparticle properties. In this study, copper nanoparticles were synthesized without an inert environment using two different reducing agents namely ascorbic acid and sodium hypophosphite. Various capping agents (PVP 105, PVP 4×104, PEG 6000, SDS, CTAB and glycerol) were used as stabilizers. Effect of several parameters including reducing agent concentration, type and amount of stabilizer and precursor concentration on the size and stability of the resulting nanoparticles have been investigated. The synthesis experiments resulted in a 25-60 nm average size of nanoparticles based on the synthesis conditions and the stabilizer type and concentration. Also this research provides a fast and simple way for the synthesis of stable pure colloidal copper nanoparticles in polyol, which is accomplished by decreasing CuSO4.5H2O using sodium hypophosphite in glycerol and without inert medium and homogeneous and non-agglomerated, 25 nm copper nanoparticles were obtained. The as synthesized copper nanoparticles are characterized using scanning and transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering techniques.

In this work, an easy method was employed to successfully develop La3+-doped ZnO nanoflowers and Guar-Gum (GG) modified screen printed electrode (La3+/ZnO/GG/SPE), and La3+/ZnO/GG/SPE was applied for the electrochemical detection of Ascorbic Acid (AA). The electrochemical methods, such as Cyclic Voltammetry (CV), chronoamperometry (CHA), and Differential Pulse Voltammetry (DPV) were used to evaluate the electrochemical performances toward ascorbic acid on the La3+/ZnO/GG/SPE. Good linear-ship was observed for ascorbic acid in the ranges of 1.0–700.0 μM, with the detection limits of 0.03 μM. Moreover, this sensor proved favorable to simultaneously determine ascorbic acid and acetaminophen. Finally, the modified electrode has fairly good performance during the employment of real sample analysis to determine the content of ascorbic acid. These results indicate that the La3+-doped ZnO nanoflowers are supposed to be a promising material in the electrochemical determination of ascorbic acid and acetaminophen in real samples.

This paper covers the synthesis and characterization of tetraamino Zinc(II) metallophthalocyanine (Zn(II)TAPc) using spectroscopic and electrochemical techniques. The electrochemical determination of dopamine (DA), ascorbic acid (AA) and uric acid (UA) was investigated using composite modified MWCNT-Zn(II)TAPc/GCE, due to their excellent conductivity, electrons transfer ability compared to the bare glassy carbon electrode (GCE), and because the charge transfer rate increases with multiwalled carbon nano tubes (MWCNT) on the surface of GCE. As a result, electrochemical sensing of bioanalytes was investigated on MWCNT-Zn(II)TAPc/GCE, and the analytical profile of micro molar concentration (µM) of DA is in the linear range of 0.1 to 1.1 µML-1 with LOD is 0.033µML-1, sensitivity of 14.063 µAµML-1 and the electro analytical sensing of AA and UA while using modified composite electrode for AA the linear range of 0.2-0.7 μmol L−1, LOD of 0.066μmol L−1 and sensitivity  54.821 μAμM−1 cm−2, for UA the linear range of 0.05–1.2 μmolL−1, lower detection limit of 0.066 μmolL−1 and sensitivity of 0.515 μAμM−1 cm−2, The MWCNT-Zn(II)TAPc/GCE shows good repeatability, stability and reproducibility.

In this research, the electrochemical performance of carbon paste electrode modified with 4-(3,5-dimethyl-1,4,7,8-tetrahydrodipyrazolo[3,4-b: 4', 3'-e] pyridin-4-yl)benzene-1, 3-diol (DBC) and zirconium dioxide nanoparticles (ZrO2) are investigated for the electrocatalytic oxidation of β-nicotinamide adenine dinucleotide (NADH). The kinetic parameters, transfer coefficient (α), and apparent charge transfer rate constant (ks) were obtained 0.31 and 4.83 s-1, respectively by the cyclic voltammetry (CV) technique. The anodic peak potential of the DBC modifier depends on pH and has a linear range with a slope of 0.047 V/pH. Also, the performance of the modified electrode in the electrocatalytic oxidation of NADH is investigated. It was observed that in the presence of the modifier, the overvoltage related to the oxidation of NADH decreases significantly and its oxidation potential decreases by about 300 mV. Also, the diffusion coefficient (D) between the species and the electrode surface was calculated (D=1.93×10-6 cm2 s-1) using the chronoamperometric method. Using the differential pulse voltammetry method (DPV), the detection limit of 5.8 nM was acquired. Two linear concentration ranges of 0.01-1.0 µM and 1.0-350.0 µM for NADH were obtained. The modified electrode was used to quantitatively analyze NADH in the blood serum sample. Also, this electrode can be acceptably utilized for the simultaneous measurement of NADH and ascorbic acid species.

In this study, the surface of the glassy carbon electrode (GCE) is modified with the nanocomposite of graphene oxide (GO)/ ionic liquid (1-Butyl-3-methylimidazolium tetrafluoroborate; [BMIM]BF4). The electrochemical behavior of ascorbic acid (AA) and dopamine (DA) at the surface of the modified glassy carbon electrode was studied using the differential pulse and cyclic voltammetric methods (DPV and CV). The results show good response sensitivity to AA and DA. The acceleration of the electron transfer rate and enhancement of the electroactive surface area is obtained due to a synergistic effect in the concurrent presence of GO and [BMIM]BF4 at the surface of the electrode. The presence of GO caused to a higher specific surface of the electrode, and ionic liquid ([BMIM]BF4) increased the ion conductivity and dispersibility in the modifier layer at the surface of the GCE. These results obtained in optimum conditions, show good peak separation for AA and DA (more than 300 mV), and the sub-micromolar detection limits for them. The obtained results in this work, make the modified GCE very effective in the manufacture of simple devices for the detection of AA and DA in human urine samples.

Fe is an important element, used in soft magnetic materials (cores) in electrical and electronic devices and its concentration in e-waste is high. Thus, this study is aimed to recover Fe from the soft magnetic FeSiAl cores of spent printed circuit boards (PCBs). Here, the Fe-rich FeSiAl cores were identified, separated manually, and subjected to dissolution in citric acid (100 mM) and ascorbic acid (10 mM) mixture at 80 °C. The dissolved Fe was selectively precipitated as Fe3O4 using 20% NaOH in an N2 atmosphere at 90 °C for about 60 min. The obtained Fe3O4 shows ferromagnetic behavior with 30 emu/g saturation magnetization at 300 K. The BET surface area of Fe3O4 NPs was found to be 71.656 m2 g-1. Furthermore, the Fe3O4 NPs were utilized for methylene blue degradation with H2O2 in visible light irradiation. At optimum conditions, such as 10 ppm MB solution, 0.1 mL H2O2, and an S:L ratio of 0.05 g/L about 100% degradation was achieved in about 45 min under visible light irradiation and the correlated rate constant is 0.084 min-1. We believe that the synthesis of value-added compounds directly from the dissolution medium is an environmentally benign step toward resource recycling.

This study reported a electrochemical sensor based on molecularly imprinted polymer (MIP) for simultaneous and selective detection of Ascorbic acid (AA) and Tyrosine (Tyr). The MIP film was electropolymerized on the glassy carbon electrode (GCE) using of o-aminophenol (o-AP) and m-dihydroxy benzene (m-DB) as monomers and the dual analyte of AA and Tyr, and its electrochemical performance was evaluated. Influencing parameters such as the pH value, electropolymerization cycle numbers, and template/monomer ratio were optimized. The differential pulse voltammetry (DPV) technique was used for the simultaneous and individual determination of AA and Tyr in their binary mixture. The introduced sensor showed the linear concentration ranges of 0.1-300 µM for AA and 0.01-180 µM for Tyr and good limits of detection were 0.03 µM and 0.003 µM, respectively. The proposed sensor was successfully employed to detect AA and Tyr in real samples. The recoveries were from 97 to 105% and the RSD was less than 3.5% which exhibited the usability of this sensor in the real sample.

The precipitation method was utilized to prepare MgO nanoparticle (MgO/NPs) without using surfactant in this study, the MgO/NPs was examined by XRD, SEM, and EDS analysis. The MgO/MCPE was developed and used for the oxidation of paracetamol (PA) in presence of ascorbic acid (AA) study by using cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. Finally, the developed sensor shows good electrocatalytic performance in pH and scan rate studies. From the concentration study for the voltammetric determination of PA, the limit of detection was found to be 4.33 µM for PA at MgO/MCPE, the practical purpose of the MgO/MCPE was utilized to evaluate PA in real sample analysis.

DFT calculations was applied for modelling ascorbic acid in three homologous sulfoxides solvents including methyl, ethyl, and propyl groups using 6-31++G** basis sets in B3LYP level. NBO analysis was performed to evaluate Mulliken charge, electron donor and acceptor in AA/DRSO system. Vibrational analysis was evaluated by Gaussview package for the normal modes and hydrogen bonds between hydroxyl groups of AA and sulfoxide group in the solvent. Our calculation showed that DFT/B3LYP method with 6-31++G** basis set is good candidate for quantum calculation of AA/DRSO systems. It was found that the most changes of the bond length were obtained in the interaction region between AA and the solvent, especially hydrogen bonds between oxygen of S=O group of sulfoxide and hydroxyl groups located on lactan ring. Charge analysis indicated that the positive charge of sulphur decreases by increase of alkyl group. Charge transfer (q) and polarity of S=O bond in DESO were higher than the other solvents. Vibrational analysis showed that the strongest hydrogen bond is formed in AA/DESO system.

Cobalt ferrite nanoparticles (CFNs) were successfully synthesized by a wet chemical method. The morphology and that of the crystal structure of the synthesized nano ferrites was done by X-ray diffraction analysis and Transmission electron microscopy techniques. The crystalline size of the synthesized nanoparticles was in the range of 30 nm calculated by the Debye-Scherrer equation. A glassy carbon electrode (GCE) modified with the ferrite nanoparticles (CFNs) was employed for the electrochemical detection of dopamine using the techniques of cyclic voltammetry and differential pulse voltametry. The chemically modified electrode exhibited exceptional redox action for the detection of dopamine (DA), with a notable decline of overpotential while compared to bare GCE. The CFNs/GCE exhibited excellent stability, reproducibility and sensitivity in the determination of DA with a detection limit of 0.2 μm. The sensor exhibited appreciable electrocatalytic behavior in the simultaneous detection of ascorbic acid (AA), Dopamine (DA) and Uric acid (UA).

Reduced graphene oxide was estimated for the modification of a glassy carbon electrode. The fabricated electrode was employed for folic acid determination in 0.1 M KCl solution (pH 14) using cyclic, linear sweep, differential pulse voltammetric and chronoamperometric techniques. The modified sensor exhibits a high electro-catalytic activity towards FA oxidation in the presence of ascorbic acid. The anodic peak current (IP) of FA increased linearly with an increase in pH (12.6–14) and scan rate (20–500 mV/s) at the ERGO/GCE. Good linearity was obtained between IP and FA concentrations (3.01–7.23 µM) with the detection (LOD) and quantification (LOQ) limits are 4.68 and 15.6 nM, respectively. Under diffusion control, the diffusion coefficient was estimated to be 2.88×10−6 cm2/s at the ERGO/GCE. The fabricated sensor gives high selectivity, good sensitivity and excellent reproducibility. Thus, the proposed method could be applied to detect FA in pharmaceutical formulations and urine samples.

The glassy carbon electrode (GCE) was modified with sunset yellow (SY) food dye to develop a simple, environmentally friendly, low-cost electrochemical sensor. The electrode performance as a useful sensor was demonstrated in the simultaneous and selective measurement of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The SY dye was covalently fixed on the electrode surface. The structure and morphology of the modified electrode were investigated by scanning electron microscopy (SEM), and the results showed that SY particles were located on the surface of the GC electrode. The electrochemical activity of the modified electrode was measured using cyclic voltammetry (CV), chronoamperometry, chronocoulometry, and impedance spectroscopy (EIS) techniques. The results showed that under optimal conditions, the SY/NaOH-treated-GCE has good electrocatalytic activity, a suitable linear range (7-320, 0.2-45, 0.2-50 µM), low detection limit (4.78, 0.12, 0.12 µM) for AA, DA, and UA respectively, and high stability. Analytical application of SY/NaOH-treated-GCE was successfully evaluated to determine AA, DA, and UA in bell pepper, grapefruit, dopamine ampoule, vitamin C tablet, tap water, and biological samples ( human blood and urine ). The results obtained by our team show that the SY/NaOH-Treated-GCE is suitable for simultaneous and selective measurement of electroactive species in various biologic and pharmaceutical samples.

A selective and sensitive voltammetric sensor was constructed using a Poly(methyl orange)/glassy carbon electrode (PMO/GCE). The PMO/GCE sensor was applied to investigate the electrochemical behavior of ascorbic acid (AA) and vitamin B2 (VB2) in PBS buffer solution. The sensor was applied for individual and simultaneous determination of AA and VB2using cyclic and differential pulse voltammetry (DPV) techniques. Different experimental parameters including scan rate(25-500 mV/s), pH (4-8 for AA and 3-10 for VB2) and analyte concentration (10-40 µM for AA and 4-85 µM for VB2) have been studied and optimized. High electrocatalytic activities for AA and VB2 oxidation were achieved at pH 7.0 and 6.0, respectively. In addition, results denoted that the oxidation process of AA and VB2 was under diffusion control. The respective detection limits, quantitation limits and linear ranges were 0.575, 1.916 and 10-40 μM for AA and 0.922, 3.073 and 5-85 μM for VB2under the optimized DPV conditions. Peak separation of AA from VB2was 660 mV which is enough to determine these vitamins simultaneously. The fabricated sensor has been applied successfully for estimation of AA and VB2 in real samples with good selectivity, stability and reproducibility.

In this study a new method for electrocatalytic oxidation and determination of ascorbic acid (AA) was developed. The proposed electrode was a zeolite-modified carbon paste electrode, which was doped with Ni (II) ions (Ni2+Y/ZMCPE). Ni (II) ions were doped in Y-zeolite framework by ion-exchange mechanism and actd as catalyst to oxidize ascorbic acid. Then, electrocatalytic oxidation of ascorbic acid, using cyclic voltammetry and chronoamperometry techniques was investigated. The diffusion coefficient and current density of ascorbic acid were calculated as 1.491×10-4 cm2 s−1 and 5.17×103 respectively. A linear dynamic range for determination of ascorbic acid and detection limit using proposed modified electrode were  0.02– 4.10 mmolL−1 and 2.8×10−6mol L−1 respectively.

For the first time, an analytical methodology based ondifferential pulse voltammetry (DPV) at a glassy carbon electrode (GCE) assisted by two multivariate calibration (MVC) models including back propagation-artificial neural network (BP-ANN), non-linear class, and partial least squares-1 (PLS-1), classical class, thatthey have been constructed on the basis of non-bilinear first order differential pulse voltammetry (DPV) data,was developed and validated for the simultaneous determination of Ascorbic acid, Uric acid, Acetaminophen, and Noradrenalinto identify which approach offers the best predictions.The baselines of the DPV signals were corrected by asymmetric least square spline regression (AsLSSR) algorithm. Before applying the PLS-1,lack of bi-linearity was tackled by potential shift correction using correlation optimised warping (COW) algorithm. The multivariate calibration (MVC) model was developed as a quaternary calibration modelin a blank human serum sample (drug-free) provided by a healthy volunteer to regard the presence of a strong matrix effect which may be caused by the possible interferents present in the serum, and it was validated and tested with two independent sets of analytes mixtures in the blank and actual human serum samples, respectively.According to the obtained results, the PLS-1 was recommended for simultaneous determination of AA, UA, AC, and NA in both blank and actual human serum samples .

Copper Sulfide (CuS) has received significant interest due to its attractive physical and chemical properties. In this study, the development and characterization of nano CuS (a p-type semiconductor with a bandgap of 1.2~2 eV) for the detection of ascorbic acid (Vitamin C) is reported. Nano CuSwassynthesized hydrothermally by studying the effects of cationic and anionic surfactants (CTAB and SDS). The as-synthesized nanostructures were characterized for surface morphology, chemical composition, and crystal structure. The developed CuS nanoparticles were then drop-cast on a graphite electrode and subjected to the electrochemical detection of ascorbic acid. Further, the deposition time of the analyte and the deposition potential of the electrode was evaluated. It was observed that the time required for ascorbic acid to deposit on the electrode was 20 seconds and deposition potential was found to be 0.34V. Besides, the effect of analyte concentration on the sensing ability of the nanomaterial was studied and a linear relationship between the two was observed. The working pH was found to be 9.4.

In the presented study, for the first time, simultaneous electrochemical measurements of ascorbic acid (AA), melatonin (Mel), and tryptophan (Trp) were discussed. The CuO-CeO2-rGO-MWCNTs nanocomposite was prepared, then applied for amendment of glassy carbon electrode (GCE) surface to the measurement of target analytes using differential pulse voltammetry (DPV) technique. Electrical impedance spectroscopy (EIS) techniques displayed that CuO-CeO2-rGO-MWCNTs/GCE has the lowest electron transfer resistance (Rct) in comparison to GCE and was suitable for electrochemical applications. The synthesized compounds were analyzed by powerful methods including Scanning Electron Microscopy (SEM) and, X-ray Diffraction (XRD). At the CuO-CeO2-rGO-MWCNTs/GCE, three oxidation peaks appeared at 0.309, 0.631, and 0.855 V for AA, Mel, and Trp and the peaks separation of ΔEp (AA and Mel)=322 mV, and ΔEp (Mel and Trp)=224 mV in the electrochemical potential window of 0.0-1.1 V. In optimum DPV condition and pH=5.0, a dynamic range of AA (0.01-28 µM), Mel (0.01-12.6 µM) and Trp (0.01-13.5 µM) with the detection limit of 9, 8 and 7.3 nM for AA, Mel, and Trp, respectively, were acquired. The provided modified electrode was successfully used to monitor the analytes in human biological fluids.