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Xi L.,Zhejiang University | Ren D.,Zhejiang University | Luo J.,Zhejiang Institute for Food and Drug Control | Zhu Y.,Zhejiang University
Journal of Electroanalytical Chemistry | Year: 2010

The electrosynthesis of polyaniline (PANI) film has been achieved on glassy carbon electrode (GCE) in a novel ionic liquid medium by means of cyclic voltammetry (CV). Then a copper nanoparticles (Cu-NPs) film was in situ electrochemically deposited on the surface of PANI/GCE. Electrochemical behavior and surface characteristics of the Cu-NPs/PANI/GCE were studied using cyclic voltammetry, scanning electron microscopy (SEM) and the results confirmed the presence of PANI and Cu-NPs on the electrode surface. Cu-NPs were highly dispersed and firmly stabilized by surface attachment of the PANI, which was prepared in ionic liquid and strongly attached to the electrode surface. The Cu-NPs/PANI/GCE showed excellent electrocatalytic activity toward the oxidation of ascorbic acid (AA) under weakly basic conditions. Amperometry was carried out to determine the concentration of AA at 0.2 V, and a good linear concentration range from 0.005 to 3.5 mM was found. The Cu-NPs/PANI composite film on GCE surface showed good reproducibility and stability. © 2010 Published by Elsevier B.V. Source

Zhu B.,Zhejiang Institute for Food and Drug Control | Ryan D.K.,University of Massachusetts Lowell
Journal of Environmental Radioactivity | Year: 2016

The development of chemometric methods has substantially improved the quantitative usefulness of the fluorescence excitation-emission matrix (EEM) in the analysis of dissolved organic matter (DOM). In this study, Regional Integration Analysis (RIA) was used to quantitatively interpret EEMs and assess fluorescence quenching behavior in order to study the binding between uranyl ion and fulvic acid. Three fulvic acids including soil fulvic acid (SFA), Oyster River fulvic acid (ORFA) and Suwannee River fulvic acid (SRFA) were used and investigated by the spectroscopic techniques. The EEM spectra obtained were divided into five regions according to fluorescence structural features and two distinct peaks were observed in region III and region V. Fluorescence quenching analysis was conducted for these two regions with the stability constants, ligand concentrations and residual fluorescence values calculated using the Ryan-Weber model. Results indicated a relatively strong binding ability between uranyl ion and fulvic acid samples at low pH (log K value varies from 4.11 to 4.67 at pH 3.50). Fluorophores in region III showed a higher binding ability with fewer binding sites than in region V. Stability constants followed the order, SFA > ORFA > SRFA, while ligand concentrations followed the reverse order, SRFA > ORFA > SFA. A comparison between RIA and Parallel Factor Analysis (PARAFAC) data treatment methods was also performed and good agreement between these two methods (less than 4% difference in log K values) demonstrates the reliability of the RIA method in this study. © 2015 Elsevier Ltd. Source

Deng M.,Zhejiang Medical College | Cheng W.,Zhejiang Institute for Food and Drug Control
Asian Journal of Chemistry | Year: 2015

Bioactivity-guided isolation and purification of EtOAc layer of Chrysanthemum maximum resulted in six components, among which four were flavonoids and two were phenolic acids. These components were identified to be isoquercitrin (1), hyperin (2), chlorogenic acid (3), caffeic acid (4), quercetin (5) and isorhamnetin (6) through physicochemical properties. The compounds 1-3 and 5 were all isolated from the plant for the first time and tested for their relative bioactivities. © 2015, Chemical Publishing Co. All rights reserved. Source

Chen X.,Zhejiang University | Han C.,Hangzhou Normal University | Cheng H.,Hangzhou Normal University | Wang Y.,Hangzhou Normal University | And 3 more authors.
Journal of Chromatography A | Year: 2013

In this work, a hybrid method for the rapid speciation of mercury compounds by cation exchange chromatographic separation and inductively coupled plasma mass spectrometry (ICP-MS) detection is reported. Effective separation of inorganic mercury (Hg2+), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) within 2-2.5min was achieved on two consecutive 12.5-mm strong cation exchange guard columns with 2.0mM l-cysteine or thiourea (pH 2.0) as the mobile phase. This separation met the requirements of green analytical chemistry such as the prevention of toxic waste, safer HPLC mobile phases, and short separation times to reduce operating costs. The detection limits for Hg2+, MeHg, EtHg and PhHg were 0.019, 0.027, 0.031 and 0.022μgL-1, each, and the repeatabilities of peak height and peak area (5.0μgL-1 for each Hg species) were all lower than 3%. Contents of Hg species and total mercury in certified reference materials of seawater (GBW(E) 080042) and fish tissue (GBW 10029) were in good accordance with the certified values, and satisfactory recoveries (96-102% for GBW(E) 080042 and 94-101% for GBW 10029) validated the developed method. The developed method was applied for the speciation of mercury in five seawater sample and five marine fish samples. The concentrations of mercury species in all analyzed fish samples did not exceed the permissible levels of the National Standard of China. © 2013 Elsevier B.V. Source

Zeng L.,Zhejiang University | Kong H.,Zhejiang University | Zhu M.,Zhejiang Institute for Food and Drug Control | Yan W.,Zhejiang University
Journal of Functional Foods | Year: 2016

Platycodi Radix, the root of Platycodon grandiflorum A. De Candolle, is a widely used functional food in East Asia. Reference standard extract, a mixture of marker compounds, is used as a reference substance to quantify platycosides from Platycodi Radix. The convenience and consistency of using reference standard extract as a reference substance was evaluated. The qualitative and quantitative results of platycoside contents in Platycodi Radix characterized by this method were compared with that characterized by the conventional external standards method. The Pearson correlation coefficient test of these two methods was between 0.985 and 0.999. A more comprehensive chemical information including relative retention time, relative peak area and contents of active components were obtained simultaneously from raw material using reference standard extract method. The application of this method may relieve the stress in increasing demands for pure marker compounds. © 2016 Published by Elsevier Ltd. Source

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