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A Hydrogen Peroxide Sensor Based on Palladium Nanoparticles Loading to Poly(amidoamine) Dendrimers Functionalized Carbon Nanotubes

Yanjun ZHANG ; Xiuhui LIU ; Juanjuan LU ; Hongwei WEI ; Xiaoquan LU

Chinese Journal of Analytical Chemistry.2016;44(9):1402-1409. doi:10.11895/j.issn.0253-3820.160170

The fourth generation poly( amidoamine) dendrimers ( G4. 0 PAMAM) functionalized multiwalled carbon nanotube ( G4 . 0-MWCNTs ) was prepared by amidation between carboxylated multiwalled carbon nanotube (MWCNTs) and G4. 0 PAMAM. Then a novel hydrogen peroxide (H2O2) sensor was fabricated by electrodepositing Pd nanoparticles (NPs) on a glassy carbon electrode (GCE) modified with G4. 0-MWCNTs composites. The modified electrode was characterized by field emission scanning electron microscopy ( FESEM) , cyclic voltammetry ( CV) and electrochemical impedance spectroscopy ( EIS) . A large amounts of highly dispersion PdNPs could be well loaded on the surface of the G4. 0-MWCNTs, and the modified electrode exhibited excellent electrocatalytic activity towards the reduction of H2 O2 . Under the optimized conditions, the reduction peak currents of H2 O2 were linear to their concentrations in the range from 1. 0 × 10-9 mol/L to 1. 0×10-3 mol/L and the limit of detection of 2. 3×10-8 mol/L was obtained. The recovery of standard addition for human serum samples was 96 . 7%-103 . 1%.

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Determination of L-Tryptophan by Using Ordered Mesoporous Silica Modified Carbon Paste Electrode Based on Enhancement Effects of Surfactant

Yu YA ; Liping XIE ; Cuiwen JIANG ; Tianshun WANG ; Leixing MO ; Tao LI ; Feiyan YAN

Chinese Journal of Analytical Chemistry.2016;44(9):1394-1401. doi:10.11895/j.issn.0253-3820.160220

An ordered mesoporous silica ( OMS ) was synthesized through hydrothermal process. The synthesized material was characterized by different techniques such as X-ray diffraction, nitrogen adsorption-desorption and transmission electron microscope. The electrochemical characteristics of the OMS modified carbon paste electrode ( OMS/CPE ) were investigated by using cyclic voltammetry and electrochemical impedance spectroscopy. Compared with bare carbon paste electrode ( CPE ) , the OMS/CPE exhibited a larger electrode surface and a faster electron-transfer rate. Electrochemical behaviors and kinetic properties of L-tryptophan ( L-Trp) at the OMS/CPE in the presence of sodium dodecylsulphate ( SDS) were studied. The results showed that the voltammetric response of L-Trp at OMS/CPE was improved due to the synergistic effect of OMS and SDS. The electrochemical oxidation of L-Trp at OMS/CPE in the presence of SDS was an irreversible process involved two electrons and two protons, and the electrode process was controlled by the adsorption step. Some parameters such as SDS concentration, accumulation time, accumulation potential and pH were optimized. Under optimal conditions, the oxidation peak current was linearly proportional to L-Trp concentration in the range of 8. 0×10-8 to 4. 0×10-6 mol/L, with a detection limit of 7. 0×10-8 mol/L (S/N=3 ) . The proposed method was applied for the determination of L-Trp in oral liquid with the recoveries of 99 . 6%-102 . 6%.

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Synthesis of Novel Hapten and Development of Monoclonal Antibody-based Enzyme-Linked Immunosorbent Assay for Malachite Green in Fish Samples

Yu WANG ; Jinyi YANG ; Zhenlin XU ; Ping QI ; Yudong SHEN

Chinese Journal of Analytical Chemistry.2016;44(9):1385-1393. doi:10.11895/j.issn.0253-3820.160360

To produce specific antibodies against malachite green ( MG) , one special hapten was synthesized and characterized, and conjugated to carrier protein as immunogen. The immunogen showed excellent reactogenicity and immunogenicity. One specific monoclonal antibody (mAb, named MG-DA4-C7) with high sensitivity and specificity for MG in indirect competitive enzyme-linked immunoassay ( icELISA ) was screened. The isotype was IgG1 and the light chain was κ type. After optimization of ELISA conditions, the proposed icELISA showed a 50% inhibition value ( IC50 ) of 0. 96 μg/L, a linear range ( IC20-IC80 ) of 0. 1-8. 1 μg/L and a limit of detection ( LOD, IC10 ) of 0. 05 μg/L for determination of MG. The assay showed cross-reactivity of 18. 1%, 26. 5% with crystal violet and brilliant green, respectively, and negligible cross-reactivity with other metabolites of MG (<0 . 1%) . The average recoveries of MG from spiked fish samples were from 87. 3% to 107. 3%. Good correlation (R2=0. 999) was obtained between the results of icELISA and those of liquid chromatography-tandem mass spectrometry analysis. The proposed icELISA is suitable for the determination of MG in fish samples in a simple and sensitive manner.

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Mechanism of Lead Biosorption and Biotransformation in Lead-Resistant Bacteria by In Situ Synchrotron Radiation Micro X-Ray Fluorescence and X-Ray Absorption Near Edge Structure

Yuan ZENG ; Liqiang LUO

Chinese Journal of Analytical Chemistry.2016;44(9):1372-1377. doi:10.11895/j.issn.0253-3820.160080

To investigate the mechanism of lead biosorption and biotransformation in lead-resistant bacteria in microcosmic scale, synchrotron radiation micro X-ray fluorescence (μ-SRXRF ) and X-ray absorption near edge structure ( XANES) was used to determine the element distribution characteristics and speciation of lead ( Pb) in lead-resistant bacteria strain isolated from farmland soil samples taken from a lead-zinc mine in Lanping county, Yunnan province in China. The isolated species was identified to be Arthrobacter sp. The concentration of Pb biosorpted in lead-resistant bacteria was directly determined byμ-SRXRF, and the results showed that the highest concentration was 5925μg/g and the bioaccumulate factor was 14 . 8 . Speciation of Pb in lead-resistant bacteria B2, LB ( Lysogeny Broth) medium and soil were also presented after using Pb LⅢXANES. Compared with Pb LⅢ XANES peak shape and peak position between standard samples, it was demonstrated that the Pb in lead-resistant bacteria was mainly formed by amorphous forms like PbS (58. 0%), (C17H35COO)2Pb (22. 2%), Pb5(PO4)3Cl (19. 8%) rather than organic Pb speciation which was exist in LB medium. Therefore, the isolated lead-resistant bacteria could biotransform Pb to sulfuric compounds. The biotransformation regular could be of great interest for other investigators as reference in study of bioavailability impact factor of heavy metals.

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Fast Determination of Rare Earth Elements in Tea Samples by ICP-MS with Modified Oxygen Flask Combustion

Zhou ZHOU ; Junfang GUO ; Taicheng DUAN ; Kailun HUANG ; Jiagui NING

Chinese Journal of Analytical Chemistry.2016;44(9):1359-1364. doi:10.11895/j.issn.0253-3820.160348

A new method for accurate determination of 15 rare earth elements including Y-Lu in tea samples by inductively coupled plasma-mass spectrometry( ICP-MS) was proposed. Sample preparation was based on the modified oxygen flask combustion technique. By using quartz cloth coated with glycerol instead of filter paper as the ignition agent, a total amount of 0. 1 g sample could be completely burned in a 500-mL flask. Key factors affecting the sample preparation effect were systematically investigated, and it was found that the extraction efficiencies of over 90% for all the analytes could be realized with 5 mL of 4% HNO3+1% HF ( V/V) as the extractant for the combustion residue and the total extraction process could be finished in one minute under sonication, which resulted in a very fast sample preparation procedure that could be completed in less than 3 minutes. The relative standard deviations ( RSD) of six parallel determination values were between 2. 7% and 5. 5%, and the detection limits ranged from 0. 001 mg/kg to 0. 006 mg/kg. Three tea standard reference materials were analyzed with the method and the detection results agreed well with the standard values. The method was successfully applied to three real samples analysis.

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Analysis of Volatile Organic Compounds by Specific Carbon Stable Isotope

Jiani WANG ; Han ZHANG ; Zhenyu HONG ; Hui XU ; Xian ZHANG ; Jinsheng CHEN

Chinese Journal of Analytical Chemistry.2016;44(9):1342-1347. doi:10.11895/j.issn.0253-3820.160153

Theδ13 C values of volatile organic compounds ( VOCs) in various emission sources and ambient air were analyzed by using thermal desorption coupled with gas chromatography and isotope ratio mass. The lowest sample concentration and peak shape quality needed for high precision and accurate analysis were investigated. Fuel evaporation ( gasoline and diesel) , vehicle exhaust, solvent evaporation, dining fumes and ambient air of different functional zones of Xiamen city were collected using Tenax TA tube, and the significant differences in δ13 C values of VOCs between these sources were observed. The δ13 C value of gasoline exhaust ( 97 # ) was heavier (-25 . 84‰) than that of dining fumes (-30 . 26‰) and theδ13 C values of fuel evaporation were heavier than that of vehicle exhaust after combustion. The average δ13 C value of atmospheric VOCs in Xiamen was at the level of -27 . 03‰ to -25 . 40‰, which was close to the δ13 C value of the evaporation and exhaust of gasoline and diesel, indicating that the VOCs in the atmosphere of Xiamen was highly influenced by transportation related sources.

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Extensive Imprinting Adaptability of Polyacrylamide-based Amphoteric Cryogels Against Protein Molecules

Chun YANG ; Xinglu ZHOU ; Yaru LIU ; Yan ZHANG ; Jian WANG ; Lili TIAN ; Yanan YAN

Chinese Journal of Analytical Chemistry.2016;44(9):1322-1327. doi:10.11895/j.issn.0253-3820.160292

Lysozyme, pepsin, ovalbumin, hemoglobin andγ-globumin were chosen as templates to investigate the imprinting capability of amphoteric polyacrylamide cryogels. Prepolymerizing solutions contained acrylic acid and allyl amine, as well as acrylamide and N,N'-methylenebisacrylamide as the functional monomers. As a result there were both acidic and basic functional groups in the polymers, facilitating effective interactions with likewise amphoteric proteins. The proteins differ greatly and cover wide scopes of molecular weights and isoelectric points. Regardless of the values of the molecular weights and isoelectric points, all the templates gave higher retentions on the MIP tubes than on the NIP tube. The MIP of lysozyme indicated the highest imprinting factor of 7. 0, and that of γ-globumin showed the lowest, 2. 0. The values of other proteins were intervenient. Conclusively the amphoteric polyacrylamide cryogels were suitable imprinting materials for various proteins, and could potentially be used for protein recognition, purification, and depletion.

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Research on Thin Film type Hydrogen Sulfide Sensor Based on SnO2-CuO Nanofibers

Mingjiang HU ; Zhong WANG

Chinese Journal of Analytical Chemistry.2016;44(9):1315-1321. doi:10.11895/j.issn.0253-3820.160166

A SnO2-CuO composite nanofiber was prepared by the coaxial electrospinning method. A new thin-film-type hydrogen sulfide gas sensor was designed by coating SnO2-CuO composite nanofibers onto an alumina ceramic tube with Au electrodes by dip-coating method. The crystalline phase and microstructure of SnO2-CuO composite nanofibers were characterized using X-ray diffraction ( XRD ) and scanning electron microscope ( SEM) . The influence of chemical composition and thickness of sensitive film on the sensitive mechanism and electrochemical characteristic of SnO2-CuO nanofibers were analyzed. The characteristic tests of hydrogen sulfide sensor including sensitive performance, temperature, relative humidity, dynamic response, interference and stability were carried out by WS-30A type multifunction analyzer in gas sensor test system. The results demonstrated that, when the operating temperature was 25℃ and hydrogen sulfide gas concentration increased from 10 to 60 mg/L, the hydrogen sulfide sensor based on C50 composite nanofibers with 70 nm sensitive film thickness had the best linearity (92. 3%) and sensitivity (98. 2%). Besides, its highest response values and relatively humidity level were 1080 and 95%, respectively, and its dynamic response time and recover time were 4 s and 12 s, respectively. This sensor showed good anti-disturbance to the gases, such as CO, NO2 , SO2 , NH3 , CO2 , CH4 and H2 . The response value of the sensor was attenuated about 9. 2% when it was applied continually in the mine about 12 months, and its normal response time was 10. 9 months.

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Design and Implementation of Embedded Telemetry System for Amperometric Detection

Xiaogang LI ; Binqian GUO ; Taichun QIN ; Jie HAO ; Ping YU ; Lanqun MAO

Chinese Journal of Analytical Chemistry.2016;44(9):1465-1470. doi:10.11895/j.issn.0253-3820.160234

A new micro embedded telemetry system was developed for the amperometric sensing detection. Its output voltage range was ±0. 5 V and resolution was<1 mV. The current acquisition range was ±1μA and the minimum resolution was 0. 2 nA. This telemetry system was designed based on microprocessor ADuCM360, including a potentiostat, a current detection module and a radio module. And the size was only 24 mm × 13 mm × 11 mm. The computer software written in LabVIEW language was used for data storage and display. In order to verify the accuracy and reliability of this system, an electrical performance test was performed. The current response for ascorbic acid with different concentration was recorded by using the telemetry system. The potential of working electrode was set as 30 mV, and the current response of ascorbic acid electrode had a good linear relationship with its concentration within the concentration range of 50-300 μmol/L. Linear equation was I(nA) = 2. 98CAA(μmol/L)-137. 39, and linear correlation coefficient R2=0. 984. Moreover, the applicability of the instrument in the study for living animals was explored by using the cerebral ischemia as model.

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Synchronous Detection of Rat Neural Spike Firing and Neurochemical Signals Based on Dual-mode Recording Instrument

Shengwei XU ; Li WANG ; Xianteng SONG ; Song ZHANG ; Mixia WANG ; Ping YU ; Lanqun MAO ; Xinxia CAI

Chinese Journal of Analytical Chemistry.2016;44(9):1458-1464. doi:10.11895/j.issn.0253-3820.160108

A dual-mode recording system used for synchronous detection of neuroeletrical and neurochemical signals was developed, and a dual-mode synchronous detection experiment was carried out using the instrument. The device comprised 64-channel neuroelectricity recording module with voltage resolution of 0. 3 μV and 4-channel neurochemistry recording module with current resolution of 1 pA. The software had many basic features, including Spike separation and sort, chronoamperometry, cyclic voltammetry, etc. In particular, the software could observe and analyze the dual-mode neural signals synchronously. The performance of the system was demonstrated in the single mode detection experiments. In neuroeletrical experiments, 64-channel simulate neural signals were detected and the signal to noise ratio ( S/N) of Spike recorded from cortex of Sprague-Dawley ( SD ) rat was 6. In the K3 [ Fe ( CN )6 ] and ascorbic acid measurement experiments, the current response of K3 [ Fe ( CN)6 ] in the range of 0. 1-10 mmol/L was obtained by cyclic voltammetry, with a correlation coefficient of 0. 9889, and the current response of ascorbic acid ( concentration:10-800 μmol/L) by chronoamperometry increased linearly with a correlation coefficient of 0. 9841. Based on the rat model of global cerebral ischemia, a dual-mode detection experiment was carried out. In the experiment, the neuroelectrical and neurochemical signals were synchronously recorded in the SD rat primary visual cortex. According to the experimental results, we got the conclusion that the concentration of ascorbic acid negatively related to the Spike firing in the SD rat primary visual cortex.

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