Analytical Chemistry Commons^™

Study Of Electrochemistry Of Aloe-Emodin And Determination Of It With 1.5th Order Derivative Anodic Stripping Voltammetry, Xin Hua Lin, Li Ying Huang, Wei Chen, Hong-Bin Luo, Bin Qiu, Chun-Yan Li

Journal of Electrochemistry

In 0.1 mol/L HAc solution(pH=2.89),the voltammetric behaviours of aloe emodin at a glassy carbon electode has been studied. One pair of current peak of the voltammogram may be attributed to a quasireversible two electron transfer of aloe emodin molecules at the glassy carbon electrode. A new method, the derivative anodic stripping voltammetry, for aloe emodin determination is described. The adsorptive potential of aloe emodin is -0.80V(vs. SCE),while its stripping potential is -0.38V(vs.SCE). The peak current is propotional to the concentration of aloe emodin over the range of 2.0×10 -7 ～8.0×10 -6 mol/L. The method is simple, rapid and reliable for …

Analyses On Spm Images And Theoretical Investigations On Oxygen Vacancy Concentration Of Light-Induced Nanostructured Titania Super Hydrophilic Films, Ren-Jie Zeng, Zhong-Hua Lin, Zhi-Min Fang

Journal of Electrochemistry

A typical nanostructured titania super hydrophilic film was chosen for general characterization employing a Scanning Probe Microscope(SPM)and an electrochemical measurement system.Following from the principles of the solid state chemistry and nanomechanics,intensive theoretical. analyses on the SPM images,the oxygen vacancy concentrations and the mechanism of the super hydrophilicity were made;further illuminations on a reaction equation of titania defect formation,a tentative universal surface physical mode for the wet ability,a concept,amphiphobicity,and surface design were carried out after the author's previous introduction and proposal in the end of 1999.

Simultaneous Determination Of Enantiomers Of Structurally Related Anticholinergic Analogs In Human Serum By Liquid Chromatography–Electrospray Ionization Mass Spectrometry With On-Line Sample Cleanup, Vladimı́R Čápka, Yan Xu

Chemistry Faculty Publications

Trihexyphenidyl, biperiden and procyclidine are anticholinergic drugs produced as racemates for the treatment of Parkinson’s disease. This paper describes a simple and sensitive LC–MS method for the simultaneous determination of these compounds in human serum. An on-line sample clean-up procedure was used, where serum samples were directly injected into a “restricted-access media” pre-column. After the exclusion of the serum proteins, the drug molecules were eluted to a β-cyclodextrin analytical column for chiral separation. The quantitation was done by electrospray ionization MS using diphenidol as an internal standard. The method developed has limits of detection of 1 ng/ml, at least two-orders-of-magnitude …

A Cooperative Molecular Modeling Exercise— The Hypersurface As Classroom, Christopher J. Cramer, Bethany L. Kormos, Paul Winget, Vanessa M. Audette, Jeremy M. Beebe, Carolyn S. Brauer, W.Russ Burdick, Eric W. Cochran, Brian M. Eklov, Timothy J. Giese, Yongseok Jun, Lakshmi S.D. Kesavan, Christopher R. Kinsinger, Mikhail E. Minyaev, Ramkumar Rajamani, Jonathon S. Salsbury, John M. Stubbs, Jack T. Surek, Jason D. Thompson, Vincent A. Voelz, Collin D. Wick, Ling Zhang

Eric W. Cochran

Quantum chemistry has been a staple of undergraduate curricula for several decades. For the most part, however, it has been the rare course in quantum chemistry that advances much beyond the hydrogen atom (or perhaps H2) in terms of describing the electronic structure of real molecular systems. Driven in part by staggering advances in computer technology during the last 15 years or so, which have rendered possible on a laptop calculations that once would have taxed the largest mainframes available, this situation now seems to be changing (1–3).

In Situ Ftir Reflection Spectroscopy Of Bioelectrode, Sa-Ying Dong, Guang-Yu Zhao, Yuzhu Gao, Guang-Zhang Chen, Ming-Xiang Lv

Journal of Electrochemistry

In situ FTIR reflection spectroscopy was used to study mediated enzyme electrode and immunoelectrode. We determined and analyzed IR characteristic spectra of GOD and glucose by the use of potential difference spectra and single beam subtractive spectra. At last, we explored the IR absorption characters of enzyme_immunoelectrode.

Electrochemical Impedance Spectroscopy Study On A3 Steel In Anti-Corrosive Pigment Extract Solution, Zhi-Jun Gu, Yong-Gui Liao, Zhi-Gang Zhang, Qi-Long Guo, Fang-Teng Su, Wen-Yun Hu, Yan-Zhen Chen

Journal of Electrochemistry

The corrosion behaviors of A3 steel in different pH, 3.5%NaCl, modified zinc phosphate and aluminum triphosphate extract solutions have been studied by EIS. Results show:(a) The resistance increases with the increase of pH value under the same circumstances, but the capacity is the reverse.(b) Zinc phosphate, because of its low solubility, shows no inhibitive performance for A3 steel in 3.5% NaCl extract solutions. (c) Aluminum triphosphate has good inhibitive performance for A3 steel in 3.5% NaCl extract solutions at a pH of 6, probably because the triphosphate ion can complex with the corrosion_product, such as ferric and ferrous ions, and …

Simultaneous Determination Of Gold(Ⅲ) And Copper(Ⅱ) With Two-Way Stripping Voltammetry, Rong-Zong Hu, Dong-Ping Wei, Guang Wei, Yue-Ying Liu

Journal of Electrochemistry

A novel Two_way Stripping Voltammetry method for simultaneous determination of Au 3+ and Cu 2+ was reported in this paper. Because of the strongly electrostatic attraction of carbon paste electrode towards Au(Ⅲ) ion at positive potential and the biochemical contribution of Gram_positive bacteria strain DO1, the ion can be determined by cathodic stripping voltammetry. At the same time, Cu(Ⅱ) is reduced readily under the catalysis of ultra_fine gold particles, thereafter it can be determined by anode stripping voltammetry. There is no interference between the determination of Au 3+ and Cu 2+ . A perfect liner relationship between the concentrations of …

Determination Of Hydrogen Diffusion Coefficient In Metal Hydride Electrode With Electrochemical Impedance Spectroscopy, Xian Xia Yuan, Nai Xin Xu

Journal of Electrochemistry

Electrochemical impedance spectroscopy was employed to determine the hydrogen diffusion coefficient in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 metal hydride electrode with various states of charge(SOC) at room temperature and with 50% SOC at various temperatures. It was found that hydrogen diffusion coefficient in this electrode decreases with the increase in SOC at ambient temperature, and for the electrode with 50%SOC, hydrogen diffusion coefficient increases with the increase of temperature and the activation energy for hydrogen diffusion in it is 35 kJ/mol.

Comparison In Surface Enhanced Raman Scattering On Salicylideneamine Between Silver And Gold Colloid And Silver Mirror Substrate, Zhao Bing, Yukihiro Ozaki

Journal of Electrochemistry

In recent years, the study of photochromic and thermochromic materials has grown because of their possible applications in the optical processing of information, in addition to the scientific interest. Salicylidineaniles is one of the prospective choices owing to their photochromism caused by intramolecular hydrogen transfer [1～3] (Fig.1). It is generally agreed that, in the salicylideneamine system, photoexcitation is followed by a rapid barrierless proton transfer and subsequent rearrangement to form a colored photoproduct [4] . The photochemistry of the system in fluid solution is different from that of the solid, even in fluid solution, the photo? and thermo?chromic behavior is …

The Dependence Of Relative Enhancement Of Sers Bands On Temperature, Ling Huang, Jian Shen, Tsing Yu, Qing-Jin Meng

Journal of Electrochemistry

The adsorption and binding behavior of 2,5_dimercapto_1,3,4_thiadizole(DMTD) on silver surface was studied by near_infrared Fourier Transfer surface enhanced Raman scattering(NIR FT-SERS) technique. It was found that the relative intensities of the SERS bands change regularly with the increasing of temperature, which suggests the transformation of the tautomers or the re_orientation of DMTD molecules in the surface layer.

Computer Simulations Of Confined Systems, Jayendran C. Rasaiah

University of Maine Office of Research Administration: Grant Reports

Jayendran Rasaiah of the University of Maine is supported by an award from the Theoretical and Computational Chemistry program with partial funding provided by the Experimental Program to Stimulate Competitive Research for the development of computational methods to simulate water and other solvents in confined systems, such as carbon nanotubes and the interior of proteins. Other systems which are being studied include capillary evaporation of water between hydrophobic plates, water near surfaces and water between charged membranes. The development of better water potentials for a variety of applications is a major goal of the research. Rasaiah is also developing efficient …

Determination Of Lysophosphatidic Acids By Capillary Electrophoresis With Indirect Ultraviolet Detection, Yi Lung Chen, Yan Xu

Chemistry Faculty Publications

Lysophosphatidic acid (LPA) is the simplest form of lysophospholipid. Molecular species of LPA have been identified as the potent components in the ovarian cancer activation factor. The elevated plasma LPAs may be used as potential biomarkers for the early detection of ovarian cancer. This paper is the first report on the quantitative analysis of molecular species of LPA using capillary electrophoresis. In this work, the separation of LPAs was achieved within 14 min in an adenosine monophosphate-borate–methanol–water solution, and the measurement was accomplished by indirect UV detection. With LPA (D) as internal standard, the method had linear calibration ranges for …

The Applications Of Confocal Raman Micro-Spectroscopy For Study Of Practical Electrode Materials, Yang Y, Chu W, Nan J M, Chen X G, Lin Z G

Journal of Electrochemistry

Some recent research work about applications of confocal Raman micro spectroscopy for study of practical electrode materials carried out in our lab has been briefly introduced. The examples include study of electrochemical Li + intercalation process, characterization of surface oxide film on AB 5 type electrodes and passive film and pitting corrosion of Rebar electrodes.

Raman And Afm Characterization Of Au And Cu Nanorod And Nanowire Arrays, Jing Tang, Jian Lin Yao, Kuan Hong Xue, De-Yin Wu, Long-Gang Lin, Yu-Xiong Jiang, Bin Ren, Xin Xu, Bing Wei Mao, Zhong Qun Tian

Journal of Electrochemistry

Recently metal nanowires (nanorods) have aroused tremendous interest because of their novel properties and potential applications in wide fields [1] . Many two?dimensional nanowire arrays of semiconductors and metals with different diameter and length have been made by using template synthesis method. To characterize the novel optical, electronic and magnetic properties of these materials, UV?Vis and fluorescence spectroscopies are two of the most wildly used methods [2, 3] . Raman spectroscopy has, however, only been applied to the characterizing of semiconductor nanowires and carbon nanotubes [4,5] . Important and meaningful information can be obtained in these cases, as some forbidden …

Surface-Enhanced Raman Spectroscopy Of Metallotetraphenyl Porphyrins Adsorbed On Ag_2o And Silver Colloids, Ying Hui Zhang, Dong Ming Chen, Tian Jing He, Fan-Chen Liu

Journal of Electrochemistry

The biological significance of porphyrins and metalloporphyrins has stimulated intensive investigations on these compounds for many years. On the other hand, porphyrins and metalloporphyrins also have extensive applications in many other fields such as chemical modified electrodes, organic photovoltaic devices and biomimetic catalysis. The adsorption behavior and chemical reactions of metalloporphyrins on surfaces or interfaces are very important for these applications. Surface?enhanced Raman spectroscopy has been used to investigate the physical and chemical processes of the porphyrins on surfaces in many scientific publications. Surface?reactions such as metalization, demetalization, aggregation, electrochemical redox and N?protonation of the porphyrins on colloids, electrodes or …

Raman Spectroelectrochemical Study On Bioactive Molecules, Xiao-Wei Cao, Hai Feng Yang, Zhe Su Meng Xiao Yun Wang, Xia Qin Wu, Zong-Rang Zhang

Journal of Electrochemistry

Electron?transfer reaction is known to be one of the key reactions for generating biological functions. Mechanism revelation at a molecular level of such kind reactions is to be very helpful for us to understand life essence. In fact, surface enhanced Raman scattering (SERS) is one of the most powerful tools for the study on metal?electrolyte and metal?vacuum interfaces since 1970's. Moreover, Raman spectroscopic study in enzymology has provided attractive results during last twenty?five years. For the study of electron?transfer reaction mechanism of some oxidoreductases and SERS of some other biological macromolecules, an electrochemical in situ Raman spectroscopic technique was established …

Two-Dimensional Surface Raman Imaging Of A Roughened Iron Electrode In Saline Water, Pei-Gen Cao, Jian Lin Yao, Jun Wei Zheng, Bin Ren, Ren-Ao Gu, Zhong Qun Tian

Journal of Electrochemistry

The analysis of the composite and distribution of iron oxide due to pit corrosion in saline solutions (3.4% NaCl) is of great importance. Many electrochemical methods, XPS, and other photoelectronic techniques have been applied to this domain. Surface?enhanced Raman scattering (SERS) spectroscopy can provide the vibrational information of surface species with high sensitivity and is very useful in the study of surface chemistry of iron. Notwithstanding, the application of SERS in iron corrosion is hampered for its SERS?inactivity. Efforts have been devoted to extend the use of SERS to the study of iron. Approaches include the deposition of particles or …

Adsorption And Oxidation Of Ethanol On Nm-Pt/Gc Electrode Ii. Eqcm And In-Situ Ftir Spectroscopic Studies In Acid Media, Guo Liang Chen

Journal of Electrochemistry

The adsorption and oxidation of ethanol on nm?Pt/GC electrode in acid solutions containing 0.1 mol·L -1 H 2SO 4 +0.1 mol·L -1 CH 3CH 2OH was investigated by using cyclic voltammetry , EQCM and in?situ FTIR spectroscopy. The experimental results demonstrated that the oxidation of CH 3CH 2OH is closely relaed to solution acidity and oxygen species on electrode surface; CH 3CH 2OH was oxidized on nm?Pt/GC electrode in acidic media via a dual path reaction mechanism, i.e . CH 3CH 2OH may be oxidized into CO 2 through the dissociative adsorbate (CO) and the reactive intermediates that were determined …

Confocal Microprobe Raman Spectroscopy For Investigating The Electrochemical Interface, Bin Ren, Feng Ming Liu, Xufeng Lin, Zhong-Qun Tian

Journal of Electrochemistry

The invention of the surface enhanced Raman spectroscopy (SERS) in the mid of 1970s, opened an entirely new and very promising area. However, it was found that SERS of practical application in electrochemistry can only be found on noble metal surfaces, such as Ag, Au and Cu that exhibit huge surface enhancement [1] . This greatly limits the application of SERS in electrochemistry. In electrocatalysis, corrosion inhibition, sensor, and power source, the most widely used materials are Pt, Fe and Ni and their alloys as well as Si. Thus, it is of great significance to extend surface Raman study to …

Electrochemical Impedance Spectroscopy Studies On Inhibitive Performance Of Aluminum Triphosphate Pigment, Yonggui Liao, Zhijun Gu, Zhigang Zhang, Qilong Guo, Fang-Teng Su

Journal of Electrochemistry

The epoxy coatings on A3 steel sheets containing calcite or aluminum triphosphate (AlTP), were investigated by Electrochemical Impedance Spectroscopy (EIS). The results showed that calcite pigment is not an inhibitor, but an extender pigment, and that AlTP pigment can considerably enhance the protective performance of epoxy coating. The triphosphate ion at the interface between the steel substrate and the coating can complex with the corrosion product, such as ferric and ferrous ions, and form a compact protective film which effectively separates the steel substrate from the aggressive media.

Rhodium As A Ubiquitous Substrate For Surface Enhanced Raman Spectroscopy, Bin Ren, Xu Feng Lin, Zhong Qun Tian

Journal of Electrochemistry

Raman Spectroscopy is a powerful technique in characterizing the molecular structure at the molecular level. However, only after the discovery of surface enhanced Raman scattering (SERS) effect, has it become one of the most widely used technique in surface sciences. The limitation that only Ag, Au and Cu can produce prominent SERS signal of practical significance, greatly hinders the application of this technique. Recently our group has made great progress in extending SERS to pure transition metal surfaces, such as Pt, Ni, Fe, Co etc [1] . Rh, due to its special application as catalysts in the catalytic or electrochemical …

In Situ Raman Spectroelectrochemical Characterization Of The Prussian Blue/Platinum Modified Electrode, Xiao-Wei Cao, Rong Wang, Gui Hua Wang, Zong Rang Zhang

Journal of Electrochemistry

Prussian Blue is known to be deposited electrochemically on the electrode surface, producing a dense redox active layer. Since the Prussian Blue modified electrode was first reported by Neff in 1978 [1] , different in situ spectroelectrochemical techniques have been widely used to investigate its electrochemical mechanism [2～4] . But no research work related to the in situ Raman spectroscopic studies on it has been reported. In this paper we try to characterize the nature of thin Prussian Blue films on platinum substrates with in situ Raman spectroelectrochemical technique. A Super LABRAM confocal microscopic Raman spectrometer (Dilor) with a He?Ne …

The Charge Transfer Effect Of Sers Induced By The Electrochemical Hydrogen Evolution Reaction, Feng-Ming Liu, Qi Han, Yan Xia Chen, Qi Ling Zhong, Bin Ren, Zhong Qun Tian

Journal of Electrochemistry

As one of the important mechanisms of SERS, the charge transfer (CT) enhancement requires the strong interaction of the adsorbed species with the substrate in order to permit the transition of charge between the metal Fermi level (energy state) and the molecular orbital [1] . The high enhancement needs the match of the energy gap between the Fermi level (or surface state) and the orbital energy level of the adsorbed molecules with the energy of the incident light. The electrode Fermi level is usually adjusted by the applied potential to satisfy the CT resonance. For the electrochemical reaction process, the …

Simple Relationships For The Estimation Of Melting Temperatures Of Homologous Series, James S. Chickos, Gary Nichols

James Chickos

No abstract provided.

Bacterial Residues In Coprolite Of Herbivorous Dinosaurs: Role Of Bacteria In Mineralization Of Feces, Thomas C. Hollocher, Karen Chin, Kurt T. Hollocher, Michael A. Kruge

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

The Cretaceous Two Medicine Formation of northwestern Montana has yielded blocky, calcareous coprolites that contain abundant fragments of conifer wood and were produced by large herbivorous dinosaurs. The coprolites are generally dark gray to black in color due to a dark substance confined chiefly within what originally were the capillaries of tracheid and ray cells of xylem. This substance is a kerogen which consists in part of thin-walled vesicles 0.1-1.3 µm in diameter. Pyrolysis products of this kerogen are diagnostic of a bacterial origin with a possible contribution from terrestrial plants. The vesicular component is interpreted as the residue of …

Preliminary X-Ray Diffraction Studies Of The Transcriptional Inhibitory Antibody Fab41.4, Johanna Mazlo, Robyn L. Stanfield, Ian A. Wilson, Steven H. Hinrichs, John J. Stezowski

Chemistry Department: Faculty Publications

The binding of transcription factor ATF-1 to DNA contributes to gene expression and regulation of cell growth. Antibody Mab41.4, raised against ATF-1, and its derivatives Fab41.4 and scFv41.4 inhibit specific DNA binding in vitro and induce apoptotic death of tumor cells in vivo. Structural studies of Fab41.4 were performed to gain insight into the mechanism of action of this potentially therapeutic antibody. The optimal conditions for crystallization of Fab41.4 were determined. Crystals were needle-like in appearance, displayed C2 space-group symmetry and diffracted to a resolution of 1.6 Å. The unit-cell parameters were determined to be a = 186.64, b = …

Development Of Amperometric Enzyme Electrodes For Glucose And Hypoxanthine., Eilish Broderick

Theses

This thesis is concerned with the immobilisation of enzymes on electrosynthesised poly (o- phenylenediamine) membranes for use on amperometric electrodes. The thesis opens with a discussion of the basic principles of enzymology and a review of a diverse range of biosensors, followed by a consideration of amperometry as governed by the Cottrell equation.

Glucose oxidase and horseradish peroxidase were co-immobilised in poly (o-phenylenediamine) on platinum electrodes at + 0.6 V versus Ag/AgCl. Using this approach the enzymes are entrapped in a strongly adherent, highly reproducible thin membrane, of thickness approximately 10 nm. This one-step procedure produces a glucose sensor with …

Production Of A Novel Copper-Binding Ligand By Marine Synechococcus (Cyanobacteria) In Response To Toxic Concentrations Of Copper, Arunsi C. Brown, Andrew S. Gordon

Virginia Journal of Science

Marine Synechococcus spp. are extremely sensitive to copper toxicity. Some strains have been shown to produce high-affinity, extracellular ligands of unknown structure which form complexes with free cupric ion. They are also known to produce metallothioneins (MT) in response to cadmium and zinc stress. In the present study, marine Synechococcus PCC 73109 (Agmenellum quadruplicatum BG-1) (Van Baalen) was exposed to three concentrations of CuSO₄ for various times. Size exclusion chromatography, atomic absorption spectrophotometry, and reverse phase HPLC were used to isolate an intracellular copper binding ligand of low molecular weight (< 6,500 Da). The ligand was detected after exposure to ≥ 8 μM CuSO₄ for 2 hr in BG-11 medium. …

Effects Of Humic Acids And Salinity On Pesticide Bioavailability And Toxicity As Estimated By Spme And Toxicity Tests, Laurent C. Mézin

Dissertations, Theses, and Masters Projects

The interactive effects of humic acids (HAs) and salinity on the bioavailability and toxicity of the pesticides chlorpyrifos and 4,4'-dichlorodiphenyltrichloroethane (DDT) were investigated. The effects of various HAs on the toxicity of chlorpyrifos were initially assessed with the chronic MicrotoxRTM test. Environmentally relevant concentrations of Aldrich, Peat, Leonardite and Suwannee River HAs had no significant effect on the toxicity of either chlorpyrifos or copper (Cu), the test's positive control. as reductions in contaminant toxicity had previously been reported for some contaminants by HAs, it appeared that salinity might be a mitigating factor. Thus salinity effects were further investigated with Aldrich …

Impedance Feedback Control For Scanning Electrochemical Microscopy, David O. Wipf, Mario A. Apuche-Avlles

College of Arts and Sciences Publications and Scholarship

A new constant-distance imaging method based on the relationship between tip impedance and tip-substrate separation has been developed for the scanning electrochemical microscope (SECM). The tip impedance is monitored by application of a high frequency ac voltage bias between the tip and auxiliary electrode. The high frequency ac current is easily separated from the dc level faradaic electrochemistry with a simple RC filter, which allows impedance measurements during feedback or generation/collection experiments. By employing a piezo-based feedback controller we are able to maintain the impedance at a constant value and, thus, maintain a constant tip-substrate separation. Application of the method …