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2002

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Articles 331 - 360 of 429

Full-Text Articles in Chemistry

Synthesis And Study Of New Materials For The Visual Detection Of Biomolecules, Ming He Jan 2002

Synthesis And Study Of New Materials For The Visual Detection Of Biomolecules, Ming He

LSU Doctoral Dissertations

The visual determination of saccharides has been of interest for well over a century. Sugars are a relatively challenging class of compounds to analyze. They exhibit great structural similarity as well as transparency in the visible region. The sensing of specific saccharides could aid the monitoring of disease or industrial fermentation products. Herein I present new methods allowing for simple and rapid visual detection of sialic acid, fructose and a homologous series of prototypical neutral oligosaccharides, the linear maltodextrins, containing up to seven glucose residues. The new methods allow for selective color detection of fructose in a large excess of …

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Poly(Methacrylic) Acid And \Gamma-Methacryloxypropyltrimethoxy Silane/Clay Nanocomposites Prepared By In-Situ Polymerization, Ahmet Gültek, Turgay Seçki̇n, Yunus Önal, M. Gali̇p İçduygu Jan 2002

Poly(Methacrylic) Acid And \Gamma-Methacryloxypropyltrimethoxy Silane/Clay Nanocomposites Prepared By In-Situ Polymerization, Ahmet Gültek, Turgay Seçki̇n, Yunus Önal, M. Gali̇p İçduygu

Turkish Journal of Chemistry

Poly(methacrylic acid) and poly(acrylic acid) nanocomposites were prepared by in-situ polymerization of \gamma-methacryloxypropyltrimethoxysilane (A174)/clay nanocomposites in which the macromonomer was generated by grafting A-174 onto activated clay samples via hydroxyl groups or via intercalation. In- situ polymerization was carried out in the presence of an initiator. It was found that the structural affinity between the methacrylic or acrylic acid monomers and the amount of clay played an important role in the hybrid structure. The nanocomposites were quantified by both X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and differential thermal analysis (DTA).

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The Membrane Potentials Of Periderm And Cuticular Membranes, Aygül Şahi̇n, Yunus Çengeloğlu, Mustafa Ersöz Jan 2002

The Membrane Potentials Of Periderm And Cuticular Membranes, Aygül Şahi̇n, Yunus Çengeloğlu, Mustafa Ersöz

Turkish Journal of Chemistry

The membrane potentials of periderm and cuticular membranes were measured with KCI and NaCl solution using Ag/AgCI electrodes. For the electromotive force (emf) measurements, the concentration in both compartments were brought to equilibrium with the 0.01 M concentration of KCI or NaCl solution, then the one side was kept constant and the other side changed. The estimation of the Donnan potential contribution to the membrane potential was carried out by taking into account the fixed charge concentration, C_x, value. From these measurements electrochemical characterization of the asymmetry and surface layers of the periderm and cuticular membranes can be described.

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The Role Of Size Exclusion Chromatography-Flame Atomic Absorption Spectrometry In The Treatment Chemistry Of Potable Water, Marina C. Koether Jan 2002

The Role Of Size Exclusion Chromatography-Flame Atomic Absorption Spectrometry In The Treatment Chemistry Of Potable Water, Marina C. Koether

Faculty Articles

The percentage composition of Al13, [AlO4Al12(OH)24(H2O)12]7+, in water treatment coagulants is an important criterion in the development and use of polymeric coagulants. Polymeric coagulants are generally used in cold climates or with highly turbid waters. Size exclusion chromatography–flame atomic absorption spectrometry (SEC-FAAS) can separate Al13 and monomeric Al within 6 min. The percentage composition of Al13 and monomeric Al is determined by solving two simultaneous equations. Due to overlapping peaks, a 10% error is associated with this method of quantification. This method can be …

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The Synthesis Of New Biotin Derivatives And Their Bioactivity, Latisha Chanette Johnson Jan 2002

The Synthesis Of New Biotin Derivatives And Their Bioactivity, Latisha Chanette Johnson

LSU Master's Theses

Biotin is an essential growth factor found in all living cells. It functions as a cofactor for a group of coenzymes that catalyze transcarboxylation, decarboxylation, and carboxylation reactions. Acetyl CoA carboxylase catalyzes the first committed and regulated step in fatty acid synthesis in which malonyl CoA is the product. The biotin-dependent enzyme is found in all animals, plants, and bacteria. We studied the kinetic and structural aspects of acetyl CoA carboxylase, and in 1999 we reported the bioactivity and total synthesis of a unique first generation biotin-derived inhibitor of acetyl CoA carboxylase, 1(BP1). Kinetic studies on the activity of E. …

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The Radiation-Induced Degradation Of Poly(Diene Sulfones) As X-Ray Resists, Gina Marie Calderon Jan 2002

The Radiation-Induced Degradation Of Poly(Diene Sulfones) As X-Ray Resists, Gina Marie Calderon

LSU Master's Theses

The microlithographic process, essential in the fabrication of silicon chip integrated circuits, uses high-energy radiation to transfer a pattern onto a thin film of polymer resist. Pattern transfer occurs by modifying the properties (solubility or volatility) of the polymer film exposed to radiation. Poly(olefin sulfones) exhibit a high sensitivity to x-rays, which is a desirable property for polymer resists, but typically undergo a glass transition around room temperature and a thermal degradation at moderate temperatures. The thermal properties of the poly(olefin sulfones) reduce the processing latitude for industrial microelectronics applications. Poly(unsaturated olefin sulfones) containing a carbon-carbon double bond in the …

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Analysis Of Plastics In The Tyre Industry Using Fourier Transform Infrared Techniques, Differential Scanning Calorimetry And Softening Point Apparatus, Ching Ching Loh Jan 2002

Analysis Of Plastics In The Tyre Industry Using Fourier Transform Infrared Techniques, Differential Scanning Calorimetry And Softening Point Apparatus, Ching Ching Loh

Student Works (2000-2009)

The plastics in a tyre factory were investigated. The plastics were analysed by FTlR-transmission, FTI.R-ATR, softening point apparatus as well as a Differential Scanning Calorimeter. All the plastics were detected to be polyethene based with melting point range of 107 to 125°C. It was also observed that The FTIR transmission spectrum can be different from the FTIR-ATR spectrum. The FTIR-ATR spectrum gives a higher band intensity at longer wavelengths compared to the FTIR-Transmission spectrum. Interference fringes can be present in the FTlR transmission spectrum. In addition to the above, it was also found that the melting point of plastics obtained …

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Solid Phase Extraction Of Pesticides With Determination By Gas Chromatography, Anwar A. Bhuiyan, Harry O. Brotherton Jan 2002

Solid Phase Extraction Of Pesticides With Determination By Gas Chromatography, Anwar A. Bhuiyan, Harry O. Brotherton

Journal of the Arkansas Academy of Science

A simple, rapid, and effective method for the extraction of fifteen organochlorine and organophosphorus pesticides based on the use of solid phase Bond Elut C-18 cartridges was studied as an alternative method to those based on extraction with organic solvents. Solid phase extraction is an attractive chromatographic sample preparation technology that reduces analysis time, costs, labor, and solvent consumption relative to traditional liquid/liquid extraction methods. The sample recoveries with the use of solid phase extractions were excellent for most pesticides. Analyte concentration by a factor as great as 1000-fold was achieved readily. The adsorbed pesticides were eluted from the solid …

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Alumina And Synthesis Intermediates Derived From Diethylkaluminum Amide, Benzaldehyde And Water, Stephen E. Hall, Lize Wilcox, William S. Tyree, David A. Lindquist, Malay K. Mazumder Jan 2002

Alumina And Synthesis Intermediates Derived From Diethylkaluminum Amide, Benzaldehyde And Water, Stephen E. Hall, Lize Wilcox, William S. Tyree, David A. Lindquist, Malay K. Mazumder

Journal of the Arkansas Academy of Science

The reaction of diethylaluminum amide [Et2AINH2] with benzaldehyde in toluene produces a solution of ethylaluminoxane polymer [EtAlO] and hydrobenzamide [PhCH=NCH(Ph)N=CHPh]. Alumina then is precipitated by the addition of water. Transition aluminas that may be useful in heterogeneous catalyst applications are obtained after calcining. Details of the chemistry of solution intermediates according to 1H NMR and the properties of the alumina product according to surface area analyses and powder x-ray diffraction are described.

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Modification Of Surface Properties Of Polymeric Materials, Rajesh Sharma, Robert A. Sims, Malay K. Mazumder Jan 2002

Modification Of Surface Properties Of Polymeric Materials, Rajesh Sharma, Robert A. Sims, Malay K. Mazumder

Journal of the Arkansas Academy of Science

Polymeric materials are successfully used in virtually all industries ranging from semiconductors, and coatings, to household appliances, automotive, and biomedical implants. Polymers generally have excellent bulk physical and chemical properties. However, certain properties of polymers such as low surface energy, low wettability, and high electrical resistivity sometimes limit their applications. Changing the bulk formulation of the polymers can alter some of these properties, but in general this is not acceptable as it can affect "desirable" bulk properties. Surface modification techniques have been used to alter polymer surfaces without affecting the bulk properties of the material. Most polymers have very high …

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Effect Of 6-Thioguanine And Methyl-6-Thioguanine On Stability Of Dna Duplexes, Mabaera Rodwell Jan 2002

Effect Of 6-Thioguanine And Methyl-6-Thioguanine On Stability Of Dna Duplexes, Mabaera Rodwell

Honors Theses

6-Thioguanine (65G) has been used for the past thirty years as an anti-cancer agent in maintenance chemotherapy for childhood acute lymphoblastic leukemia as well as acute myeloid leukemia. Despite its long-standing clinical use, little is understood of the molecular basis of the cytotoxicity associated with ?sG. Research has shown that ?sG is incorporated into DNA during replication after which it may exert its cytotoxicity by inducing rapid mutation or by affecting DNA-protein interactions. 65G has also been shown to impair HIV replication by inhibiting HlV-l reverse transcriptase and to inhibit human telomerase activity. To further understand the structural changes associated …

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Peroxynitrite-Mediated Oxidations: Nitration And Nitrosation, Rachel Bolzan Jan 2002

Peroxynitrite-Mediated Oxidations: Nitration And Nitrosation, Rachel Bolzan

LSU Doctoral Dissertations

Using a direct ultraviolet second-derivative spectroscopy method, three peroxynitrite preparative methods were investigated for the nitrite and nitrate present either as impurities or produced during peroxynitrite decomposition: (I) ozonation of azide, reaction of hydrogen peroxide with (II) isoamyl nitrite and (III) nitrous acid. The oxidation of morpholine by peroxynitrite in the presence and absence of added carbonate gives N-nitromorpholine and N-nitrosomorpholine. Nitration and nitrosation of morpholine are catalyzed by low levels of CO2; however, excess CO2 dramatically reduces the yields of nitrosation but not nitration, and the combined yields of the products are about the same under …

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Adsorptive Immobilization Of Cytochrome C On Indium/Tin Oxide (Ito): Electrochemical Evidence For Electron Transfer-Induced Conformational Changes, Asma El Kasmi, Michael C. Leopold, Ryan Galligan, Rebecca T. Robertson, S. Scott Saavedra, Kacem El Kacemi, Edmond F. Bowden Jan 2002

Adsorptive Immobilization Of Cytochrome C On Indium/Tin Oxide (Ito): Electrochemical Evidence For Electron Transfer-Induced Conformational Changes, Asma El Kasmi, Michael C. Leopold, Ryan Galligan, Rebecca T. Robertson, S. Scott Saavedra, Kacem El Kacemi, Edmond F. Bowden

Chemistry Faculty Publications

The adsorptive immobilization and electrochemistry of horse and yeast cytochrome c on indium/tin oxide (ITO) electrodes is reported. Near-monolayer coverage was achieved in pH 7 phosphate buffers of ionic strength equal to 10 and 50 mM, respectively, for the horse and yeast species. The layers exhibit very well-behaved voltammetry and are stable on the timescale of hours to days. Cyclic voltammetry revealed quasireversible behavior that is a product of both electron transfer (ET) kinetics and ET-induced conformational changes. A square scheme mechanism linking the redox states and the conformational states is proposed. Using a simple ET kinetic model that adequately …

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Formation Of Copper Dots In Copper Decoration Technique, Swee Yong Pung Jan 2002

Formation Of Copper Dots In Copper Decoration Technique, Swee Yong Pung

Student Works (2000-2009)

Copper ions are dissolved from highly pure copper plate into the methanol during copper decoration process. As a result, copper concentration in methanol is increased with time. The copper concentration in methanol measured by ICP-OES is correlated well with the calculated value based on the magnitude of current and time during the process. Consequently, higher magnitude of current can be applied to build up copper concentration in methanol in shorter period. When copper ions are ejected in methanol, they are positively charged. They experience force from electric field and migrate towards oxide surface. Eventually, these copper ions will be discharged …

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Spectrophotometric Determination Of Mexiletine Hydrochloride In Capsules Using Bromothymol Blue, Zeynep Aydoğmuş, S. Müge Çeti̇n, Sedat Tosunoğlu Jan 2002

Spectrophotometric Determination Of Mexiletine Hydrochloride In Capsules Using Bromothymol Blue, Zeynep Aydoğmuş, S. Müge Çeti̇n, Sedat Tosunoğlu

Turkish Journal of Chemistry

A new spectrophotometric method based on the formation of an ion-pair using bromothymol blue as ion-pair complexing reagent was developed for the determination of mexiletine hydrochloride in capsules. The ion-pair formed was highly coloured and easily extracted with dichloromethane. The calibration curve was linear over the concentration range 1.08--10.8 \mu g.ml^{-1} at \lambda_{max} = 408 nm (r = 0.9999). The results obtained from the developed method were compared statistically with those obtained by the British Pharmacopeia method.

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Trace Element Accumulation In Selected Bioindicators Exposed To Emissions Along The Industrial Facilities Of Danube Lowland, Heide Spiegel Jan 2002

Trace Element Accumulation In Selected Bioindicators Exposed To Emissions Along The Industrial Facilities Of Danube Lowland, Heide Spiegel

Turkish Journal of Chemistry

The scope of this study was to investigate the effects of the atmospheric emissions of two significant industrial centres of the Danube Lowland: the Schwechat and Slovnaft refineries. In this connection the environmental pollution of emission zones by heavy metals on the base of selected bioindicators (soil, lucerne, wheat, earthworms) should be evaluated. The phenomenon of the atmospheric impact of heavy metal aerosols on the food chain and substance transfer for the model studied (soil - plants - terrestrial invertebrates) was quantified by transfer (bioaccumulation) factors. Due to the orographic depression between the Eastern Alps and Western Carpathian Mountains and …

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Swelling Of Superabsorbent Acrylamide/Sodium Acrylate Hydrogels Prepared Using Multifunctional Crosslinkers, Erdener Karadağ, Dursun Saraydin Jan 2002

Swelling Of Superabsorbent Acrylamide/Sodium Acrylate Hydrogels Prepared Using Multifunctional Crosslinkers, Erdener Karadağ, Dursun Saraydin

Turkish Journal of Chemistry

Superwaterabsorbent acrylamide-sodium acrylate hydrogels were Prepared by free radical polymerization in aqueous solutions of acrylamide and of acrylamide with sodium acrylate as comonomer. For each copolymerization, nine different compositions were used and in all systems a concentration of a multifunctional crosslinker such as trimethylolpropane triacrylate, ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate and N,N'-methylenebisacrylamide was employed. As a result of dynamic swelling tests, the influence of crosslinkers and the relative content of sodium acrylate on the swelling properties, the initial swelling rate and the swelling rate constant, swelling exponent, swelling coefficients and diffusional behaviour of water in the hydrogel systems were examined. …

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Anodic Behavior Of Tungsten In H_{3}Po_{4}-K_{2}So_{4}-H_{2}So_{4}/Koh Solutions, Mustafa Anik Jan 2002

Anodic Behavior Of Tungsten In H_{3}Po_{4}-K_{2}So_{4}-H_{2}So_{4}/Koh Solutions, Mustafa Anik

Turkish Journal of Chemistry

Potentiodynamic and potentiostatic polarizations were used to study the effect of pH on the anodic reaction characteristics of tungsten (W) in a very broad pH range (0.4-13). The open circuit potential was observed to decrease with a constant slope of 58 mV/pH, as pH increased. The oxide phase of W showed typical amphoteric surface behavior in the acidic regime. The oxide dissolution went through a minimum at pH 2.5, which was identified as the point of zero charge (pzc) of W--oxide. The oxide dissolution below the pzc was H^{+} -assisted and above the pzc was OH^{-}-assisted. At around the pzc …

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Determination Of Cadmium By Faas After Solid-Phase Extraction Of Its 1-Benzylpiperazinedithiocarbamate Complex On Microcrystalline Naphthalene, Hasan Cesur, Beki̇r Bati Jan 2002

Determination Of Cadmium By Faas After Solid-Phase Extraction Of Its 1-Benzylpiperazinedithiocarbamate Complex On Microcrystalline Naphthalene, Hasan Cesur, Beki̇r Bati

Turkish Journal of Chemistry

By using 1-benzylpiperazinedithiocarbamate (1-BPzDC) as a new reagent, a method of solid-phase extraction is described for the pre-concentration of cadmium in water samples prior to its determination by flame atomic absorption spectrometry (FAAS). This method is based on the fact that cadmium forming in aqueous phase cadmium 1-benzylpiperazinedithiocarbamate complex (Cd(1-BPzDC)_{2}) can be extracted with microcrystalline naphthalene on solid phase, then back-extracted with potassium cyanide solution into aqueous phase and measured by FAAS. The optimum experimental parameters for the extraction and back-extraction of cadmium were investigated. The obtained recovery was nearly 97% when the enrichment factor was 500 for spiked cadmium …

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Determination Of The Protonation Constants Of Some Substituted Salicylideneanilines By The Spectrophotometric Method In Ethanol-Water Mixtures, M. Abdülkadi̇r Akay, Esi̇n Canel, Esma Kiliç, Fi̇tnat Köseoğlu Jan 2002

Determination Of The Protonation Constants Of Some Substituted Salicylideneanilines By The Spectrophotometric Method In Ethanol-Water Mixtures, M. Abdülkadi̇r Akay, Esi̇n Canel, Esma Kiliç, Fi̇tnat Köseoğlu

Turkish Journal of Chemistry

Protonation constants of salicylideneaniline and methyl-, ethyl-, methoxy- fluoro-, chloro-, bromo- and iodo- substituted salicylideneanilines were determined by spectrophotomeric titrimetry in 10, 30, 50 and 70% ethanol-water mixtures at constant ionic strength and at 25^{o}C. The results obtained from this work were compared with those obtained using the potentimetric method. The difference between the results found with these two methods was approximately \pm $ 0.20 logK units. The spectrophotometric method was judged to be more suitable than the potentiometric method for halogen substituted salicylideneanilines with the low logK values and in the solvent mixture containing 10% ethanol, due to the …

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Determination Of Manganese And Iron In Magmatic Rocks After Ultrasonic Leaching By Flame Aas, M. Hi̇kmet Özkan, Mehmet Akçay Jan 2002

Determination Of Manganese And Iron In Magmatic Rocks After Ultrasonic Leaching By Flame Aas, M. Hi̇kmet Özkan, Mehmet Akçay

Turkish Journal of Chemistry

An alternative sample preparation method has been developed for destructive analysis of magmatic rock sample. The method simply included the crushing, HF treatment and 1% HCl leaching steps of the rock samples under ultrasonic effects. There is no need to exhaust all of the sample through the operation. A reproducible and representative, partial recovery of an analyte was expected in a procedural sequences consisting of strictly defined steps. The changes in analyte recoveries were investigated by sample grain size, sample mass, applied ultrasonic power and sonication time. The optimum recovery conditions were examined. In addition, the kinetics of the dissolution …

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A New Synthesis Of Bromobenzotropones: Oxidation Of 8-Bromo-5 H -Benzo[A]Cycloheptene, Ari̇f Daştan, Y. Kemal Yildiz, Cavi̇t Kazaz, Meti̇n Balci Jan 2002

A New Synthesis Of Bromobenzotropones: Oxidation Of 8-Bromo-5 H -Benzo[A]Cycloheptene, Ari̇f Daştan, Y. Kemal Yildiz, Cavi̇t Kazaz, Meti̇n Balci

Turkish Journal of Chemistry

The oxidation of 8-bromo-5H-benzo[a]cycloheptene with some oxidation reagents was studied. 2,3- and 4,5-benzotropone derivatives were obtained. The structures of the bromobenzotropones were determined by ^{1}H- and ^{13}C-NMR data.

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Synthesis And Electronic Structure Of New Aryl- And Alkyl-Substituted 1,3,4-Oxadiazole-2-Thione Derivatives, Feray Aydoğan, Zuhal Turgut, Nüket Öcal, Safi̇ye Sağ Erdem Jan 2002

Synthesis And Electronic Structure Of New Aryl- And Alkyl-Substituted 1,3,4-Oxadiazole-2-Thione Derivatives, Feray Aydoğan, Zuhal Turgut, Nüket Öcal, Safi̇ye Sağ Erdem

Turkish Journal of Chemistry

New 5-alkyl and 3-(2,4-dimethylphenyl) substituted 1,3,4-oxadiazole-2-thione derivatives were synthesized by the ring closure reactions of various acylhydrazides with carbon disulphide. Mannich bases for some of these compounds were also synthesized by condensation with benzaldehyde and primary amines. All new compounds were characterized by spectral data. Most of them were tested for their antibacterial and antituberculostatic activity. Molecular orbital calculations at the HF/6-31G** level were also performed to determine the optimized geometrical structures. Results indicated electron delocalization over several atoms of the ring. An additional study on the tautomeric equilibrium between 1,3,4-oxadiazole-2-thione and its thiol form showed that the thione tautomer …

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Determination Of Trace Elements In Iron Minerals By Atomic Absorption Spectrometry, Trajce Stafilov, Dragica Zendelovska Jan 2002

Determination Of Trace Elements In Iron Minerals By Atomic Absorption Spectrometry, Trajce Stafilov, Dragica Zendelovska

Turkish Journal of Chemistry

A method for the determination of lead, cobalt, nickel, chromium, zinc and manganese in iron minerals siderite (FeCO_3), hematite (Fe_{2}O_{3), pyrite and marcasite (FeS_{2) by flame and Zeeman electrothermal atomic absorption spectrometry (ETAAS) was developed. Interferences were investigated by measuring the absorbance of the elements investigated in series of samples with varying mass ratios of the elements investigated and iron as the potential interfering element. It was found that there was no interference in the determined mass ratios of iron on the absorbance of Mn and Zn and that they could be directly analyzed by flame and electrothermal atomic absorption …

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Derivative Spectrophotometric Determination Of Caffeine In Some Beverages, Güzi̇n Alpdoğan, Kadi̇r Karabi̇na, Sidika Sungur Jan 2002

Derivative Spectrophotometric Determination Of Caffeine In Some Beverages, Güzi̇n Alpdoğan, Kadi̇r Karabi̇na, Sidika Sungur

Turkish Journal of Chemistry

Caffeine content was determined in cola, coffee and tea by second and third order derivative spectrophotometry without using any separation or background correction technique and reagent. The method is based on the measurement of the distances between two extremum values (peak to peak amplitudes) in the second order (cola) and third order (coffee and tea) derivative spectra of the sample solution. Calibration curves were constructed for the 2.0-10.0 \mu g ml^{-1}concentration range. As a reference method, reversed phase high performance liquid chromatographic procedure was developed. Commercially available beverages were analyzed by the two methods and the results were statistically compared …

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A Semi-Empirical Study On Metal Ion/Murexide Complexation, N. Zeynep Atay, Tereza Varnali Jan 2002

A Semi-Empirical Study On Metal Ion/Murexide Complexation, N. Zeynep Atay, Tereza Varnali

Turkish Journal of Chemistry

Modeling of the metal ion/ligand complexation reactions between divalent metal cations (M^{2 +} ) and hydrophilic tridentate ligand murexide (Mu^{-} ) in water, water+glycerol, and in glycerol was carried out. Kinetic studies showed that the rate of the reaction is very dependent on the metal ion, with Zn^{2 +} > Ni^{2 +} , but, reactions are slower in dispersed glycerol than in dispersed water. Theoretical calculations, which have shown a metal ion dependence, were consistent with the experimental observations. The entropy values calculated in all solvents were negative and were similar in value, indicating that these spontaneous reactions are enthalpy driven.

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The Effect Of Acid Activation On Some Physicochemical Properties Of A Bentonite, Müşerref Önal, Yüksel Sarikaya, Tülay Alemdaroğlu, İhsan Bozdoğan Jan 2002

The Effect Of Acid Activation On Some Physicochemical Properties Of A Bentonite, Müşerref Önal, Yüksel Sarikaya, Tülay Alemdaroğlu, İhsan Bozdoğan

Turkish Journal of Chemistry

A white calcium bentonite (CaB) from the K\"{u}tahya region/Turkey was activated by heating it for 6 hours at 97°C in H_{2}SO_{4} solution. The mass percentage of H_{2}SO_{4} in the bentonite-acid mixture was varied from 0 to 70%. The chemical analysis (CA), cation exchange capacity (CEC), differential thermal analysis (DTA) curves and X-ray diffraction (XRD) patterns of the prepared samples were determined. The specific surface area (A) and the specific micropore-mesopore volume (V) were calculated respectively from the adsorption and desorption data of N_{2} obtained at liquid N_{2} temperature. How the calcium montmorillonite (CaM) layers in the CaB were decomposed during …

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Production Of Mesophase Pitch From Coal Tar And Petroleum Pitches Using Supercritical Fluid Extraction, Mustafa Zafer Özel, Keith D. Bartle Jan 2002

Production Of Mesophase Pitch From Coal Tar And Petroleum Pitches Using Supercritical Fluid Extraction, Mustafa Zafer Özel, Keith D. Bartle

Turkish Journal of Chemistry

Supercritical fluid extraction (SFE) is currently being investigated as a possible technique in the production of high quality mesophase pitch from coal tar and petroleum pitches. Mesophase pitch is used to make high technology products, such as carbon fibre. The conventional production of mesophase pitch initially involves the removal of low molecular weight species from coal tar and petroleum pitches. The remaining residue is then transformed into a mesophase pitch through a polymerisation process. The aim of this study involves the extraction of light molecular weight species using SFE. Both petroleum and coal tar pitch contain complex aromatic molecules with …

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Electrochemical Investigation Of 4'-Haloderivatives Of N,N-Dimethyl-4-Aminoazobenzene, Mustafa Uçar, Ali̇ Osman Solak, M. Levent Aksu, Mehmet Toy Jan 2002

Electrochemical Investigation Of 4'-Haloderivatives Of N,N-Dimethyl-4-Aminoazobenzene, Mustafa Uçar, Ali̇ Osman Solak, M. Levent Aksu, Mehmet Toy

Turkish Journal of Chemistry

In this study, the electrochemical behaviour of 4' -halogene-N,N-dimethyl-4-aminoazobenzene derivatives were investigated using various polarographic and voltammetric methods. The peak potentials of these derivatives were observed to shift towards negative values with increase in pH. The standard rate constants were determined with (Laviron technique) or without (Nicholson and Klingler-Kochi techniques) taking the adsorption phenomena into account. The diffusion coefficients were calculated from the cyclic voltammetric data using the method developed by Garrido. The amount of adsorbed substances (surface excess values) and transfer coefficients for the electron transfer were also determined. These compounds can be quantitatively determined between 1 x 10^{-5} …

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Trypsin-Catalyzed Peptide Synthesis In Acetonitrile With Low Water Content, Yeşi̇m Yeşi̇loğlu, Ayten Sağiroğlu Jan 2002

Trypsin-Catalyzed Peptide Synthesis In Acetonitrile With Low Water Content, Yeşi̇m Yeşi̇loğlu, Ayten Sağiroğlu

Turkish Journal of Chemistry

Trypsin was immobilized to alumina by adsorption from its aqueous solutions. The activity of trypsin was increased by immobilization for peptide synthesis. With these immobilized enzymes Bz-Arg-Leu-NH_{2} dipeptide synthesis was carried out. Iso amylalcohol, tetrahydrofuran and acetonitrile were used as solvents giving the highest yield in the peptide formation reaction. The yield of the peptide was strongly dependent on water content in the reaction medium. The stability of alumina-immobilized trypsin is described.

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