• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 245
  • 202
  • 42
  • 42
  • 26
  • 18
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 629
  • 629
  • 200
  • 195
  • 127
  • 122
  • 110
  • 100
  • 99
  • 98
  • 72
  • 66
  • 61
  • 59
  • 56
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Water-based headspace single-drop microextraction and capillary electrophoresis for the determination of volatile inorganic compounds in complex matrices / Mikroekstrakcija iš viršerdvės vandens lašu – kapiliarinė eleroforezė lakių neorganinių junginių nustatymui sudėtingose ktmatricose

Nabiyeva, Svetlana 14 December 2010 (has links)
The objective of the present work was systematic investigation of water-based headspace single-drop microextraction (SDME) technique, its conjunction with capillary electrophoresis, and application for the analysis of volatile inorganic compounds (cyanide and ammonium) in biomedical and environmental samples. Theoretically evaluated and experimentally confirmed that the manipulation in the volatility of the analyte by its chemical modification in the sample and/or in the acceptor phase is the most effective way to enhance the extraction performance in headspace SDME. Maximum extraction efficiency for cyanide was observed in the pH range 4.5–7.5, where cyanide anion is completely transferred into volatile HCN. Complete cyanide recoveries (≥96%) from metal-cyanide complexes were obtained by using two ligand-exchange reagents (ethylenediamine and dithizone). Maximum extraction efficiency was observed by the extraction of ammonia from alkaline samples (pH≥11) with neutral or slightly acidic acceptor phase (pH 3-7). Compared to existing methods water-based headspace SDME is significantly faster and simpler. In addition, proposed technique does not require any sample pre-treatment (deproteinization, acidic/alkaline distillation, etc.) and thus is much less susceptible to interferences. Finally, it offers possibility to choice of a wider variety of solvents and, consequently, enhances the range of extractable analytes as well as the range of analytical methods that can be coupled... [to full text] / Daktaro disertacijoje nuodugniai ištirtas mikroekstrakcijos iš viršerdvės vandens lašu metodas, apjungtas su kapiliarine elektroforeze bei pritaikytas lakių neorganinių junginių (cianido ir amonio) koncentravimui ir nustatymui biomedicininiuose ir aplinkos objektuose. Teoriniais skaičiavimais parodyta ir eksperimentiškai patvirtinta, kad efektyviausias būdas mikroekstrakcijos iš viršerdvės efektyvumui pagerinti – analitės lakumo didinimas chemiškai modifikuojant ją prieš ekstrakciją ir/arba jos lakumo mažinimas modifikuojant ją akceptorinėje fazėje. Maksimalus cianido mikroekstrakcijos efektyvumas pasiekiamas pH srityje 4,5- 7,5, kur cianidas kiekybiškai pervedamas į lakų HCN. Ištyrus cianido mikroekstrakciją tirpiklio lašu iš metalų cianidinių kompleksų tirpalų nustatyta, kad kiekybiškas silpnai surišto cianido suardymas (cianido išgavos siekia ≥96%) pasiekiamas panaudojus ligandų mainus etilendiamino ir ditizono mišiniu. Maksimalus amonio mikroekstrakcijos efektyvumas pasiekiamas ekstrahuojant jį iš pašarmintų mėginių (pH≥11) akceptorine faze, kurios pH 3-7. Lyginant su standartiniais metodais, siūlomas metodas yra greitesnis ir paprastesnis, visiškai eliminuojama mėginio matricos įtaka, nereikalingos jokios drastiškos (deproteinizacija, veikimas rūgštimis/šarmais, distiliacija ir pan.) manipuliacijos su mėginiu, todėl išvengiama mėginio matricos įtakos. Mikroekstrakcija iš viršerdvės vandens lašu praplečia mikroekstrakcijos metodų taikymo sritis: atveriama galimybė labai... [toliau žr. visą tekstą]
252

Scalable, modular, integrated genetic analysis systems

Bidulock, Allison Christel Elizabeth Unknown Date
No description available.
253

Signal processing and amplifier design for inexpensive genetic analysis instruments

Choi, Sheng Heng Unknown Date
No description available.
254

APPLICATIONS OF GAS CHROMATOGRAPHY/MASS SPECTROMETRY AND CAPILLARY ELECTROPHORESIS FOR THE ANALYSIS OF LIGNOCELLULOSIC BIOMASS PRETREATMENT

Kato, Dawn M 01 January 2014 (has links)
The focus of this dissertation centers on the development and applications of gas chromatography/mass spectrometry and capillary electrophoresis methodologies to quantify monomeric compositions of the β-O-4 linkages in lignin. Pretreatment is a required step in the utilization of lignocellulosic biomass for biofuels. Lignin is the target of pretreatment because it hinders the accessibility of enzymes and chemicals to cellulose. The effects of pretreatment are commonly assessed utilizing enzymatic saccharification and lignin assays. However, these techniques do not elucidate the effects of pretreatment on the monomeric make up of lignin. The overarching hypothesis of this dissertation is that changes in individual monolignol content upon pretreatment can be observed from quantification. To test the hypothesis, a pretreatment, solution phase Fenton chemistry, was conducted on various lignocellulosic biomass feedstocks. Enzymatic saccharification studies showed a significant increase in glucose production upon Fenton pretreatment, however, lignin assays did not show a significant decrease in lignin content. Project two of this dissertation aimed to synthesize analytical standards in order to develop a quantitative thioacidolysis technique. The successful synthesis of the three arylglycerols were conducted utilizing and epoxidation reaction scheme which was hypothesized to produce a single diastereomer, as supported by GC/MS and chiral CE analysis. Upon method development, a quantitative thioacidolysis GC/MS method was applied to untreated and Fenton treated biomass. Results from this project revealed there was no significant change in the three lignin monomers. To verify the method, quantitative thioacidolysis GC/MS method was applied to a pretreatment method known to degrade lignin, alkaline peroxide pretreatment. The results of this project showed a significant change in monolignol concentrations upon alkaline peroxide pretreatment. Analytical degradative techniques, such as thioacidolysis, has traditionally assessed lignin as monomeric ratios. However, as this dissertation showed, upon alkaline peroxide pretreatment, no significant change was seen in the monomeric ratios, but there was a significant difference in all three monolignol concentrations. These results support the overall hypothesis that changes in individual monolignol content upon pretreatment can be observed from quantification. The works of this dissertation provides an analytical method which contributes to the elucidation of lignin.
255

Development of a capillary electrophoretic method for the separation and detection of resin acids

Rigby, Tracey. January 2000 (has links)
A method for the separation and detection of standard resin acids (RAs), commonly found in pulp mill effluent and known to bioaccumulate in fish bile, was optimized using cyclodextrin modified electrokinetic capillary electrophoresis (CD-EKC) with ultra violet (UV) and laser induced fluorescence (LIF) detection. Optimal separation conditions were found with RA standards using UV detection at 214 nm, with a 72 mM sodium borate buffer pH 9.25, containing 35 mM beta-cyclodextrin sulfobutyl ether (SPCD), 15 mM of methyl-beta-cyclodextrin (MECD) and a 37 cm capillary with an internal diameter of 50pm. This resulted in a 12-min separation and the identification of 9 peaks, with a LOD of 10 ppm. To enable increased sensitivity, RAs were derivatized using the fluorescent label 4-BrMMc. A method for extracting resin acids from spiked fish bile and pulp mill effluent was developed, the extracted samples were derivatized, separated and identified using CD-EKC with LIF detection. The method of extraction and derivatization using CD-EKC was applied to biological samples of contaminated effluent and fish bile. (Abstract shortened by UMI.)
256

Enhancement of sensitivity in capillary electrophoresis : forensic and pharmaceutical applications /

Al Najjar, Ahmed Omer. January 2004 (has links)
Thesis (Ph.D.)--Ohio University, November, 2004. / Includes bibliographical references (p. 163-171)
257

Capillary electrophoresis, high resolution inductively coupled plasma mass spectrometry elemental speciation and applications in pharmaceutical process research.

Bu, Xiaodong, January 2007 (has links)
Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Chemistry and Chemical Biology." Includes bibliographical references (p. 269-270).
258

Investigation of the Barrett's esophagus cell line by capillary electrophoresis /

Jones, Megan Renee. January 2006 (has links)
Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 159-174).
259

Application of CE, HPLC and LC-MS-MS for the analysis and quality control of Ginkgo biloba dosage forms /

Dubber, Mary-Jean. January 2005 (has links)
Thesis (Ph. D. (Pharmacy))--Rhodes University, 2006.
260

Enhancement of sensitivity in capillary electrophoresis forensic and pharmaceutical applications /

Al Najjar, Ahmed Omer. January 2004 (has links)
Thesis (Ph.D.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (p. 163-171)

Page generated in 0.0362 seconds