Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 73-75). Also available via the Internet.

by Kwan Hok-wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 67-69). / Abstracts in English and Chinese. / Acknowledgment --- p.i / Abstract --- p.ii / Chapter 1. --- INTRODUCTION / Chapter 1.1 --- Chemical speciation of cyanide --- p.1 / Chapter 1.2 --- Review of analytical techniques for cyanide determination --- p.3 / Chapter 1.3 --- Importance of sediment in the environment --- p.6 / Chapter 1.4 --- Characteristics of marine sediment --- p.6 / Chapter 1.5 --- Antropogenic sources of cyanide --- p.7 / Chapter 1.6 --- Research objective --- p.8 / Chapter 1.7 --- Brief description of the project --- p.9 / Chapter 2. --- INSTRUMENTATION AND THEORY / Chapter 2.1 --- Instrumentation for flow injection analysis system --- p.11 / Chapter 2.2 --- Basic principles of flow injection analysis --- p.21 / Chapter 2.3 --- Basic principles of amperometric detection --- p.24 / Chapter 3. --- EXPERIMENTAL / Chapter 3.1 --- Instrumentation --- p.25 / Chapter 3.2 --- Reagents --- p.32 / Chapter 3.3 --- Sample preparation --- p.34 / Chapter 4. --- RESULTS AND DISCUSSION / Chapter 4.1 --- Effect of bismuth on on-line precipitation of sulphide in FIA --- p.37 / Chapter 4.2 --- Calibration --- p.37 / Chapter 4.3 --- Effectiveness of the distillation conditions --- p.41 / Chapter 4.4 --- Comparisons of cyanide extraction methods for sediment analysis --- p.42 / Chapter 4.5 --- Effect of bismuth nitrate on cyanide recoveries --- p.45 / Chapter 4.6 --- Effect of bismuth nitrate on cyanide recoveries in the presence of sulphide --- p.48 / Chapter 4.7 --- Effect of bismuth nitrate on recoveries of total cyanide in the analysis of interlaboratory test samples --- p.55 / Chapter 4.8 --- Recoveries of complexed cyanide in the analysis of SETOC sample with sulphide interference --- p.57 / Chapter 4.9 --- Analysis of marine sediment samples --- p.58 / Chapter 4.10 --- Recovery tests and precision studies --- p.59 / Chapter 4.11 --- Interferences --- p.62 / Chapter 5. --- CONCLUSION --- p.66 / Chapter 6. --- REFERENCES --- p.67

No description available.

No description available.

Thesis (M.S.)--Youngstown State University, 1995. / Includes bibliographical references (leaves 69-71).

A sodium fusion-Ion chromatographic method for determination of fluorine, chlorine, bromine, and iodine in organic compounds is described. Seventeen organic halogen compounds and eleven mixtures were decomposed by Na fumes at 280-290°C for one hour or longer. The absorbing solutions were injected for ion chromatographic analysis using electrochemical and conductometric detectors. The arrangement of the apparatus includes the placement of the electrochemical and conductometric detectors. This method provides a mechanism providing for complete analysis for all four halogens in one ion chromatographic sample injection. Reproducibility is excellent and liquid sample handling is mentioned.

by Chuen-shing Mok. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 192-193). / Chapter Chapter 1 --- INTRODUCTION --- p.1 / Chapter Chapter 2 --- INSTRUMENTATION AND THEORY --- p.9 / Chapter Chapter 3 --- INDIRECT CONDUCTOMETRIC DETECTION OF AMINO ACIDS AFTER HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC SEPARATION --- p.17 / Chapter Chapter 4 --- DETERMINATION OF MONOSODIUM GLUTAMATE IN FOODS WITH HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY USING INDIRECT CONDUCTOMETRIC DETECTION --- p.52 / Chapter Chapter 5 --- HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC DETERMINATION OF ACTIVE INGREDIENTS IN COUGH-COLD SYRUPS WITH INDIRECT CONDUCTOMETRIC DETECTION --- p.83 / Chapter Chapter 6 --- HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC DETERMINATION OF ATROPINE AND ATROPINE- LIKE ALKALOIDS IN PHARMACEUTICAL PREPARATIONS WITH INDIRECT CONDUCTOMETRIC DETECTION --- p.144 / Chapter Chapter 7 --- CONCLUSION --- p.194

M.S.

Este trabalho descreve o desenvolvimento de um biossensor contendo transdução condutométrica sem contato (C4D, capacitively coupled contactless conductivity detection) e ácido fólico (FA) como biorreceptor em microchip, uma nova alternativa que poderá ser utilizada na determinação do biomarcador tumoral FR-α. Essa espécie exibe interações com FA altamente específicas, com constantes de formação da ordem de 109-1010. Os dispositivos microfluídicos, os quais consistiram de uma lâmina de vidro (integrando os eletrodos), dielétrico (contendo a fase biossensora) e substrato de poli(dimetilsiloxano) (PDMS, incorporando os microcanais), foram fabricados utilizando-se processos de fotolitografia e deposição de filmes finos em fase vapor. Objetivando melhorias nos níveis de detecção da C4D, estudos de sensibilidade com base em parâmetros da curva analítica foram conduzidos alterando-se a natureza do dielétrico e a configuração dos eletrodos. Posteriormente, estudos de caracterização foram realizados para as superfícies modificadas com os intermediários de imobilização; condições reacionais distintas (reagente, concentração, solvente e tempo) foram consideradas. As técnicas de microscopia eletrônica de varredura e espectroscopia de fotoelétrons excitados por raios-X foram usadas, respectivamente, a fim de se verificar a possível formação de aglomerados e permitir determinações qualitativas e quantitativas sobre as composições químicas das superfícies. Como resultado dos experimentos de sensibilidade e caracterização de superfície, adotamos os parâmetros seguintes para os ensaios de interações biomoleculares posteriores: filme de SiO2 como dielétrico, eletrodos seletivos à C4D com formato retangular e orientação antiparalela e monocamadas automontadas do reagente 3-aminopropil(trietoxisilano) como intermediário de imobilização de FA. As duas etapas finais do trabalho foram: otimização do tempo de funcionalização com FA (3, 5 e 7 h) e caracterização da fase biossensora, realizada a partir de medidas de C4D e microscopia de força atômica (AFM). Para o primeiro caso, os microchips foram aplicados a um padrão de anticorpo monoclonal específico a FA (α-FA). Os ensaios biomoleculares indicaram uma adsorção efetiva de FA junto à superfície de SiO2 silanizada, sem a ocorrência (ao menos em níveis significativos) de impedimentos estéricos de sua espécie bioativa. Dentre os tempos de funcionalização investigados, 3 h foi aquele que resultou em uma maior sensibilidade do método. Em termos da etapa de caracterização eletroquímica da fase biossensora, seus resultados mostraram haver correlação entre a resposta analítica e as interações FA/α-FA. Em adição, conforme indicaram as medidas de AFM, não houve alterações drásticas na morfologia do substrato (SiO2) em função dos processos de modificação química de superfície. Por fim, o uso da C4D como uma técnica de transdução em biossensores mostrou-se uma alternativa promissora para a análise do biomarcador tumoral FR-α. Dentre outros aspectos, essa plataforma analítica requer uma instrumentação simples, barata e portátil, não apresenta inconvenientes relacionados ao contato eletrodo/solução, dispensa o uso de mediadores redox e permite a determinação simultânea de multianalitos. Neste ínterim, alterações no transdutor devem ser implementadas visando um aumento na sensibilidade do método, o qual representa seu fator limitante principal. / This work describes the development of a biosensor containing capacitively coupled contactless conductivity transduction (C4D) and folic acid (FA) as bioreceptor in microchip, a new alternative that can be used in FR-α tumor biomarker analysis. FR-α exhibits highly specific interactions with FA, showing formation constants of the order of 109-1010. The microfluidic devices consisted of a glass layer (integrating the electrodes), dielectric (containing the biosensor phase), and poly(dimetilsiloxane) substrate (PDMS, incorporating microchannel). The microfabrication stage evolved photolithography processes, metal adsorption via sputtering, and plasma-enhanced vapor film deposition. In order to improve detection levels of C4D, sensitivity studies were conducted by changing the dielectric nature and electrode configuration. Through flow analysis with given electrolyte standards, the limits of detection and quantification were calculated based on analytical curve parameters. Subsequently, researches were performed to characterize the modified surfaces with immobilization intermediate considering reaction conditions distinct (reagent, concentration, solvent, and time). The techniques of scanning electron microscopy and X-ray photoelectron spectroscopy were employed, respectively, aiming to verify the clusters formation and allow qualitative and quantitative determinations about the surfaces chemical composition. From the results of sensitivity experiments and surface characterization, we adopt the following parameters for the biomolecular interactions assays: SiO2 film as dielectric, C4D selective electrodes with rectangular shape and antiparallel orientation, and self-assembled monolayers of 3-aminopropyl(triethoxysilane) as intermediary for immobilization of FA. The two final steps of the work were: optimizing the FA functionalization time (3, 5, and 7 h) and phase biosensor characterization, made from measures of C4D and atomic force microscopy (AFM). For the first case, due to the absence of FR-α standard for purchase, the microchips were applied to FA specific monoclonal antibody (α-FA). The biomolecular assay indicated effective adsorption of FA, without occurrence (at least in significant levels) of steric hindrance of its bioactive specie. Among the investigated times of functionalization, 3 h resulted in a higher sensitivity of the method. In terms of biosensor phase electrochemical characterization stage, their results evidenced correlation between analytical response and FA/α-FA interactions. Additionally, as the AFM measurements showed, drastic changes in the morphology of the substrate (SiO2) with the surface modification processes did not occur. Finally, the use of the C4D as transduction technical in biosensors proved to be a promissory alternative for FR-α tumor biomarker analysis. Among other features, this platform has not drawbacks related to the electrode/solution contact, dispenses the use of redox mediators, allows the simultaneous determination of multianalytes, and employs an instrumentation that is simple, cheap, and portable. Nevertheless, changes in the transducer should be implemented to increase the method sensitivity, which represents its main limiting factor.

Zeolites are crystalline aluminosilicates which have highly ordered pore structures and high surface area. Also the tailorable surface properties, high ion-exchange capability, high chemical, thermal, and mechanical strength make these particles an important candidate for various application such as sensors, catalysis, dielectric materials, separation, and membrane technologies. Although zeolites have these unique properties, applications where zeolites are integrated into devices according to their application areas, are limited due to the powder form of the material. The purpose of the current study was to investigate the effect of zeolite nanoparticles on conductometric biosensor performance and cell viability measurements. Firstly, zeolite attachment on silicon surfaces was investigated by attaching silicalite and zeolite A nanoparticles onto the silicon substrates by direct attachment methodology in a closely packed monolayer form with perfect orientation and full coverage without using any chemical linker. Furthermore, the ability to pattern these zeolite crystals on silicon substrates with electron beam lithography and photolithography techniques was investigated. With the combination of electron beam lithography and direct attachment methodology, zeolite patterns were produced with feature sizes as small as a single silicalite nanoparticle thick line, that is approximately 500 nm. This approach has the ability of patterning very small features on silicon substrate, but the drawback is the long patterning time and lack of electron beam stability during long pattern formation process. Accordingly, it is almost impossible to form large patterns with electron beam lithography systems. Afterwards, to have full control on surfaces with differentiated areas on solid substrates, patterns of one type of zeolite crystals was formed on the monolayer of another type of zeolite layer with electron beam lithography for the first time. The same closed packed and highly oriented silicalite patterns were successfully formed on zeolite A monolayers and vice versa. Then photolithography technique was combined with direct attachment methodology to overcome the problem of the lack of total patterned area. With this technique, it was possible to pattern the whole silicon wafer in a couple of seconds, however the feature size of the zeolite patterns was limited with the infrastructures of the mask fabricated for photolithography studies. In this particular study, zeolite lines patterns with a minimum of 5 &micro / m thickness were prepared and the total patterned area was kept constant at 1 cm2. Similar to what was obtained by electron beam lithography study, zeolite A patterns were formed on silicalite monolayers with the minimum feature size of 5 &micro / m and vice versa. In the second part of the study, zeolite films were prepared on the transducers of conductometric biosensors using dip coating technique and named as Zeolite Coated Transducers (ZCT). Electrodes prepared using a mixture of zeolite and enzyme solution and then subjected to casting using glutaraldehyde were called Zeolite Membrane Transducers (ZMT). The operational and storage stabilities were determined to be in an acceptable range using ZCTs for conductometric urea biosensors. It was observed that using electrodes fabricated by the ZCT technique enhanced the biosensor signals up to two times and showed a rapid response after the addition of urea to the medium when it was compared with Standard Membrane Transducers (SMT). This enhancement can be explained by the lack of GA layer on top of the film, which acts as a diffusion barrier and inhibits the activity of the enzyme. On the second part of this conductometric biosensor study, effect of zeolite modification with methyl viologen (MV) and silver nanoparticles (Ag+ and Ag0), as well as the effect of changing Si/Al ratio was investigated with three different zeolite Beta particles which have Si/Al ratios of 40, 50, and 60. There were no significant effect of MV modification on ZMTs and there was no response observed with Ag+ and Ag0 modified zeolites. However, it was observed that conductometric responses increased with increasing Si/Al ratio for ZMTs. This behavior can be due to an increased hydrophobicity and/or the increasing acidic strength with the increasing Si/Al ratio within the zeolite crystals. Also ZCTs showed higher responses with respect to both SMTs and ZMTs. When compared with SMTs and ZMTs, ZCTs had higher reproducibility due to the controlled thickness of zeolite thin film by dip coating, and the controlled amount of enzyme adsorbed on this film. In the third part of the study, effect of zeolites on cell proliferation with MG63 osteoblast cells and NIH3T3 fibroblast cells were investigated. For that purpose, zeolite A, silicalite, and calcined forms of these zeolites were patterned with photolithography technique onto silicon wafers. Three different patterns prepared for this particular study, which has 0.125cm2, 0.08825cm2, and 0.04167cm2 zeolite patterned areas on 1 cm2 samples. In that way, not only the zeolite type and effect of calcination of zeolites, but also the effect of zeolite amount on MG63 osteoblast cells and NIH3T3 fibroblast cells were investigated. Silicalite coated samples were observed to have higher amount of cells than zeolite A coated samples after 24, 48, and 72 hours of incubation. This may be referred to the hydrophilic/hydrophobic properties, surface charge, and/or particle size of zeolites. Also it is observed that higher zeolite amount on samples resulted in an increase in the number of cells attached to the samples. There was also a significant increase in the number of cells upon using calcined silicalite samples. Accordingly, it can be hypothesized that zeolite pores result in an enhancement of protein adsorption and proliferation, even if this only occurs at the pore openings. On the other hand, there was no positive effect of calcining zeolite A. This result was expected since there is no structure directing agent used in synthesis procedure of zeolite A, which again supports the fact that pores might have some role in cell attachment.