Microfluidic platforms allow the implementation of classical analytical operations at a mere fraction of the time, cost and resources required conventionally while granting the potential for measurements to be taken directly in the field by untrained personnel. Centrifugal microfluidic (CM) platforms, a subset of microfluidic platforms, use centrifugal force to direct liquid flow and perform a variety of analytical operations.Although the use of centrifugal force grants CM platforms many advantages such as a high degree of parallelism, the potential for portability, and the capability to pump liquids irrespective of their physicochemical properties, it creates a design paradigm that requires all platform operations to occur while the platform is in motion. Stopping a CM platform may result in unintended capillary induced flow in channels that can disrupt the intended operation and even cause a loss of sample. In accordance with this paradigm, it is important to develop measurement techniques that can be utilized while CM platforms are in motion. One measurement of importance is the volume of liquid aliquots inside a CM platform. The capability to measure volume directly on CM platforms in motion could allow experiments to quantify liquid flow in real time and avoid the use of volume metering chambers, which occupy valuable platform space. In this thesis, a new technique based on image segmentation was created to perform volume measurements on CM platforms in motion. Evaluation platforms containing a black contrast layer were fabricated and injected with liquid aliquots. High-resolution images of the evaluation platforms in motion were obtained with a high speed camera synchronized to a strobe light and the images were processed digitally. Platform images were then converted to an intensity space before image segmentation was applied to trace the inner contour of each liquid aliquot. The contour of each measured aliquot was filled and an area was computed. This area was ratioed against that obtained for a calibration volume located on the same image to obtain the volume of the aliquot.The volume measurement technique was characterized through experiments designed to test its precision and accuracy over a range of volumes. The results were found to be 1 and 2% respectively. Further characterization of the technique revealed its flexibility in regards to optical magnification, chamber shape, size and aspect ratio and platform rotational frequency. An investigation into the effects of surface tension on the method precision was also conducted. The applicability of the technique to liquids of various colours was successfully demonstrated. The versatility of the method should allow it to be used for a variety of applications including real time metering of volumes in platforms, quantitative monitoring of a design's performance in real time and the elimination of metering chambers in designs. / Les systèmes microfluidiques permettent la miniaturisation de techniques classiques d'analyse chimique en n'utilisant qu'une fraction du temps et des ressources requises conventionnellement. Ces systèmes offrent la possibilité d'effectuer des mesures directement sur le terrain sans avoir recours à un personnel qualifié. Des systèmes microfluidiques ont été développés qui utilisent la force centrifuge pour diriger le débit de liquides injectés et accomplir une variété de processus analytiques. Bien que l'utilisation de la force centrifuge accorde à ces systèmes plusieurs avantages tels qu'un haut niveau de parallélisme, un potentiel de portabilité et la capacité de pomper des liquides indépendamment de leurs propriétés physicochimiques, elle crée aussi un modèle de conception qui requière l'accomplissement de toutes les opérations analytiques pendant que le système est en rotation.En accord avec ce modèle, il est important de développer des techniques de mesure qui peuvent être appliquées pendant qu'un système microfluidique centrifuge est en mouvement. Une mesure importante est celle du volume de liquides injectés dans un système microfluidique centrifuge. La capacité d'effectuer la mesure des volumes directement sur des systèmes microfluidiques en mouvement pourrait permettre la quantification du débit de liquide en temps réel et éliminer le besoin d'utiliser des chambres de comptage qui occupent un espace déjà restreint sur le système.Dans cette thèse, une technique basée sur la segmentation d'images a été développée pour mesurer le volume d'aliquotes de liquide dans des systèmes microfluidiques en rotation. Des systèmes d'évaluation contenant une couche de peinture contrastante ont été conçus, fabriqués et injectés avec des aliquotes de liquides. Des images de haute résolution de ces systèmes en mouvement ont été acquises avec une caméra numérique à haute vitesse synchronisée avec une lumière stroboscopique et traitées numériquement. Ces images ont été converties à un espace colorimétrique de niveau de gris et segmentées pour tracer un contour autour de chaque aliquote de liquide. Ces contours ont ensuite été utilisés pour calculer l'aire de chaque aliquote qui a ensuite été divisée par l'aire d'une aliquote de calibration située sur la même image pour obtenir le volume de chaque aliquote. La technique de mesure de volume a été caractérisée par des études conçus pour tester sa précision et son exactitude pour différents volumes. La précision et l'exactitude obtenues ont été de 1 et 2 % respectivement. Une caractérisation supplémentaire de la technique a révélé sa flexibilité quant au grandissement du système optique, la taille, la forme et le rapport hauteur/largeur des chambres du système et la fréquence de rotation du système. Une enquête sur les effets de la tension de surface du liquide mesuré sur la précision de la méthode a aussi été effectuée. L'applicabilité de la technique à des liquides de diverses couleurs a aussi été démontrée avec succès. La versatilité de cette méthode devrait permettre son utilisation dans une variété d'applications incluant la mesure de volumes en temps réel, le contrôle quantitatif de la performance de designs de systèmes microfluidiques centrifuges en temps réel et l'élimination de chambres de comptage dans leur conception.

A detailed, unified description of electrocatalytic mechanisms at organic conducting salt (OCS) electrodes, tetrathiafulvalene tetracyanoquinodimethane (TTFTCNQ) and hexamethylenetetratellurafulvalene tetracyanoquinodimethane (HMTTeFTCNQ), has been presented. A wide spectrum of behavior is observed depending on the electrochemical and kinetic characteristics of the analyte of interest, the nature of the OCS, and the applied potential. Both direct electron transfer and indirect (homogeneous and heterogeneous) mediation mechanisms are shown to arise, depending on the experimental conditions. / The redox chemistry of the coenzyme, pyrroloquinoline quinone (PQQ), has been investigated in detail as a function of metal complex formation and pH. The characterization of PQQ and its metal complexes provides insight into the redox chemistry of the 15-lipoxygenase active site. / A biosensor involving the coupling of a PQQ-enzyme, methanol dehydrogenase (EC 1.1.99.8.), to a TTFTCNQ electrode has been developed. Characterization of this enzyme membrane electrode shows that the substrate-reduced enzyme is rapidly turned over at the TTFTCNQ electrode whereas no turnover is evident at a conventional electrode. Enzyme properties (K$ sb{ rm me},$ stability, T$ sb{ rm sensitivity},$ pH dependence, substrate selectivity), when interfaced to the electrode, are reported.

Research on electrochemical detection methods for electroactive species in flowing streams is focussing on improving selectivity without compromising sensitivity or detection limits. With this in mind an effective electrode would be one that can examine electroactivity at many potentials in the shortest possible time frame. This work has investigated this possibility by using a single low temperature isotropic carbon working electrode with a choice of three scanning techniques. The most familiar one is cyclic voltammetry which is known to generate a wealth of qualitative information. The other modes are pulse and square-wave cyclic voltammetry. These modified versions of cyclic voltammetry offer advantages in two additional domains. Electroactivity may be studied in two time frames, increasing the diagnostic power, and quantitative determinations are possible. The enhancements and limitations of these scanning methods were investigated based on data obtained from a variety of electroactive model compounds. The survey was performed in quiet and flowing solutions using flow injection analysis for the latter.

The role of mobile phase modifiers in supercritical fluid chromatography (SFC) and their effect on the separation process were investigated. A study of the influence of temperature and density on chromatographic behaviour in supercritical carbon dioxide and four modified carbon dioxide mobile phases demonstrates the importance of both density and mobile phase composition in controlling retention characteristics. The information gained from these studies was used to develop methodology for the separation and detection of a series of phenothiazinone compounds and an assay for L-615,919, 4-chloro-3H-phenothiazin-3-one, in plasma. The development of an analytical method for the analysis of sorbitan trioleate in pharmaceutical formulations demonstrates a unique application of SFC with flame ionization detection (FID) that is not possible by other chromatographic techniques. / The feasibility of an electrochemical detection system for SFC has been demonstrated. The design and construction of an electrochemical detector with a platinum ultramicro working electrode and factors influencing its performance are described.

Formaldehyde is an important intermediate in the gas-phase methane oxidation chain and plays an important role in the chemistry of the troposphere by influencing the odd hydrogen budget (HOx = HO + HO2), and thus the Earth's oxidative capacity. The evaluation of the importance of formaldehyde in atmospheric cycles requires accurate and precise measurements of its concentration in the atmosphere. In this work, the concentration of formaldehyde in unpolluted outdoor air will be determined using an on fibre derivatization-solid phase micro-extraction (SPME). This method consists of derivatizing formaldehyde to its pentafluorobenzyl oxime using 1,2,3,4,5-pentafluorobenzylhydroxylamine (PFBHA), extracting using SPME and then analyzing with gas chromatography with flame ionization detector. We herein present an improved methodology for detection of formaldehyde in ambient air using SPME and GC-FID, which gives a detection limit of 100-300 pptv, for our rapid, portable and environmentally benign technique. The developed methodology was used to measure the formaldehyde mixing ratios in chemistry labs (9.28 ± 0.26, 12.36 ± 0.11 ppbv), library (11.75 ± 0.57 ppbv), and basement of a building (6.79 ± 0.010 ppbv) and in a campus terrain (7.17 ± 0.040 ppbv). We observed a diurnal variation in the mixing ratios of formaldehyde measured in the city of Montreal. The implications of our results will be herein discussed. / Le formaldéhyde joue un rôle important en tant qu'intermédiaire dans l'oxydation du méthane dans la phase gazeuse ainsi que dans les réactions chimiques de la troposphère en influençant le budget de radicaux hydroxyle et donc la capacité oxydative de l'atmosphère. Afin d'évaluer l'influence du formaldéhyde sur les cycles atmosphériques, la concentration atmosphérique exacte est requise et ce nécessite une méthodologie précise pour prendre des mesures. Dans ce travail la concentration du formaldéhyde dans l'atmosphère non polluée est mesurée à l'aide d'une fibre de micro extraction phase solide (SPME). Cette méthode consiste à dérivatiser le formaldéhyde en son oxime de pentafluorobenzyl avec du 1,2,3,4,5-pentafluorobenzylhydroxylamine (PFBHA), suivi par l'extraction et l'analyse par chromatographie phase gazeuse équipé d'un détecteur à ionisation de flamme (FID). Nous présentons une méthodologie améliorée pour détecter le formaldéhyde dans l'air ambiant à l'aide de la SPME et du GC-FID ; nous achevons une limite de détection de 100-300 pptv. La méthodologie a été utilisée pour déterminer les taux de formaldéhyde dans des laboratoires de chimie (9.28 ± 0.26, 12.36 ± 0.11 ppbv), dans une bibliothèque (11.75 ± 0.57 ppbv), dans le sous-sol d'un bâtiment (6.79 ± 0.010 ppbv), et sur un terrain au sein de l'université (7.17 ± 0.040 ppbv). Des mesures prises en 2009 au mois de juillet montrent que le taux atteint dans la journée et la soirée étaient de 8-12 ppbv et de 5-7 ppbv, respectivement; la méthodologie permet également de discerner les variations temporales.

Several approaches to sample preconcentration combined with sample introduction by Direct Sample Insertion (DSI) into the Inductively Coupled Plasma (ICP) for ultra trace elemental analysis have been developed. A microcolumn based flow injection (FI) manifold was used with ICP Mass Spectrometry (MS) but performance was adversely affected by high and variable blank levels. / Physical preconcentration by depositing the sample as an aerosol into an inductively heated graphite DSI probe yielded detection limit improvements of over two orders of magnitude for ICP Atomic Emission Spectrometry (AES). Instrumentation was developed to automate the aerosol deposition preconcentration process, and this apparatus was used in conjunction with ICP-MS. Several of the aerosol deposition, DSI, and ICP parameters that impact on the performance of the technique were studied. Detection limit improvements averaged two orders of magnitude, and analysis of a river water reference material for 10 elements gave good results even at the part per trillion (pg ml$ sp{-1}$) level. / Investigations into direct analysis of the analyte-laden chelating resin by DSI-ICP-AES were carried out. It was clearly demonstrated that the determination of volatile elements was adversely affected by the effect of the pyrolysis products of the resin on the plasma excitation conditions.

The initial and principal topic of this thesis was hazardous waste destruction by inductively coupled plasma (ICP) assisted post-combustion. As an aside, direct solid sample analysis (DSSA) on powdered sample was to be studied. To perform this double task, an "analytical chamber", described in chapter 2, was designed and made. The project was still at the preliminary studies stage on the usefulness of Swann bands as a probe for the presence of carbon to carbon bonds (Chapter 2), when the lack of funding forced a reorientation on the DSSA project as the main topic for the thesis. Since ICPs are known to be poor particle digesters, a suitable solid-gas reactor had to be found. From this study (Chapter 3), the cyclone reactor appeared to be the best-suited type of reactor for this task. Unfortunately, micro-engineering and gas flow rate constraints imposed by the ICP forced the abandonment of the concept for a simpler one. / In parallel with the quest for a suitable DSSA reactor, a new calibration method, the tandem calibration method (TCM) was developed. The objective of the TCM was to achieve calibration of any sample introduction system with the use of classical liquid standards. The study showed clearly that not only did the TCM not bias the results, but it also automatically corrected for physico-chemical matrix effects in a manner similar to standard additions. Despite the fact that results presented in Chapter 4 were obtained on liquid samples, the TCM is equally applicable to solid samples introduced into the plasma by other means. The TCM was used on an electrothermal vaporizer (ETV) (see Appendix 3). / The first DSSA system studied was modified direct sample insertion (MDSI). The MDSI used halogen-assisted sample vaporization and demonstrated that quantitative vaporization of solids could be achieved using the ICP as the thermal energy source (Chapter 5). The next step was to design a reactor along the same fines, but capable of operating under continuous sample feed from an appropriate powder feeder. This intraplasmic reactor, the pseudo fluidized-bed reactor (PFBR) did not perform as well as expected (Chapter 6). Still, it allowed the demonstration of the usefulness of a baffle placed in the path of the particles inside the reactor to achieve longer solid residence time. The results obtained on the PFBR indicated that although the general concept was good, the source of most problems came from inefficient energy transfer from the plasma to the reactor. This drawback was eliminated by replacing plasma heating with Ohmic (resistive) heating. Called the ohmically heated PFBR (OPFBR), this reactor imposed severe design constraints, principally in terms of electrode cooling and protection of the hot graphite reactor against attack from oxygen. The design required a series of modifications, described in Chapter 7, before reaching its final form (Chapter 8). Transport losses were a problem with the OPFBR. The introduction of a quenching gas through tangential holes in the upper body of the reactor faded to eliminate transport losses; however, these losses were sufficiently small and reproducible to allow quantitative analysis on real samples (SO-4 sod CRM and 1646 Estuarine sediment CRM) fed continuously into the reactor. These results fulfill the goal of this thesis, which was to develop a method for steady-state feed DSSA.

Two new techniques for the study of biological molecules using vibrational spectroscopy have been investigated, and are presented in this thesis in two parts. / In Part I, the application of centrifugal vacuum techniques for sample preparation in FT-IR spectroscopy is demonstrated. This technique is used in the development of an agglutination immunoassay for bovine serum albumin (BSA) using polystyrene latex particles as both a solid support and an IR label. The synthesis of new organometallic labels for use in LPIRIA has been undertaken and is described in detail. A competitive non-agglutination LPIRIA for BSA using anti-BSA covalently bound to carboxylate-modified latex (CML) particles has been developed. Protein-A, a universal antibody binder, covalently bound onto CML, is used in the development of a competitive non-agglutination LPIRIA for nortriptyline and for the titration of anti-theophylline by theophylline. / In Part II, the study of a variety of ($ eta sp{6}$-arene) chromium tricarbonyl complexes and cyclopentadienyl manganese tricarbonyl by FT-Raman spectroscopy is reported. The application of FT-Raman to the study of proteins, mycotoxins, latex particles, and selected drugs is also presented. (Abstract shortened by UMI).

Near-infrared optical spectroscopic measurement of samples is an important analytical tool for the determination of properties such as particle size, chromophore composition, and concentration. This information is invaluable for sample assessment in pharmaceutical, agricultural, and environmental areas. However, samples often exhibit significant light scattering, which complicates measurements. This thesis investigates chemometric approaches including power law and component analysis methods to extract useful sample information from data, while simplified instrumentation is developed to facilitate the acquisition of meaningful data. Photon time-of-flight (TOF) techniques allow sample optical properties to be estimated using temporally resolved measurements of short pulses of light. However, highly scattering samples, such as granular powders, are difficult to model. The shape of photon TOF profiles is largely influenced by the properties of these samples. A power law analysis technique was used to study TOF profiles, and a method was developed that could simultaneously determine analyte concentration and particle size. Compared to traditional steady-state measurements, a 3-fold improvement for absorption coefficient and up to a 5-fold improvement for particle size estimates was achieved. This analysis technique is applicable to a variety of areas including pharmaceutics, cosmetics, and chemical production. While methods exist for studying the optical properties of homogeneous optically scattering samples, those containing multiple layers present an interesting challenge for analysis. Spatially resolved measurements from layered samples contain information about the different layers present. However, complications arise when the layer to be probed is non-scattering. In a diffuse reflectance configuration, this type of layer does not provide information in the same way scattering layers do. An analysis technique was developed that allowed the separation of absorption and scattering components for such a layered sample. Accurate estimates of chromophore concentration were attained, even when an overlaying scattering layer had thicknesses that varied between 1 and 8 mm. This method has practical applications for medical, environmental, and industrial applications. A novel self-calibrating technique was developed for the estimation of absorbing species in a non-scattering layer embedded in a non-uniform scattering matrix. Spatially-resolved, steady-state, multispectral data were acquired from an optical head phantom with realistic topographical and optical properties. Experimental and mathematical techniques were developed that allowed accurate estimates of chromophore concentration. A limit of detection corresponding to 5 µL of blood in a volume of 150 ml of CSF was achieved. This system and technique can be useful for noninvasive medical measurements, especially cerebral bleed detection. The work presented in this thesis details key improvements for the spectroscopic analysis of homogenous and layered scattering samples. Each of these advancements represents a further development of our existing spectroscopic knowledge. Of particular interest within the medical community is the self-calibrating work, which can be used to developed noninvasive diagnostic techniques aimed at improving patient care. / La mesure par spectroscopie optique proche infrarouge est un outil d'analyse important pour déterminer les caractéristiques d'un milieu tel la dimension des particules, l'identification de chromophore, et leur concentration. Cette information est de valeur critique pour l'évaluation d'échantillons dans les domaines pharmaceutiques, d'agriculture et environnementaux. Certains échantillons, par contre, diffusent la lumière considérablement, compliquant la mesure. Cette thèse de doctorat examine des méthodes chimiométries comprenant les règles de puissance et les analyses de composante pour extraire de l'information utile d'échantillons à partir des données, alors que l'instrumentation simplifiée est développée pour faciliter l'acquisition des données signicatives. Les techniques utilisant le temps de vol (TDV) des photons permettent de jauger les propriétés visuelles d'échantillons en utilisant la mesure temporale résolue de courtes pulsations de lumière. Il est difficile, par contre, de trouver un modèle pour les milieux à haute diffusion telles les poudres granuleuses. La configuration du profile du TDV photonique est, en grande partie, influencé par les propriétés de l'échantillon. Une analyse des règles de puissance mathématiques fut utilisée afin d'étudier les profiles du TDV, et une méthode fut développée qui pouvait, simultanément, déterminer la concentration des substances sous analyse ainsi que la grandeur des particules. Comparé aux mesures uniformes de fonctionnement traditionnelles, les estimations du coefficient d'absorption futs amélioré par 3 fois et les estimations de grandeurs ont été améliorées par 5 fois. Cette technique d'analyse s'applique à des domaines variés telle la production de produits pharmaceutiques, cosmétiques et chimiques. Quoique des méthodes existent pour étudier les propriétés optiques de substances homogènes à caractères diffusants, les substances ayant de multiples couches présentent un défi d'analyse intéressant. Les mesures faites à des points variés sur l'échantillon à multiples couches donnent de l'information sur les différentes couches présentes. Par contre, la situation se complique lorsque la couche qui doit être sondée n'est pas diffusante. Une couche ayant un facteur de réflexion atténuée, ne révèle pas d'information de la même façon qu'une couche diffusante. Une technique d'analyse fut élaborée qui a permis la séparation des composants d'absorption et diffusants pour ce genre d'échantillon à couche multiple. Des estimations précises de la concentration chromophore ont été obtenues, même lorsque la couche supérieure avait une épaisseur qui variait de 1 à 8 mm. Cette méthode a une utilité pratique dans les domaines médicaux, environnementaux et industriels.Une technique à auto-calibration inusitée fut développée pour estimer les espèces absorbantes dans une couche non diffusante incorporée dans une matrice diffusante dissemblable. Des données multispectrales à point variées, et avec lumière continue ont été obtenues d'une tête optique fantôme ayant des propriétés topographiques et optiques réalistes. Des techniques expérimentales et mathématiques futs développées qui on permit des estimations précises de la concentration chromophore. Une limite de détection correspondant à 5 µL de sang dans un volume de 150 ml de liquide céphalorachidien fut atteinte. Ce système et cette technique peuvent être utiles pour les mesures médicales non invasives, plus précisément pour la détection de saignement cérébrale.Le travail présenté dans cette thèse de doctorat explique les améliorations saillantes pour l'analyse spectroscopique d'échantillons diffusants homogènes et à couches multiples. Chaque amélioration représente une augmentation de nos connaissances de la spectroscopie. La technique à auto-calibration est particulièrement intéressante pour la communauté médicale, car elle peut être utilisée pour développer des techniques non invasives pouvant améliorer le soin de patients.

This thesis explores four methods for improving quantitative diffuse reflectance spectroscopy in light scattering media. In the introduction theories of light propagation in scattering media, relevant instrumentation for measuring light scattering properties, spectral data processing methods, and spectroscopically active bioanalytes are outlined. Next, two novel instruments for practical scattering measurements, and two novel data processing techniques are presented. Finally, directions for future research into diffuse reflectance spectroscopy are suggested. A novel photon time-of-flight instrument is used to measure scattering coefficients in tandem with a portable diode spectrometer. Measured scattering coefficients are used to correct co-measured near infrared spectra for scattering and for improving quantification. Reduced scattering coefficients were measured with coefficients of variation of 11.6% at 850 nm and 14.1% at 905 nm. This allows practical correction of light scattering in point-spectra. Using scattering-correction, estimates of dye concentration were improved by 35%. A novel device imaging annular patterns is presented. This imaging instrument is used to measure reduced scattering coefficients and absorption coefficients. Reduced scattering coefficients were measured with a coefficient of variation of 12.6%, and absorption coefficients were measured with a coefficient of variation 50% lower than using traditional imaging methods. A novel method for using parsimony in the development of data processing methods using genetic algorithms is presented. Genetic algorithms have been used to identify spectroscopic data processing methods for complex samples. A / Cette thèse explore quatre méthodes pour l'amélioration de la spectroscopie de réflectance diffuse quantitative dans des milieux qui diffusent la lumière. En introduction, une description des théories de la propagation de la lumière dans des médias qui diffusent celle-ci, des instruments pour mesurer les propriétés de diffusion, des méthodes de traitement des données spectrales, et des bioanalytes avec activité optique est donné. Un nouvel appareil à «temps de vol de photon» est présenté. Cet instrument portatif est utilisé pour mesurer le coefficient de dispersion en tandem avec un spectromètre à diode portable. Les coefficients de diffusion mesurés sont ensuite utilisés pour corriger la dispersion dans les spectres infrarouges co-mesurée, ainsi que l'amélioration de la quantification. Les coefficients de dispersion ont été mesurés avec une variation de 11,6% à 850 nm et 14,1% à 905 nm. En prenant en compte la dispersion, les estimations de la concentration de teinture ont été améliorées de 35%. Un nouvel appareil utilisant les modes d'imagerie annulaire pour mesurer les coefficients de dispersion et d'absorption est présenté. Les coefficients de dispersion ont été mesurés avec un coefficient de variation de 12,6%, et les coefficients d'absorption ont été mesurés avec un coefficient de variation amélioré de 50% par rapport aux méthodes d'imagerie traditionnelle. Une nouvelle méthode pour améliorer l'utilisation des mesures de simplicité dans le développement de méthodes de traitement des données via des algorithmes génétiques est présentée. Les algorithmes génétiques ont été utilisés pour identifier les mét