Antioxidants are widely used to protect organic materials from damages caused by autoxidation, an oxidation process that occurs under normal aerobic conditions. In this thesis, novel multifunctional organoselenium and organotellurium antioxidants were designed, synthesized, and evaluated in search for compounds with better radical-trapping capacity, regenerability, and hydroperoxide-decomposing ability. Selenium was incorporated into ebselenols and hydroxy-2,3-dihydrobenzo[b]selenophenes and tellurium into diaryl disulfides and aryltellurophenols. All newly developed antioxidants were evaluated in a chlorobenzene/water two-phase lipid peroxidation system containing suitable co-antioxidants in the aqueous phase. Ebselenol carrying a hydroxyl group (OH) ortho to selenium showed a two-fold longer inhibition time than the reference α-tocopherol in the presence of aqueous-phase ascorbic acid. 2,3-Dihydrobenzo[b]selenophenes carrying a 5- or 7-OH outperformed α-tocopherol both when it comes to radical-trapping capacity and regenerability. Alkyltellurothiophenols, in situ formed from their corresponding disulfides by tris(2-carboxyethyl)phosphine, were also efficient regenerable radical-trapping antioxidants. The consumption of N-acetylcysteine in the water phase was followed and found to be limiting for the duration of the inhibition. The hydroperoxide-decomposing ability of all organoselenium antioxidants was evaluated. Ebselenols were often better glutathione peroxidase mimics than the parent. In an effort to find out more about antioxidant mechanisms, aryltellurophenols carrying electron donating and electron withdrawing groups in the phenolic or aryltelluro parts were synthesized and OH bond dissociation enthalpies, BDEO-Hs, were calculated. Compounds carrying electron donating groups in the phenolic or aryltelluro part of the molecule showed the best radical-trapping capacity. Deuterium labelling experiments suggested that hydrogen atom transfer could be the rate-limiting step in the antioxidant mechanism.

Based on the linear relationship between concentration of H2O2 and the decrease of electrochemiluminescence (ECL) intensity in a Ru(bpy)32+/TPA system, procedures for the indirect determination of glucose with a flow injection analysis were developed. By passing solutions of glucose through a FIA system containing a glucose oxidase (GOx) immobilized sol-gel column and an ECL system of Ru(bpy)32+ and TPA, glucose can be determined optimally with a detection limit of 1.0 £gM in a linear dynamic range of 1.0 ¡V 200.0 £gM. A repetitive injection of glucose (100 £gM) and human serum solutions gave satisfactory reproducibility with relative standard deviations of 1.3 (N=31) and 3.9 % (N=42) respectively. Interference due to the presence of ascorbic acid, uric acid or other reducible agents in solution can be corrected by passing sample solutions through another sol-gel column that contained no GOx. From the agreement between the contents of glucose in human serum and soft drink analyzed by the developed method and those obtained by the spectroscopy method based glucose assay kit and satisfactory recovery of glucose from interferent containing solutions, the feasibility of the developed method for real sample analysis was confirmed. One of the major purposes of this study was to develop new immobilization approaches and flow cell designs for the fabrication of regenerable ECL-based sensors with improved sensitivity, convenience and long-term stability. Silica particulates were used as immobilization support in ECL sensors for TPA and NAD(P)H and in biosensors for glucose and glucose-6-phosphate¡]G6P¡^. The first ECL flow cell was fabricated from a glass tube, and a platinum wire was used as working electrode held at +1.3 V. The volume of the flow cell was about 50 £gL. An Ag/AgCl electrode and a piece of Pt wire were used as the reference and counter electrode respectively and placed downstream of the working electrode. Ru(bpy)32+ immobilized silica particulates with 1/3 silica sol content showed the best performance for TPA determination, and the sensitivity of TPA determination was dependent upon the amount of Ru(bpy)32+ immobilized in silica particulates. The lowest level of analyte detected for TPA was 0.02£gM, and linear range was from 0.02£gM to 5£gM. Up to a certain concentration level, it was found that Ru(bpy)32+ was tightly held in silica particulates and did not leach out into aqueous solutions, even with continuous flow for up to ten hours. Ru(bpy)32+ immobilized silica particulates were characterized of well activity and high stability; that stored at 0¢J exhibited its original activity for up to one year. The second ECL flow cell was fabricated from a piece of epoxy block supported Pt electrode (1 ¡Ñ 2 cm) as counter electrode, a piece glass window and a polyethylene spacer with 78 £gL cell volume, two 2.0-cm length of 0.6-mm diameter platinum wires were used as working electrodes held at +1.1 V, and an Ag/AgCl electrode as reference electrode. All three electrodes were incorporated within the main body of the cell. One of the biosensor design packed Ru(bpy)32+ incorporated silica particulates in the ECL flow cell, and a glucose dehydrogenase (GDH) immobilized silica sol-gel column is placed between the sample injection valve and the flow cell. The ECL response to samples containing glucose and cofactor (NADP) results from the Ru(bpy)33+ ECL reaction with NADPH produced by glucose dehydrogenase. This ECL biosensor was shown applicable for both NAD+- and NADP+- dependent enzymes, where NADH detection ranged from 0.50£gM ¡V 5.0 mM NADH and NADPH detection ranged from 1.0£gM - 3.0 mM NADPH. Glucose can be determined in a linear dynamic range of 5.0 - 500 £gM. Another biosensor design immobilized glucose-6-phosphate dehydrogenase¡]G6PDH¡^onto the Ru(bpy)32+ -doped silica particulates through silica chemistry and then packed these particulates into the ECL flow cell. By passing samples containing G6P and cofactor (NAD) through the ECL flow cell, G6P can be determined in a linear dynamic range of 10.0 £gM-1.0 mM. The regenerable ECL biosensor was characterized of good reproducibility and well stability for flow injection analysis. A repetitive injection of NADH (100 £gM) and G6P¡]500£gM¡^gave satisfactory reproducibility with relative standard deviations of 2.8 %¡]N=105¡^and 2.8 % (N=40) respectively.

Le réchauffement de la planète est une préoccupation mondiale à notre époque. Celui-ci peut s’expliquer en partie par les grandes émissions de CO2 dans l’atmosphère depuis le début de l’industrialisation. Parmi les plus grands émetteurs de CO2, il y a entre autres les véhicules motorisés, le chauffage au charbon et les raffineries de pétrole. Depuis quelques années, un processus commence à être utilisé pour réduire les émissions de CO2 atmosphérique. Ce processus est la capture du CO2 par des solvants aminés régénérables. Dans le cadre de ma recherche, des échantillons d’un solvant aminé qui ont subi un traitement de capture et de régénération du CO2 et qui ont passé différents temps dans ces processus ont été analysés pour déterminer les différents produits de dégradation de ce solvent. L’identification des produits de dégradation permet d’optimiser la méthode de capture du CO2 pour éviter leur production et donc garder son efficacité le plus longtemps possible. La chromatographie liquide couplée à la spectrométrie de masse (LC-MS) a été utilisée pour séparer et identifier les différents produits de dégradation. L’utilisation de la spectrométrie de masse à haute résolution (HRMS) a permis l’identification des formules chimiques les plus probables pour les produits de dégradation présents. L’ajout d’une cellule de collision à la HRMS a permis d’obtenir plus d’information par fragmentation sur les différents groupes fonctionnels et donc sur la structure des composés inconnus. Lorsque les structures possibles sont peu nombreuses pour une telle formule chimique, des étalons ont été utilisés pour comparer les spectres obtenus et confirmer les structures. Pour les composés ayant trop de possibilités de structures moléculaires, d’autres méthodes d’analyse ont été effectuées, telle la chromatographie gazeuse couplée à la spectrométrie de masse (GC-MS), la spectrométrie à mobilité ionique et la spectroscopie à résonnance magnétique nucléaire (NMR) suite à une collecte de fractions en chromatographie liquide. Au final, aucun nouveau produit de dégradation n’a pu être identifié avec une certitude de 100 %. Le niveau de confiance envers la structure proposée est par contre assez élevé pour certains d’entre eux, mais la difficulté d’obtention d’étalons rend l’identification assez exigeante. L’ensemble de ces travaux de mémoire a été réalisé dans le cadre d’un partenariat industriel. Une autre partie du projet était le développement d’une méthode pour détecter et quantifier deux N-nitrosamines à une concentration de 1 µg/L. La validation de la méthode pour la quantification des nitrosamines a également été effectuée. Les deux nitrosamines sont des résidus des processus de dégradation des amines du partenaire industriel et il est recommandé que leur concentration soit inférieure à 1 µg/L lors du rejet des eaux usées dans une étendue d’eau naturelle (US Environnemental Protection Agency). Il est donc important de les déterminer pour éviter de contaminer les cours d’eaux. La méthode développée utilise une extraction liquide sur support solide comme préparation d’échantillon ainsi qu’une méthode LC-MS pour la séparation et la quantification. La plus grande quantité retrouvée d’une des deux nitrosamines est de 7,30 µg/L, ce qui est légèrement au-dessus des recommandations. / Global warming is one of the most important concerns of this century. It can be associated in major part to CO2 emissions into the atmosphere since the beginning of industrialization. The major CO2 emitters are motorized vehicles, coal heating and oil refineries. Some years ago, a scrubbing process started being used to reduce atmospheric emissions of CO2 from coal burning plants. This process is known as CO2 capture by regenerable amine-based solvents. As part of this master’s research, samples from an amine-based solvent that was subjected to CO2 capture for different amounts of time during the capture regeneration process were analyzed to determine the various degradation products formed from the capture solvent. Identification of the degradation products and their kinetics of formation allow optimization of the CO2 capture method, ideally to avoid their formation and to maximize the efficiency of the capture process over a longer period of use. Liquid chromatography coupled to mass spectrometry (LC-MS) was used to initially select various degradation products present in reasonable abundance. The use of high resolution mass spectrometry (HRMS) allowed the identification of the most probable chemical formulas for the degradation products found in the capture solvent. Addition of a collision cell to HRMS provided more information on the different functional groups by MS fragmentation, and therefore more structural information on the unknown compounds. When there were a few possible structures for a single unknown compound, standards were used to compare the MS spectra obtained and confirm the structures. For the unknown compounds with too many plausible structures, additional analysis methods were used, like gas chromatography coupled to mass spectrometry (GC-MS), ionic mobility mass spectrometry and nuclear magnetic resonance (NMR) after fraction collection by preparative liquid chromatography. No degradation products were identified with 100 % certainty. The level of confidence towards proposed structures was quite high for some of the unknowns; however, the standards needed to confirm their identification were too costly to synthesize. This entire master’s project was carried out in collaboration with an industrial partner. A secondary part of this master’s project involved the development of a method to detect and quantify two N-nitrosamines at a concentration of 1 µg/L. Validation of the method for the quantification of the two N-nitrosamines was also carried out. The two analytes were residues of the degradation process of a different amine-based CO2 capture solvent where the recommended concentration of the residues should be under 1 µg/L when releasing the wastewater into environmental waters (US Environnemental Protection Agency). It is therefore important to determine these N-nitrosamines to avoid contamination of water bodies. The developed method used solid-supported liquid-liquid extraction (SLE) for sample preparation and LC-MS for separation and quantification. The highest amount of one of the two N-nitrosamines found in the samples supplied by the industrial partner was 7.30 µg/L, which was over the recommended level.