In the first part of this thesis, strategies for avoiding systematic errors when quantifying the main components in mixtures of solvents has been developed (paper I). It is shown that variations in density caused by variations in sample composition and/or volume contraction need to be taken into account. In this way, quantification can be improved. The second part (paper II-V) describes a number of new methods for the analysis of organic trace components present in gaseous or aqueous samples, after an overview of the most commonly applied sample enrichment techniques has been given. For the enrichment of volatile trace compounds from gaseous samples, the concept of open tubular trapping has been further developed. A simplified procedure for preparing ultra-thick film, sorptive open tubular traps (OTTs) is described (paper III). The traps are coated with an irregular film of PDMS, and it is shown that the performance in terms of breakthrough volume is only marginally affected by the use of such traps. In paper IV, it is shown both experimentally and with a theoretical model that the enrichment capacity of OTTs can be significantly increased by increasing the inner diameter of the traps. A fully automated procedure for high-capacity sorption enrichment of trace organic analytes present in water is also reported (paper II). Time-based non-equilibrium extractions are feasible, enabling fast extractions that still allow sub-ppt limits of detection. The high flexibility of the automated system makes it possible to sample from process streams or off-line sources. Finally, the development of a new 2-dimensional precolumn-backflush method for the analysis of polar volatile trace analytes in water is described (paper V). This concept is based on the action of a hygroscopic salt which has a strong affinity for water, in a precolumn. Organic trace compounds, such as volatile alcohols or ketones show little retention on the precolumn and are eluted ahead of the bulk amount of the water onto a capillary column for subsequent high resolution separation. The residual water is removed from the system by backflushing the precolumn. The procedure allows the direct injection of aqueous sample volumes of at least 100 µl, and the pre-fractionation is accomplished within only a few minutes. Quantification limits for selected polar trace components were in the low ppb-region.

Ce travail porte sur la contribution à la modélisation thermodynamique d'un atelier de purification d'acide acrylique. Après l'identification des principaux produits intervenant dans l'étape de purification et la collecte de leurs propriétés thermodynamiques disponibles dans la littérature, nous avons effectué une série de mesures expérimentales pour un ensemble de mélanges contenant des acides carboxyliques (en particulier : diagrammes d'équilibres liquide-liquide et équilibres liquide-vapeur, enthalpies d'excès et volumes d'excès). L'ensemble des données (nos mesures et les valeurs de la littérature) a été exploité selon deux approches de modélisation des équilibres liquide-vapeur : une approche symétrique (φ-φ) appliquée aux équations d'état de Peng-Robinson (P-R) et de PC-SAFT et une approche dissymétrique (γ-φ) appliquée aux modèles de coefficients d'activité en phase liquide NRTL, UNIQUAC et Van Laar associés à diverses équations d'état en phase vapeur (gaz parfait, Viriel, Hayden et O'Connell et Nothnagel). Nous avons finalement retenu le modèle UNIQUAC associé à la corrélation de Hayden et O'Connell en phase vapeur. Des nouveaux paramètres d'interaction ont été déterminés et conduisent à des résultats homogènes et satisfaisants en comparaison avec nos mesures expérimentales et aux données de la littérature. Ils permettent également de décrire convenablement les diagrammes d'équilibres liquide-vapeur et les volatilités relatives des mélanges étudiés / This work focuses on the contribution in the thermodynamic modeling of an acrylic acid purification unit. After identifying the main products involved in the purification step and collecting their thermodynamic properties available in the literature, we conducted a series of experimental measurements for a range of mixtures containing carboxylic acids(mainly liquid-liquid equilibrium and vapor-liquid equilibrium diagrams, excess enthalpies and excess volumes).The data set-our measurements and literature values-was used according to two approaches for modeling vapor-liquid equilibrium: a symmetric approach(φ-φ) applied to the equations of state Peng-Robinson (P-R) and PC-SAFT and an asymmetrical approach (γ-φ) applied to the models of activity coefficients in the liquid phase NRTL, UNIQUAC and Van Laar associated with various equations of state in the vapor phase(ideal gas, Viriel, Hayden O'Connell and Nothnagel). We have finally chosen the UNIQUAC thermodynamic model associated with the correlation of Hayden O'Connell in vapor phase. New binary parameters were determined and led to consistent and satisfactory results in comparison with our experimental measurements and literature data. These parameters can also be used to adequately describe the diagrams of vapor-liquid equilibrium and the relative volatilities of the mixtures studied