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Extraction liquid-liquide modulée électrochimiquement et microextraction en phase solide de composés pharmaceutiques sélectionnés

Abstract : Conventional sample preparation methods for the determination of polar compounds such as liquid-liquid extraction (LLE) and solid phase extraction (SPE) are generally not effective because of their multiple steps, low recovery and high consumption of organic solvents. Thus, this thesis deals with the development of new sample preparation methods, i.e, electrochemically modulated liquid-liquid extraction (EMLLE) and bar-micro solid phase extraction (bar-μ-SPE) to determine selected pharmaceutical compounds, i.e., metformin (MET), buformin (BUF), phenformin (PHEN), and propranolol (PROP) having varied lipophilicity in biological samples. In the EMLLE method, the aid of electric field was utilized to extract the pharmaceutical compounds across the interface between two immiscible electrolyte solutions (ITIES). ITIES formed when two bulk solvents aqueous phase (lithium chloride) and organic phase (I,2-dichloroethane), both containing electrolytes are brought into contact. Transfer potential for each analyte was analysed by voltammetry. The trend of transfer potential followed their lipophilicity; propranolol < phenformin < phenyl biguanide < metformin. Extraction of the analytes was performed by applying fixed potential to the biphasic system using potentiostat for 15 mins. The extraction performance was poor. Design of another ITIES cell and imposing interfacial potential by chemical polarization was done to enhance the extraction performance of this method. Thus, the EMLLE technique based on application of interfacial potential due to the presence of different concentrations of tetramethylammonium ion (TMA+) as common ion in each phase was studied. The optimum extraction conditions for this method are, [TMA+]o = 10 mM, [TMA+]w = 0.001 mM, Vorg = 2 mL, pHsample = 9, rotation speed = 900 rpm, extraction time = 600 s. The optimised parameters for back-extraction are: [TMA+]back = 50 mM, Vfinal = 0.1 mL, pHback = 2 . Nearly 100 % extraction of targeted analytes was achieved, and the enrichment factor obtained was up to ~ 60 for biguanide compounds. In the bar-μ -SPE method, adsorbent and a tiny metal rod was placed in a polypropylene membrane bag. Among the various adsorbents studied, graphene and zeolite showed some potential. Thus, extraction conditions were optimised for each adsorbent and adsorbent mixture. Despite the optimisations, the extraction was low (5.03-39.2 %). Nevertheless, enrichment factors of 1.49 -14.9 were obtained. Both proposed methods were applied to the determination of the analytes in urine. On the whole, the newly proposed methods are simple and markedly reduced consumption of organic solvents.
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Maizatul Najwa Jajuli. Extraction liquid-liquide modulée électrochimiquement et microextraction en phase solide de composés pharmaceutiques sélectionnés. Chimie. Université de Lorraine; Universiti Sains Malaysia (Malaisie), 2019. Français. ⟨NNT : 2019LORR0127⟩. ⟨tel-02479399⟩

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