Abstract : The separation of enantiomers is of a great interest in the pharmaceutical, chemical and food fields. Aptamers have been used by the Department of Molecular Pharmacochemistry (DPM) as new target-specific chiral selectors. These oligonucleotides, RNA or DNA, selected by SELEX (Systematic Evolution of Ligands by Exponential Enrichment), have the ability to bind their target molecules with an affinity equal (or superior) to that retrieved with the antibodies. The aim of this work is to study the enantioselective properties of RNA and DNA aptamers by micro-HPLC and CE. A chiral stationary phase L-RNA aptamer anti-D-histidine was designed using an immobilization strategy based on the biotin-streptavidin link. A novel covalent strategy for the immobilization of the aptamers was developed to enlarge the conditions of use and to improve the stability of these aptamers columns. The use of these new chiral selectors was then spread in an analysis by CE. The first study was accomplished using an L-RNA aptamer anti-D-arginine characterized by a very weak constant of dissociation (Kd = 330 nM) and a very high enantioselectivity (α = 12000). This study allowed to appreciate the special characteristics of this aptamer and to extend its use in an enantioselective competitive assay. An enantiomeric impurity as low as 0,01% was achieved. A similar assay, where a direct contact between the aptamer and its enantiomer target is favoured, allowed to increase the method sensitivity and could allow to reduce the detection limit thanks to the use of a fluorescence detection.