title: Exploiting thermodynamic data to optimize the enantioseparation of underivatized amino acids in ligand exchange capillary electrophoresis.
abstract: Stereoselective amino acid analysis has increasingly moved into the scope of interest of the scientific community. In this work, we report a study on the chiral separation of underivatized D,L-His by ligand exchange capillary electrophoresis (LECE), utilizing accurate ex ante calculations. This has been obtained by the addition to the background electrolytes (BGE) of NaClO(4) which renders the separations "all in solution processes", allowing to accurately calculate in advance the concentrations of the species present in solution and to optimize the system performances. To this aim, the formation of ternary complexes of Cu(2+) ion and L-lysine (L-Lys) or L-ornithine (L-Orn) with L- and D-histidine (His), and histamine (Hm) have been studied by potentiometry and calorimetry at 25 °C and with 0.1 mol dm(-3) (KNO(3)) in aqueous solution. The ternary species [Cu(L)(L-His)H](+) and [Cu(L)(D-His)H](+) (where L = L-Lys or L-Orn) show a slight but still detectable stereoselectivity, and the determination of ΔH° and ΔS° values allowed the understanding of the factors which determine this phenomenon. The stereoselectivity showed by the protonated ternary species has been exploited to chirally separate D,L-His in LECE, by using the binary complexes of copper(II) with L-Lys or L-Orn as background electrolytes added with the appropriate amounts of NaClO(4).
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Catania, Italy. acontino@unict.it
authors.forename: Annalinda
authors.initials: A
authors.lastname: Contino
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Maccarrone
authors.forename: Maurizio
authors.initials: M
authors.lastname: Remelli
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000596:Amino Acids