The effect of the copper(II) salt anion in the Chiral Ligand-Exchange Chromatography of amino acids.
Due to the strong involvement in numerous biochemical processes, the separation and resolution of amino acids is a continuously challenging task. Among the experimental parameters affecting the performances in a Chiral Ligand-Exchange Chromatography (CLEC) environment, the effect of the copper(II) salt counter-ion has received very limited attention. Aimed at evaluating the Cu(II) counter-ion effect upon the overall chromatographic performances when the S-trityl-(R)-cysteine is adopted as the chiral selector for the coated stationary phase, a number of both organic (acetate, formate, trifluoromethane-sulfonate) and inorganic (bromide, chloride, nitrate, perchlorate, sulfate) salts has been engaged for the enantiomer separation of a selected set of aliphatic (Allo-Ile, Ile, Leu, Nor-Leu, Nor-Val, Val) and aromatic (AIDA, ATIDA, His, Phe, Phg, Tyr) amino acids. By varying the physico-chemical nature of the Cu(II) anion, a pronounced impact upon the resolution factor (R(S)) has been observed. Even if to a lesser extent, the enantioseparation factor values (alpha) underwent variation, as well. A molecular modelling investigation has also been carried out as a rationalization attempt of the observed chromatographic outcomes.
Natalini
Benedetto
B
Dipartimento di Chimica e Tecnologia del Farmaco, Università di Perugia, Via del Liceo 1, 06123 Perugia, Italy. natalini@chimfarm.unipg.it
Sardella
Roccaldo
R
Carbone
Giovanni
G
Macchiarulo
Antonio
A
Pellicciari
Roberto
R