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Abstract:
According to the fact that the need of pure enantiomers in pharmaceutical industry, food industry, cosmetics and agrochemical industry is in tremendous increase, different separation techniques have been under investigation for production of pure enantiomers on a commercial scale.
In the last years attention is focused on the development of new highly selective chiral stationary phases (CSP's) used as packing material in chromatographic columns.
This work, which deals with the separation of racemic mixtures of amino acids using High Performance Liquid Chromatography (HPLC), can be divided in two parts.
The separation of the following α-amino acids: DL-Methionine, DL-Asparagine, DL-Leucine, DL-Serine, DL-Glutamine and DL-Valine was investigated experimentally. Three chiral CSP's were applied: Chirobiotic T (macrocyclic antibiotic-Teicoplanin CSP, Astec, USA) Diaspher- Chirasel-E (macrocyclic antibiotic-scientific sorbent Eremomycin CSP, BioChemMack S&T, Russia) and Chirex (ligand exchange-Cu CSP, Phenomenex, USA). Temperature and flow rate were kept constant, only the composition of the mobile phase was changed.
By taking into consideration the solubility of the amino acids, the cost of the solvent and the time needed for the separation the following systems were chosen for further work:
Chirobiotic T column (DL-Methionine, mobile phase: EtOH:H2O=40:60v/v and DL-Asparagine, mobile phase: EtOH:H2O=60:40v/v); Diaspher-Chirasel-E column (DL-Methionine, mobile phase: MeOH:H2O (0,1M NaH2PO4)=20:80v/v).
To estimate adsorption equilibria, the ECP method [1] was applied for determination of the singleenantiomer adsorption isotherms. Langmuir and bi-Langmuir isotherm model parameters were estimated. With the determined isotherms, simulation of the elution profiles was performed using the equilibrium-dispersive model[1].
The last goal of this work was the estimation of the production of D and L Methionine enantiomers (purity of 99%) and comparison between Chirobiotic T and Diaspher-Chirasel-E. Results obtained by this work form a good base for further intentions, like the application of these columns in a Simulated Moving Bed [1] plant.
References:
[1[ G. Guiochon, S.G. Shirazi, A.M. Katti, Fundamentals of Preparative and Nonlinear Chromatography, Academic Press, New York, 1994
