Resolution of racemic glutamic acid mixtures

Optical isomers (enantiomers) are chiral molecules, which are commonly used in the drug and food industry. The major difference between the two D and L enantiomers is the spatial arrangement of atoms around a central carbon. During normal chemical synthesis a mixture of L and D enantiomers are formed in equally proportion (racemic mixture). Currently, the most common technique for resolution of a racemic mixture is chromatography using chiral specific columns. However, this method is limited in scale and is rather costly. This work studies the possibility for the resolution of racemic glutamic acid by crystallization. Since the solubility of the two enantiomers in water is the same, the separation is based only on the rate of crystallization by using appropriate seed crystals. Experiments are performed with a range of initial supersaturation ratios and seed concentrations. The results show that an appreciable resolution of racemic glutamic acid can be attained with the presence of L seeds in solution. At the highest seed concentration (10 g/L of L glutamic acid), the initial supersaturation of 3.60, 2.50 and 1.60 yields 24.0%, 42.1% and 55.5% pure L glutamic acid crystals, respectively. Therefore as the initial supersaturation is lowered the percent yield of pure L glutamic acid increases