Separation and purification of optically active substancc by crystallization

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Experimental study of aqueous solution of DL-Mandelic acid was carried out to observe solubility data less than 30 percent of L-Mandelic acid against DL-acid by the cooling method under atmospheric pressure. And the solubility curve for the range was more than 30 percent of L-Mandelic acid also observed by high pressure crystallization. From this observed data, a new effective optical resolution process was proposed as a combination between evaporation and high pressure crystallization. And optical resolution of L-SCMC (S-Carboxymethyl-L-Cysteine) from DL-SCMC solution was studied at isoelectric point and supersaturated solution in which L-SCMC seed grew without nucleation of D-SCMC nuclei, was discussed. Crystal growth rate of a single crystal of L-SCMC was observed in aqueous solution of DL-SCMC with 5 and 10 wt% of NaCl for the range of supersaturation of 0.1-0.25 [g/100ml]. From these test's results, crystal growth rate of L-SCMC was affected by concentration D-SCMC "S_D" factor in the solution and disturb factor alpha which was defined by the ratio of supersaturation of L-SCMC to S_D, was proposed. On the other hand, concentration of only L-SCMC in the solution decreased by growth of L-SCMC seed which was added into supersaturated solution, for an initial period of operation just after L-SCMC seed was added, but when the operation continued for a long while, concentration of D-SCMC also started to decrease. This phenomenon was confirmed to come from nucleation of D-SCMC nuclei on the surface of L-SCMC aeed. Then, this nucleation was studied, and waiting time for two-dimensional nucleation of D-SCMC turned out to be affected by supersaturation of the solution and suspension density of crystal in the solution. Operational condition on which only L-SCMC crystal grows, was found out from this data. And crystal growth rate of L-SCMC seed was also observed by evaporatting crystallization and the data was compared with data obtained by cooling crystallization.