Turbidimetric flow method for the enantiomeric discrimination of L- and D-aspartic acid

Abstract

The proposed enantiomeric resolution of aspartic acid is based on the inhibition of the crystallization of L- and D-histidine. A flow-through system permits the turbidimetric multi-detection of the signal produced in the crystallization of histidine from a supersaturated solution. The presence of L-or D-aspartic acid delays the growth of L-or D-histidine crystals, respectively, the delay being proportional to the concentration of aspartic acid. Calibration graphs are linear down to 40 mg l^–1 of L-and D-aspartic acid, with a precision (repeatability, as RSD, n= 11) of 2.5%. The method was applied to the determination of L-aspartic acid in pharmaceutical preparations (spiked with D-aspartic acid) and the resolution of a racemic sample of D,L-aspartic acid. The results obtained were consistent with the nominal contents.