Sequential determination of D- and L-glutamic acid by continuous fractional crystallization

A method involving turbidimetric multidetection of the signal produced in the continuous crystallization of D- and L-histidine in the presence of an organic solvent is proposed, It uses the inhibitory effect of D- and L-glutamic acid on the crystallization of D- and L-histidine, respectively. Calibration graphs are linear down to 40 mg/L D- and L-glutamic acid, with relative standard deviations between 2.6 and 2.9%. The proposed method was used for the determination of L-glutamic acid in pharmaceutical preparations and the determination of D- and L-glutamic acid in a racemate of DL-glutamic acid.