Continuous-flow discrimination of L- and D-histidine Original Research Article

A continuous turbidimetric method for the sequential determination of L- and D-histidine is reported. The method is based on the decrease in the rate of crystal growth of L- and D-glutamic acid caused by the adsorption of foreign species (L- or D-histidine, respectively) at specific point of the crystal surface. The method provides a limit of detection of 3 and 5 mg/l for L- and D-histidine, and a relative standard deviation of 3%. The high selectivity and sensitivity of crystal growth inhibitory processes make them potentially useful for the enantiomeric resolution of inhibitory substances (e.g. L- and D-histidine). The proposed method was applied to the determination of L- and D-histidine in synthetic samples, containing both enantiomers in variable concentration ratios (from 1:1 to 1:30) with relative errors less than 3%.