Continuous kinetic method for the quantitative resolution of structural isomers of arginine and ornithine

A flow injection method for the determination of l-arginine and l-ornithine based on the inhibition of l-histidine crystallization was developed. The open-closed system used permits turbidimetric multidetection of the signal in the crystallization of l-histidine in the presence of an organic solvent (2-propanol). The proposed method permits the selective determination of l-arginine (0.3–12 mg 1−1) and l-ornithine (0,5–20 mg 1−1) in the presence of their d-enantiomers and other l-amino acids without the need for a prior separation. The relative standard deviation was ca. 2.3% (n = 11). Both amino acids were determined satisfactorily in pharmaceutical preparations, and their recovery after addition to samples was 100 ± 3%. The sampling frequency was 7 ± 1 h−1.