Simultaneous determination of histidine and histamine by second-derivative synchronous fluorescence spectrometry

Simultaneous direct determination of histidine and histamine in mixtures is described. The method is based on the formation of fluorescent condensation products with o-phthaldialdehyde in a basic medium in the presence of 2-mercaptoethanol. Both the conventional and synchronous fluorescence spectra of these condensation products completely overlap, making determination by either of these techniques impossible. However, the determination can be performed by second-derivative synchronous fluorescence spectrometry. The method is simple, rapid and inexpensive and the measurements are performed in a single scan. Calibration graphs are linear in the range 0.1-4.0 mug/ml for histidine and 0.06-5.0 mug/ml for histamine. Mixtures of histidine and histamine in ratios between 12:1 and 1:8 have been satisfactorily resolved.