A rapid method for the analysis of N τ-methylhistidine in human urine

A novel, automated method is described for the determination of N τ -methylhistidine in human urine. The method uses a modification (H. Nakamura and J. J. Pisano (1976) Arch. Biochem. Biophys. 177, 334–335) of the reaction of fluorescamine with amines, which renders it specific for certain imidazoles. Interference due to histidine and histamine is selectively removed by prior reaction with aldehydes. The fluorescence yield for N τ -methylhistamine is 280, 440, 50, and 1.7, respectively. The concentrations of N τ -methylhistidine in human urine as determined by this technique correlate well ( r = 0.99) with those determined by ion-exchange chromatography. Furthermore, the technique is rapid (6–7 samples/h net throughout), is reproducible (coefficient of variation 1.8%), requires no prior treatment of the sample, and is implemented with widely available equipment.