Determination of secondary amines as highly fluorescent formamidines by high-performance liquid chromatography

Aliphatic secondary amines were derivatized with the non-fluorescent reagent, 5-isothiocyanato-1,3-dioxo-2-p-tolyl-2,3-dihydro-1H-benz[de]isoquinoline in a simple and fast two step reaction via thioureas to highly fluorescent formamidines. Derivatives were separated by reversed phase liquid chromatography by using acetonitrile/phosphate buffer as the mobile phase. The limits of detection (S:N = 3) ranged from 200 to 300 fmol (20 μl injected). A method for the determination of dimethylamine, piperidine and diethanolamine in spiked acidic aqueous samples is given, after the decomposition of their N-nitroso derivatives.