Stability of the o-phthalaldehyde-histamine complex

Abstract Three methods of derivatization of histamine with o -phthalaldehyde (OPT) reagent were compared in order to confirm the stability of the fluorescent product. A reversed-phase high-performance liquid chromatographic system with a fluorescence detector was used. Immediately after derivatization, samples were injected at intervals of 10 min for a total of 60 min. The stability of the fluorescent complex varied according to the method of derivatization. For method 1 (histamine-OPT reaction at ambient temperature) the peak area after 10 min was only half that of its original value. For method 3 (acidification with hydrochloric acid of the end-product of derivatization) only a slight decrease occurred over the 60-min period; method 2 (extraction of the OPT complex with ethyl acetate) was the most stable.