Flow-injection determination of trace amounts of dopamine by chemiluminescence detection

A flow-injection analysis (FIA) for the determination of dopamine has been developed. The method is based on the inhibition effect of dopamine on the iron(II)-induced chemiluminescence (CL) of 10,10′-dimethyl-9,9′-biacridinium dinitrate (lucigenin). The presence of a non-ionic surfactant, polyoxyethylene (23) lauryl ether (Brij 35), caused an increase in the inhibition effect. The present method allows the determination of dopamine over the range 1×10−8–2×10−7 mol dm−3. The relative standard deviation was 0.7% for eight determinations of 6×10−8 mol dm−3 dopamine. The detection limit (S/N=3) was 2×10−9 mol dm−3 with the sampling rate of 40 samples h−1. The effect of other catecholamines and compounds of similar structure on the lucigenin CL reaction was studied: quinone, hydroquinone, norepinephrine, pyrocatechol and l-dopa suppressed the CL intensity.