CATHODICALLY INDUCED TIME-RESOLVED LANTHANIDE(III) ELECTROLUMINESCENCE AT STATIONARY ALUMINUM DISK ELECTRODES

A time-resolved electroluminometer, which utilizes electrogenerated luminescence (EL) from disposable oxide-covered aluminium electrodes, is described in detail. The cathodic polarization of this disc electrode in aqueous electrolytes induces a faint background EL with peak emission at 570 nm and with a lifetime of 6-mu-s, This cell can be utilized to excite dysprosium(III), samarium(III) and terbium(III) by electrochemical means to their lowest excited singlet states and, thus, to produce lanthanide(III)-specific emissions. From the lanthanide(III) EL systems tested so far, a cathodically induced EL of 2,6-bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol-chelated terbium(III) with a 2.1-ms lifetime is the longest lived and can be efficiently discriminated against the background EL on a time-resolved basis using instrumentally simple time-resolved detection; this time-resolved terbium(III) EL makes possible the determination of terbium(III) even below the picomole level in aqueous solutions.