Analytical Aspects of Energy-Deficient

A potential scan method has been developed for analytical studies of en-ergy-deficient electrogenerated chemiluminescence (ECL) in mixed systems. This method involves the use of an unsymmetrical ternating potential, one portion of which is held at a fixed negative potential, while the other is scanned over a l inearly increasing positive potential. This alternating po-tential program has been used to monitor the intensity of the ECL from 9,10-diphenylanthracene as a measure of the concentration of N,N,N',N'-tetra-methyl-p-phenylenediamine, N,N-dimethyl-p-phenylenediamine, and 10-methylphenothiazine solution. This ECL intensity was found to be l inear with concentration for these compounds for concentrations less than 0.1 raM. Because this method allows the recording of ECL intensity as a function of potential it represents the stationary electrode ECL equivalent of polarog-raphy. Electrogenerated aromatic radical cations and anions can undergo an electron-transfer r action in an aprotic solvent to produce electrogenerated chemilumines-cence (ECL). The radical cation and the radical anion can be formed from the same parent compound, as in the cases of 9,10-diphenylanthracene (DPA) or ru-brene, or from different parent compounds, as in the case of the mixed system of N,N,N ',N '- te t ramethy l-p-phenylenediamine (WBP) and DPA. The end result of the electron transfer, or any other subsequent reaction which ensues, is the production of first excited singlet-state molecules of one or both of the compounds. Be-cause ECL arises from first excited singlet-state emis-sion it is usually similar to the fluorescence of the parent compound. Two main pathways have been proposed for the pro-duction of excited singlet-state molecules of the com-pounds involved in the electron-transfer reaction. The first is an energy-sufficient pathway where the elec-tron-transfer reaction produces enough energy to di-rectly populate the first excited singlet stat