The effect of 36 phenols and anilines on typical luminol electrochemiluminescence (ECL) was systematically investigated under different pH in NaHCO₃-Na₂CO₃ and NaOH media. It was found that the enhancement and inhibition by phenols and anilines on the luminol ECL were related to the half-peak potential, the structures of the compounds and the pH of the medium. The compounds with higher half-peak potential did not influence the ECL. The compounds with lower half-peak potential and with —OH, —NH₂ on the para-position of the benzene ring, or with three adjacent —OH on the benzene ring showed enhancing effect at lower pH and inhibiting effect at higher pH. The other compounds showed inhibiting effect and the magnitude was related to the structure of the compounds. The half-peak potential of the tested compounds, the fluorescence and the ECL spectra of the system were studied. The mechanism for ECL inhibition and enhancement has been proposed. It is likely that energy transferring from the excited state 3-aminophthalate to the quinone or ketone or their polymer formed by electro-oxidation of phenols and anilines led to the inhibiting effect and the benzosemiquinone radical and produced during the reactions were responsible for the ECL enhancement.

Key words: luminol, electrochemiluminescence, enhancement, inhibition, phenol, aniline