A new method of determining biacetyl in aqueous solutions by quenching its room temperature phosphorescence sensitized by α-bromonaphthalene in CTAB micelles is presented. CTAB micelles facilitate the triplet-triplet state energy transfer between α-bromonaphthalene and biacetyl is 1.76×10^9(mol.dm^-^3)^-^1s^-^1 and the quenched rate constant of biacetyl phosphorescence by CTAB is 7.82×10^7(mol.dm^-^3)^-^1s^-^1. The detection limit of biacetyl is 2.8×10^-^8mol.dm^-^3.

Key words: QUENCHING EFFECTS, SENSITIZATION, PHOSPHORESCENCE, NAPHTHALENE HALIDE, DIACETYL