Co-oxidation reaction of hydrogen peroxide with phenol, 4-aminoantipyrine catalysed by metal tetrasulfophthalocyanines (MPcTs) has been studied by UV-vis spectroscopy in the presence and absence of microheterogeneous media. The rate of antipyrilquinoneimine dye formation depends on the nature of metal ion, pH, and microheterogeneous medium. Hence, the activation of hydrogen peroxide is in the following order: MnPcTs > FePcTs > ZnPcTs > CuPcTs > NiPcTs. In basic pH, the rate of dye formation is greater than the acidic pH and maximum rate is observed at pH 9.0. The role of microheterogeneous medium on the activation of MPcTs complexes towards higher rate value is found to be increasing the stability of metaloxo cationic radical and free radical species of 4-aminoantipyrine and phenol in the following order: SDS > TX-100 > CTAB. The enzyme mimic models also quantitatively sense the H2O2 compositional variations. (c) 2005 Elsevier B.V. All rights reserved.