UV-visible spectroscopy studies of heteropolyacid (HPA) catalysts in solid were carried out with an aim of utilizing absorption edge energies as a probe of catalytic oxidation performance of the HPA catalysts. The absorption edge energies were correlated with the catalytic performance of HPA catalysts in the oxidative dehydrogenation of isobutyric acid. The correlation between catalytic oxidation performance and absorption edge energies of HPA catalysts demonstrated that the absorption edge energies could be utilized as a correlation parameter for the reduction potentials (oxidizing powers) of the HPA catalysts, and furthermore, as a probe of catalytic oxidation performance of the HPA catalysts. (c) 2006 Elsevier B.V. All rights reserved.