Silver-Induced Enhancement of Thiochrome-Based Peroxide Measurements

Jianzhong Li, Purnendu K. Dasgupta, Guigen Li, Shoji Motomizu

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Thiamine is presently one of the most attractive substrates used for sensitive fluorometric measurements of peroxides. Thiochrome (TC), a highly fluorescent product, is formed in enzyme-mediated oxidations. It is assumed that H2O2 is nearly quantitatively converted to TC. The reaction cannot differentiate H2O2 from many other peroxides such as methylhydroperoxide (MHP); to perform differential measurements, H2O2 can first be selectively destroyed by a suitable catalyst such as MnO2. In substituting Ag2O for MnO2 to accomplish the selective destruction of H 2O2, we achieved the stated objective but were puzzled by a 3-fold increase in the MHP response in the presence of Ag2O. It was soon discovered that traces of dissolved Ag+ and Hg2+ can dramatically increase the yield of TC in this reaction from either H 2O2 or MHP; the normal yield in fact is only 20%. We present here a reaction scheme and kinetic model that adequately describes this behavior and should provide a path to substantially increase the sensitivity of this important assay method.

Original languageEnglish
Pages (from-to)6753-6758
Number of pages6
JournalAnalytical Chemistry
Issue number23
StatePublished - Dec 1 2003


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