| Abstract
| - Thiamine is presently one of the most attractive substratesused for sensitive fluorometric measurements of peroxides. Thiochrome (TC), a highly fluorescent product, isformed in enzyme-mediated oxidations. It is assumed thatH2O2 is nearly quantitatively converted to TC. The reactioncannot differentiate H2O2 from many other peroxides suchas methylhydroperoxide (MHP); to perform differentialmeasurements, H2O2 can first be selectively destroyed bya suitable catalyst such as MnO2. In substituting Ag2Ofor MnO2 to accomplish the selective destruction of H2O2,we achieved the stated objective but were puzzled by a3-fold increase in the MHP response in the presence ofAg2O. It was soon discovered that traces of dissolved Ag+and Hg2+ can dramatically increase the yield of TC in thisreaction from either H2O2 or MHP; the normal yield infact is only 20%. We present here a reaction scheme andkinetic model that adequately describes this behavior andshould provide a path to substantially increase the sensitivity of this important assay method.
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