STUDIES ON THIAMINE PHOSPHATES : (IV) DIRECT CURRENT POLAROGRAPHIC STUDIES ON S-BENZOYLTHIAMINE O-MONOPHOSPHATE

Abstract

Polarographic behaviours of S-benzoylthiamine O-monophosphate (BTMP) were studied by direct current method and the following results were obtained. BTMP showed direct current polarographic waves in buffer solutions of pH 2-12. In the pH-range of about 4-7,two reduction waves were observed. The first wave was comparatively well-defined (E_<1/2>=-1.275 V us SCE at pH 7.0) and was more dependent on pH. The other was ill-defined and almost overlapped with the discharging current of the supporting electrolyte. It was found for the first wave to be irreversible (RT/αnF=68 mV) and controlled with diffusion process, by the various investigations on the nature of the wave in neutral buffer solutions. Fluorometry and crystallization of the reduction products and coulometry by a controlled potential electrolysis were carried out in order to define the electrode reaction of BTMP. It was indicated that the first wave was consisted of the reductional splitting of S-benzoyl radical of BTMP to give thiamine monophosphate (TMP) through an intermediate and the second showed the reduction of TMP to tetrahydrothiamine monophosphate. The direct current waves of BTMP were not considered to be suitable for analysis of the substance because of the inferior forms of them and of the unfavourable influences of other thiamine derivatives such as thiamine hydrochloride or dibenzoylthiamine.