Abstract
The quantitative determination of dihydrothiamine (DHB_1) using ferric chloride as its oxidant to thiamine is presented : 2 ml of the sample solution containing 1〜10μg of DHB_1 is kept for 30 min. at 40℃ after the addition of 1 ml of dilute H_2SO_4 and 0.2 ml of 20% FeCl_3 solution and then the solution is neutralized by NaOH. Thus formed thiamine is estimated by the usual cyanogen bromide method and the blank thiamine value of the sample by cyanogen bromide method is reduced from the former value. The transformation of DHB_1 into thiamine is about 65〜69% of the theoretical yield, although FeCl_3 gives the highest and most satisfactory result compared to such other oxidant as ferricyanide, ferric sulfate or nitroferricyanide. There exist two other isomers ; pseudo- and iso-DHB_1,beside the normal one. The higher yields of thiamine from pseudo-DHB_1 by this reaction is observed, while the same or a little higher yield from iso-DHB_1. Furthermore DHB_1 is unstable in the dilute acidic solution ; especially the pseudo-isomer is most unstable and the iso-isomer is more stable than the normal one.
