STUDIES ON THE STABILITY OF THIAMINE AND ITS MODIFIED COMPOUNDS : (VI) DETERMINATION OF O, S-BIS (ETHOXYCARBONYL) THIAMINE IN THE PRESENCE OF ASCORBIC ACID

Abstract

It was found that the percentage recovery of O, S-bis (ethoxycarbonyl) thiamine (DCET) was decreased by the presence of ascorbic acid (AsA) when DCET was determined by the thiochrome method after preliminary treatment with alkali. This alkali-method was also interfered by hydroquinone and other compounds susceptible to oxidation. An explanation is proposed for the interference by AsA that DCET is converted by the alkali-treatment into thiochrome reaction-positive compounds, which are successively oxidized to thiamine disulfide (TDS) by the presence of AsA. This was supported by the fact that TDS was detected in the reaction mixture when DCET was treated with alkali in the presence of AsA. DCET can be determined without any interference when cysteine is preliminarily added before the alkali treatment to the sample solution containing DCET and AsA. Other methods for the determination of DCET in the presence of AsA are discussed.