[Study on the interaction between water-soluble vitamins by the "three-point-test" of differential scanning...

The physico-chemical compatibility of solid-state pharmaceuticals is mainly determined by their interaction. The "Three-point-test" of differential scanning calorimetry in which three samples of different ratios are determined is proposed to study this interaction, and the simplified judging rules are as follows: If there are two or less than two endotherm peaks in DSC thermogram for all 3 ratio samples, we may mainly consider the peaks at lower temperature. If these temperatures are the same, which would be monotectic system or simple eutectic mixture, there will be very weak interaction in their solid state, and these could be compatible. If the temperatures are different, which would be solid solution system or solid complex system, there would be interaction in their solid state. If there is no endotherm peak, or there are exotherm peaks or there are more than two endotherm peaks, they all indicate that there is a stronger interaction in their solid state and they are incompatible. As an example, the interaction between water-soluble vitamins--Vit B1, Vit B2, Vit C and nicotinamide was determined. The results indicated that only Vit C is incompatible with nicotinamide, as there is a stronger interaction, and with Vit B1, there is a weak interaction.