CALORIMETRIC STUDY OF THE DIPALMITOYLPHOSPHATIDYLCHOLINE/WATER PHASE DIAGRAM.

The dipalmitoylphosphatidylcholine (DPPC)/water-system was studied by did differential scanning calorimetry between 0. 1 and 17 weight percent of water and from 22 degree C to 142 degree C. Main emphasis was directed towards the exact determination of the water content. This was achieved by a moisture meter based on the Karl-Fischer method. The scanning curves exhibit up to 6 transition lines altogether. In order to study the variation of transition temperatures with the water concentration, heating and cooling curves of one sample were run repeatedly up to 57 times. A small leakage of the ds sample capsule allowed for a very small water loss at each scanning cycle leading to a continuous decrease in water content at each leakage of the sample capsule allowed for a very small water loss at each scanning cycle leading to a continuous decrease in water content at each scanning run. The water content was thus changed from 5. 5 to about 0. 5 weight percent. A phase diagram of the DPPC/water-system is scanning run. The water content was thus changed from 5. 5 to about 0. 5 weight percent. A phase diagram of the DPPC/water-system is established.