Purity and Recrystallization, Cholesterol

Sample

Cholesterol, various degrees of purity > 99% und > 95%

Application

Flavoring agent

Conditions

Measuring cell: DSC820

Pan: Aluminum 40 µl, hermetically sealed

Sample preparation: The sample was pressed down in the pan with a PTFE rod. The sample with the stated purity of >95% was purified by recrystallizing 3 times from methanol.

DSC measurement: Heating from 120 °C to 170 °C at 2 K/min

TGA measurement: Heating from 30 °C to 250 °C at 10 K/min, blank curve corrected

Atmosphere: Air, stationary environment, no flow

Interpretation

The diagram shows the melting curves of the three samples. The purities are evaluated using the purity determination according to van't Hoff. As an example, the detailed evaluation is described for one of the samples.

The purities determined are almost identical and are (also for the sample >95%) better than the manufacturer's specification. In this connection, it should be noted that DSC can only measure eutectic impurities, so that other impurities remain undetected.

Evaluation

Evaluation of the purity between 10% and 50 % of the peak height with baseline type ‘line’.

Conclusion

Products can be purified by recrystallization. The degree of purification can be quantified with a DSC purity determination, provided that we are dealing with a eutectic impurity.

_{Purity and Recrystallization, Cholesterol | Thermal Analysis Application No. HB835 | Application published in METTLER TOLEDO TA Application Handbook Pharmaceuticals}