* * * INSIGHT * * *

Thermal Analysis - DSC or DTA

By

Thomas A. Jennings, Ph.D.

Although the field of lyophilization or freeze drying is not without its areas of controversy - which I happen to view as a healthy sign - nonetheless there appears to be at least one area of common agreement, i.e.,  the need to thermally characterize a substance so the freezing and primary drying processes can have a rational basis. In my opinion, such a thermal characterization is necessary prior to even opening the door of the dryer. Any attempt to try and lyophilize a product without any knowledge of the thermal characteristics forces one to use the good old “trial and error” method which has been considered in a previous INSIGHT ( Vol. 2 No. 8)

While there are certainly numerous thermal properties of the substance that one can determine [1],  I feel that one should know at least the very basic thermal properties which are in my opinion; (a), degree of supercooling,  (b), collapse temperature (sometime referred to as the glass transition temperature) or eutectic temperature ( should one even exist) and (c), the degree of crystallization. These thermal properties have already been described; however, for those not familiar with these terms it is suggested that you see [1] and  INSIGHTs (Vol. 1 No. 10, Vol. 2 No. 1, Vol. 5 no. 5). The need for the measurement of such thermal properties is beyond the scope of this INSIGHT. Instead, this INSIGHT will address the issue as to whether one should use either the DSC or DTA method to determine such properties. In preparing this INSIGHT, I have assumed that the reader is already well familiar with these two analytical techniques. If you are not familiar with such techniques, it is suggested that you review Chapter 6 of reference [1].

Vol. 5 No. 6                                                                                                       June 2002

4 Pages          1 References           0 Figures

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