Calibration of the Total and Reversing Signals

Sometimes the empty-pan baseline correction for heat capacity is omitted for the reversing signal because, when closely matched sample and reference pans are used, it is usually small. Whether this is adequate depends on the type of information being sought. For example, if all that is required is the glass transition temperature, then a full heat capacity calibration may be excessive. However, as an absolute minimum, a calibration must be performed to obtain a correction factor for the cyclic heat capacity at one temperature in the range of interest. 

It has become common practice to present MTDSC results both as heat flow and heat capacity within the same data set. Tjqjically, the greatest source of error is that from the empty-pan baseline for the average signal. Many workers, in order to save time, choose not to make this correction and then, almost by default, the total signal is presented as heat flow rather than heat capacity, because this correction has not been made. This is not necessarily bad practice. The experimenters may well be able to obtain the information they require without this additional calibration step. Consequently, one must take care when reading the literature to ascertain what types of data reduction and calibration have been carried out. The questions that must be asked are as follows. 

If some, or all, of the answers to the above questions are absent, this implies that a less than optimal procedure has been adopted One must form one s own judgement as to whether this lack undermines the conclusions that are drawn for a particular case. 

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