For an inert sample, the DSC signal is proportional to the specific heat capacity of the material as shown by equation (1) :
DSC Signal = (Heating Rate) x (Sample Mass) x (Specific Heat) (1)
However, due to instrument imperfections, the calculation of specific heat capacity using equation (1) is not very accurate. For better results, the sample and a specific heat standard (usually sapphire) are run under the same conditions and the specific heat of the sample is calculated relative to the standard using equation (2):
DSC Signal (sample) (Sample Mass) x (Specific Heat sample)
—————————- = —————————————————– (2)
DSC Signal (sapphire) (Sapphire Mass) x (Specific Heat sapphire)
The specific heat of the sapphire is known with high accuracy in a broad temperature range, so the only unknown in Equation (2) is the specific heat capacity of the sample, which can then be easily calculated as a function of temperature.
Baseline repeatability of the DSC instrument is critical for high-accuracy specific heat measurements, which makes a DSC-only instrument with a fixed sensor the best choice. The accuracy of the specific heat capacity measurements with a good DSC instrument operated by an experienced user can be expected in the order of +/- 3% as shown in the figure below.
