Tangential area-proportional baseline interpolation for complex-process DSC data - Yes or no?

Theoretical simulations were used to evaluate distortions arising from the usage of tangential area-proportional interpolation in certain situations corresponding the specific thermokinetic background courses. In particular, the effects of different types of complex kinetic peaks (consisting of overlapping sub-processes) and different heat capacity changes associated with the given sub-processes were investigated. Performance of the tangential area-proportional baseline was evaluated in terms of the magnitude of errors arising from the consequent kinetic analysis done on the basis of isoconversional methods and multivariate kinetic analysis. Apparent activation energy and pre-exponential factor were found to be only very weakly influenced by usage of tangential area-proportional interpolation in most of the commonly encountered inappropriate situations. On the other hand, the model-based parameters (kinetic model exponents or even preference of certain model) can be significantly affected by usage of tangential area-proportional interpolation without the exact knowledge of the true course of thermokinetic background. These errors increase with decreasing relative magnitude of the given sub-peak. Largest errors (up to 20%) were then associated with determination of the integral area of the kinetic peak (quantity related to the specific enthalpy of the process).