I'm trying to decide which baseline (sigmoidal or linear) would fit better to calculate the melting enthalpy. What could be considerend as a "significant" shift in the baseline (before and after peak)?
In my experience, a linear baseline will give a good fit if you deal with a single melting peak in a solid to liquid transition. However if the transition is of the type solid+liquid to liquid you must perfom a deconvolution of the peaks corresponding to the liquid and solid phase.
The melting enthalpy is the total peak area. In my experience, both baseline interpolations lead to similar values of enthalpy (the difference is usually well below the uncertainty of a routine DSC measurement).
On the other hand, the peak integral curve (partial peak area vs. temperature dependence) is more sensitive to baseline type.
The sigmoidal baseline is usually employed for reaction heat determination where the reactant(s) and product(s) differ in their heat capacity (e.g., epoxy curing etc.).
Linear baselines are more suitable for first-order transitions (melting etc.) where the baseline shift before and after the peak is caused by a difference in the heat transfer.
Thank you alll!
Thanks to your recommendations I finally could choose the correct baseline for my samples. Sorry for the belated answer.
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