As I know, the method to make the baseline in DSC or DTA is generally used with two types as, one is running without sample and alumina holder, the other is without sample.
And after running with sample, just substract the baseline from result of with sample.
In my case, even though heating rate and cooling rate is same in every condition, step size of rising and cooling temperature was different with running with or without sample and holder.
So, I could not substract the baseline from my data.
How can I do in this situation?
I am not sure I fully understand the question. Do you mean for example that during the baseline run 'x' data points per minute were recorded where as the sample data was recorded at a rate of 'y' data points per minute?
If so you may be be able to interpolate the data points and this may allow you to subtract one from the other. Depending on your analysis software you can choose how many points between temperature A and temperature B you want to export from a 'splined' DSC trace. If you make these the same I suspect you could subtract pretty easily in excel for example. The main issue you would face would be if you have to few data points per minute such that you miss an event.
Ideally you would rerun the DSC making sure the collection interval is the same. That might be easier (assuming you have a DSC readily available).
Yes, you are right. What I mean was substracting the 'y' data such as heat flow like that.
If there is no method to choose the temperature step range, how can I do?
Thanks.
Actually, I have tried to do with the software of DSC machine already.
But, there was something wrong. So, now I am looking for another method.
The quality of the baseline (better to say "empty pan line") method depends very much on the quality of the DSC: The baselines of several runs (with same parameters) must be one on top of the other always before you successful can subtract the baseline from the sample run. The method you use (i.e. the software of the DSC or any mathematical or other evaluation software) does not matter.
Good luck
The attached figure may help to understand how the baseline subtraction should be done (see my remark above). It is necessary to have a DSC with stable baseline (i. e. empty pan and empty DSC measurements).
Another remark: every calorimeter needs some time to come to stable conditions when you switch from isotherm to heating or cooling. This time is in the region from 20 seconds up to 2 minutes. The measurement within this apparatus specific time constant cannot be evaluated, as it yields arbitrarily values. If you heat with 20 K/min and the apparatus needs 2 minutes to steady state condition you may not evaluate the first 40 Degrees in your run. If the time constant is about 30 seconds you should neglect 10 Degrees after starting the measurement the measurement. As you can see it depends on the apparatus whether 20 K/min is a too large heating rate or not. Generally the resolution of the apparatus is the larger, the larger the heating rate is.
You may want to check also:
https://www.researchgate.net/post/In-DSC-is-it-necessary-to-perform-different-calibrations-for-the-case-when-the-crucible-has-a-lid-or-not
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