Greetings! We use thermogravimetric analyzer TGA/DSC 3+ (Mettler Toledo) to study clay minerals, soils and other objects. Every single DSC curve we get (including empty alumina crucible, alumina samples) has a S-like baseline instead of classic straight DTA baseline (as you can see in the pictures attached to this text). We suppose it is so because our analyzer equipped with SDTA sensor which does not allow us to use a reference simultaneously with sample. Is this assumption correct and are there any ways to «straighten» DSC baseline in this case? We use subtracting of the DSC curve of the same sample heated to 1000°C, but its provided result is not ideal.
I'm sorry, I don't not have an answer. But I do some DSC and am wondering the same question! (I have a perkin elmer DSC7, and don't use a nitrogen purge)
I have no experience with MT DSC but you may check if the furnace is clean. You may clean it according to the protocol given. Else, the software should allow you to manipulate the data by straightening the line (but unsure if MT software has it).
You may want to check:
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
Hello, I agree with Choon Fu Goh , try to check if the furnace is clean. Also, check the sensor if it is clean and not damaged. And you can also try to use a new crucible.
There are 3 types of heat exchange between sample, reference and furnace: convection, conduction and radiation heat exchange. Consequently the gas flow, the thermal contact between pans and support and the surface of the pan (lid or no lid, identical pans) must be identical for sample and empty pan run to give reliable results. It is quit normal that every DSC has a different empty calorimeter baseline which often is not a straight line (because of unavoidable differences between the sample and reference sensors and their surroundings.
To get good results, the conditions of the sample- and the empty-pan-run should be as identical as possible (closed pans with lid of same type for both runs, etc).
For details see our book "Differential scanning calorimetry" from Springer-Publisher
i Have used DSCs that allowed for baseline flattening as part of the calibration routine. The full range of temperatures were used with an empty pan followed by saving the thermogram as the BASELINE file name in a certain folder. This run must also match the heat rate of the samples planned. Without a reference pan, this may be something you continue to battle if you use variable heating rates. The strangest baselines seemed to always point back to purge gas issues though. Once, a tiny leak gave all tests an exo peak just before melt that did not show on other instruments. No idea how, but re-securing the N2 line to a port in the unit fixed it.
Thank you all for your answers! Furnance contamination, gas quality and damaged sensor can be the reasons of our problem indeed, but apparently not in this case. Other specialists told me that such baseline curve's shape indeed cannot be straightened because of our SDTA sensor. If you want to get a straight baseline curve you need to purchase DSC sensor with six thermocouples instead of one without reference. Christopher Eugene Smith maybe the explanation I've been provided can be useful for you too
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