I am reviewing some TGA analysis papers in which a sample is decomposing. The values for the DTG curve appear positive, although from the TGA curve a weight loss is evident. Is it possible that the software is reflecting the sign so the graph is more readable?
Thanks
@ Faisal Mohammed
May be true and the reason may be due to oxidation effects or calibration problems. Make sure whether the atmosphere is inert and pure.
Usual result of TGA experiment is loss of sample weight due to drying, removal of volatiles, decomposition accompanied with formation and removal of volatile or gaseous components etc. TGA curves, showing weight of the sample as a function of temperature, in these cases present weight reduction. DTG curves (first derivative of the weight over the temperature) show rate of the weight losses as a function of temperature. That is, if no weight loss takes place - DTG is close to zero; if TGA detects weight losses - DTG starts deviate from zero in positive direction indicating non-zero rate of the weight loss. If during the test TGA curve detects weight gains (due to oxidation, for example), DTG curve will deviate from zero in negative direction, indicating “negative” rate of weight losses - weight gain.
I agree with Michael. I have seen substances gain weight due to oxidation, even though the instrument is set to desiccate the sample.
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