This file (https://www.tainstruments.com/wp-content/uploads/TGA-Presentation-New-Mexico-Event.pdf.pdf) which is not a video, explains the principles of TGA data analysis, in case you are using a TA Instruments equipment.
Normally, with the data you gathered from your analysis, there is a posibility of also obtaining the derivative curves. Normally the derivative of the mass loss against temperature looks like peaks, each one corresponding to the each mass loss of your sample. Being this the case, it might be better for your needs, instead of trying to draw the slope line for each decomposition zone on your sample, maybe graph the derivative values to see everything in the form of peaks. In the file, there are some examples, specially in the middle section of the file.
Thank you so much, Dr Agustin, for the pdf. Unfortunately, we don't have this equipment in our lab; the lab engineer conducts our tests in a research centre. i downloaded the TA universal equipment to try drawing the slope but the file extensions .txt and.csv are not readable by the software. i tried to find a specific file converter to get the original extension of the TA equipment but nothing was useful. I am looking to draw the slope, either manually or using OriginLab software.
If you have a DTG curve, you can fit two curves (with mass loss) together in the plot and then mark the beginning and ending points of each mass loss zone before drawing the slope line. If not, the interpretation depends on the curve's behavior. (more information, reply to me with your email)