Absolutely correct - this result is not logical. Most likely this is an experimental error. However there is a very slight chance that your ionic liquid reacts with the sample pan and forms a volatile compound, so you lose some of the weight of your sample pan in addition to your sample. If you tell the world what the ionic liquid and the pan material are we'll all be smarter.

There must be an instrumental error. You should Calibrate your instrument and repeat your TGA experiment.

Yes almost certainly an experimental error. However, I would bet on the weighing procedure as the more likely problem. Specifically, since most ionic liquids are hygroscopic, I suspect some weight - in the form of condensed water - was added accidentally after the sample was weighed.

dear Mr. Emanuel & miss. Chitra i make several explements but i get similar results (5-8)% more than 100% excess?? and the time interval between weighting & experiment starting only few mints(3-5) mints

and i make new calibration before 2months ago

Hi Mohammed Serhan Theiab

You need to figure out what the problem is. I would try the following, in whatever order you find convenient:

a) Load your sample pan as usual but keep it on the analytical balance for 10-15 minutes, with the door to the weighing chamber slightly open, and record the weight every minute. This will give you an idea of the significance (or lack thereof) of hygroscopicity of the sample.

b) Perform a run like the previous ones, but weigh your empty sample pan on the analytical balance before and after the run, to rule out loss of mass from the pan itself.

c) perform a recalibration, as suggested by Chitra Sulkan

As an aside: It's a strange "ionic liquid" you have that loses ~1/2 of its weight between 150 and 200C. Ionic compounds should be much less volatile.

If you are not getting accurate results, try to do your measurements from another instrument @Mohammed Serhan Theiab

One of the possible explanations is, besides instrumental/calibration error, that your IL, being quite hygroscopic, is absorbing water between you weighing it and transferring to your TGA. The TGA shows at least 5% loss below 100°C, suggesting a solvent and7or water.

Abour the problem of a negative percentage value found at a TGA plot, you may possibly find helpful to check my answer given to another question: https://www.researchgate.net/post/Can_TGA_show_negative_percentage_value