In my opinion you should trust the results of the TPD more than elemental analysis

i'm not sure about my answer, however i would annoce it.

The temprature programmed desorption is a method used generally to desorbe somthing witch is already inside your porous structure of your activated carbone, if i'm right untill this point, here you can not get this information.

if you used it as TGA, you get the mass loss at given temperature for given molecule

I have not use it before, just trying to figure out how it works. (& your answer is here ; the working principale)

For the elematel analysis, try to repeat the experiment at least three times and take the mean value.

11% and 36 % a ratio of about 3. it's perhaps not the same oxygene that you would analyse it.

I have done my best. Good luck

Mohammed-El Amine Benchaabane Please, could you explain more your opinion specially about thermogravimetric analysis (TGA)?

In fact I did it for my carbon and the TGA curve presented a weight loss (~30 %) from room temperature until 900 °C.

if i'm right, your structure before calcination contain hydroxyl functions as other function.

since you activated it, you will systematiclly remove oxygen or organic function formed by oxygen atom.

My question for you, is you skeletal stucture contain oxygen also, if you said 'yes' then what you have lost in TGA at 900 °C is attributed to decomposition phenomenon (i don't know the thermal stability of your adsorbant, however 30% it's not decomposition). So i would go with this presumption that the TGA carried out is on the carbone before activation process evenhere i could say it's related to more than just Oxygen. to conclude, 30% and 36% seem to close for me than 11%.

I hope i didn't say somthing wrong.

and i guess you should use Tga coupled to FTIR if you have this technique