it depends on the level of asking

if your technique is in a good level for your experiment and the reviewers question just for another opportunity of working simply your answer will be “you don’t have the access for such a technique “

other wise you are no in a good position

It is better to submit the samples for TGA and BET. Otherwise, in lieu of the analyses you can do the followings:

- If the adsorption isotherm follows the Langmuir model, you can use the data for the surface area calculation.

- If not, use Methylene blue as an analyte and do the sorption experiment. The monolayer adsorption data can be used for the surface area calculation.

c.f.

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Instead of the TGA, depending on the reason for the question, if you have enough sample, put it in a muffle at e.g. 800 oC and measure the weight loss.

Even you can put tens of samples in the muffle set at different temperatures and measure the weight loss of each sample. Finally, plot the weight losses versus temperature.

Thank u sir for your suggestion

If the techniques are not accessible to you, then just put in the reply "We don't have access to the instrument''

thank u so much all respected scholars

Dear Syeda Sumra Naqvi, it depends on how many samples you have for such TGA and BET surface area measurements. If publication of the manuscript is not terribly urgent, I would ask colleagues of another university in your area who have these methods available. If they agree on a collaboration with you, you could send them a few representative samples and see if you get interesting results. Of course this will delay the publication considerably, but it would certainly improve the impact of the work.