The answer is the quantity of mass depend on you equipament. In general I run samples between 0,1 and 0,2 g to BET surface areas aroun 1000 m2/g. If you choose to run porosimetry simultaneously taking the time spent in the analysis is between 12 to 24 h takin P0 in each point, if your equipment is capable for is a good choice, because during 24 h the ambient pressure sometimes changes between 10 to 20 mmHg.

Thank you Joao G.R. Poco

Hi Prachi Awasthi

For the specific surface area determination, I have run the NOVA touch 4LX (F/W ver. 1.05, Serial#17018101901), Quanta chrome, USA by the N2 adsorption/desorption method at a liquid N2 temperature of 77.350 K. I have used a 0.1-0.18 g sample for the determination. I have performed the test for the powdered sample. Please have a look at the instructions for the machine that you are going to use. That will help you.

Regards

Dear Prachi,

For BET measurements amount of samples depend on equipament your are using as noted by Dr. Poco. However, in general less tha 0.5g sample is enough for almost all modern BET instrument. The key point is degas temp.

Hi Arnab Mukherjee , Santosh K. Tiwari ,

We have two Quantachrome® ASiQwin™ machine for BET measurement. The different machine operator uses my sample two times with the different amounts of samples. The first operator uses a 130 mg sample and gives the specific area around 450 m^2/g and the second operator uses a 30 mg sample and gives a specific area around 200m^2/g with the same degassing temperature. So, I want to actually know does the mass of the sample can differ such a large amount in specific area calculation?

what is mass of sample should be taken for good results in the specific area?

My sample is Boron nitride.

Thanks

Joao G.R. Poco Thank you Sir!

what are the key parameters which need to be focused on for specific area measurement when you want a high specific area?

Pretreatment temperature and vacum. We use (stopper cork) in all steps of mass quantification to avoid reexposure to umidity and cleaness.

Prachi Awasthi You should not see such huge difference between the same sample using different mass. Did I get it right that the samples were run on different instruments? Why not switch instruments and run both masses on both instrumnets? Up to me the difference is an instrumental problem.

Henrik Romar Yes sir! samples were run on different instruments.

Joao G.R. Poco and Sir, How to decide that pretreatment temperature for a particular material. My sample is Boron nitride nanosheets(BNNS).

First you have to decide what mas you have to use. What is the error of the balance? 1 mg; 0,1 mg? The cell is clean? How it is clean? Is it dry? Suposing you decide to use always 100 mg of a standard material. You should have some standard materials of different surface areas (primary or secondary) to evaluate the repetibility and reprodutibility of your equipment. You should build a "control graph" where you put your periodic standard measures. It is a good pratice to do not have doubts.

I suggest you try to increase temperature of pretreatment under vacum until the maximum vacum is attained. Do the BET measure for all temperature. Build a graphic and get your answer. Publish your finds.

Thanks, Joao G.R. Poco Sir