How to measure the small specific surface area <1m2/g?

Usually, there is a certain dead space in the instruments and devices used to measure specific surface area by adsorption method, and the size of the dead space determines the absolute error of the specific surface area measurement to a large extent. Therefore, the error in measuring small specific areas <1m2/g is relatively large. There are currently two solutions: (1) Change the adsorbate nitrogen to krypton gas, because the cross-sectional area of krypton gas molecules is much smaller than that of nitrogen molecules, so the adsorption capacity can be greatly increased for samples with the same specific surface area; (2) Try to modify the adsorption capacity The device may change static adsorption to flow adsorption, increase the sample volume, and thereby increase the adsorption capacity.