Dynamic chromatography specific surface principle and test process - Database & Sql Blog Articles

Continuous flow chromatography is a method for determining the amount of nitrogen adsorption on the surface of a powder by using a thermal conductivity detector in a gas chromatograph, that is, nitrogen is used as the adsorbate and helium is used as the carrier gas, and the two gases are mixed in a specified ratio to reach a certain level. Nitrogen partial pressure, let this gas flow through the sample tube containing the powder sample, when the sample tube is placed at the liquid nitrogen temperature, the nitrogen is physically adsorbed on the surface of the sample, and the helium gas is not adsorbed, then the concentration of nitrogen in the gas stream Reducing, an electrical signal is generated at the output of the thermal conductivity detector to form a so-called nitrogen adsorption peak. When the sample tube returns to room temperature, the adsorbed nitrogen on the surface of the sample is completely desorbed to form a desorption peak. The size of the peak area of ​​the absorption (desorption) is proportional to the amount of nitrogen adsorption on the surface of the sample. In the dynamic method, the sample is in dynamic equilibrium with the nitrogen-containing gas flowing on the surface. Due to the low gas flow rate, it can be considered to be close to the equilibrium state. By adjusting the ratio of nitrogen to helium to change the partial pressure of nitrogen, the BET ratio can be realized. Surface and pore size distribution testing.