I. Principles for Selection and Use of Gas Sampling Bags

The correct selection and use of gas sampling bags are crucial to ensuring the accuracy and reliability of analytical data for gas samples.

For gas samples intended for collection and analysis, their physicochemical properties should be thoroughly understood. Based on the required analytical precision, determine the membrane material, interface type, and interface material of the gas sampling bag. The membrane of the gas sampling bag must not undergo chemical reactions with the gas sample. The adsorption and permeation of the membrane toward the gas sample should meet the analytical precision requirements, and the analytical data should exhibit excellent repeatability and stability. The selection of interface materials and connecting tube materials should also adhere to the above principles. The interface type should be determined based on the interface structure, physicochemical properties of the gas sample, analytical precision requirements, field conditions, and operational considerations. It should be noted that O-rings or rubber gaskets inside certain interfaces may be corroded by the gas sample in the sampling bag or contaminate the gas sample. For corrosive gases and high-precision sampling and analysis, it is recommended to use chromatography-specific silicone septa or chromatography-specific PTFE-coated silicone septa inside the sampling cap.