What materials are commonly used in gas sampling bags?

The gas sampling bag is mainly composed of film and valve: the part in contact with gas is also film and valve.

At present, there are three kinds of materials widely used: aluminum foil composite film, Teflon (polytetrafluoroethylene) film and Tedra (polytetrafluoroethylene); The common valves in China are: Teflon on-off valve, non-switching Teflon nozzle, polypropylene (PP) valve, ABS valve, metal valve or nozzle.

If PTFE and Tedra are recognized as acid-resistant, alkali-resistant and corrosion-resistant materials in terms of the stability of membrane materials, and their physical and chemical properties are relatively stable, then the background value of sampling bags made of these two materials is the lowest in terms of membrane materials. In addition, the gas sampling bag should be equipped with valves, of course, Teflon valves are better, because Teflon valves are designed at home and abroad, and the general sealing ring does not contact with gas samples.

The conclusion is: PTFE membrane+PTFE valve; Or Tedra membrane+Teflon valve, the background of the sampling bag is the lowest. Teflon membrane, Tedra membrane and Teflon valve are a perfect match, but they are expensive.

In order to use gas sampling bags correctly, we suggest following the following guidelines:

Before sampling

Unused bags are stored in a clean environment and placed in a sealed outer bag to prevent pollutants from being adsorbed.

Rinse with high purity nitrogen before use, and clean the sampling bag in advance.

The leakage rate shall not exceed 0.1"Hg/min.

Sampling period

Do not inflate the airbag more than 80%.

Make sure to connect the airbag with a clean PTFE tube.

Use vacuum box sampler to sample the sampling bag to avoid polluting the sampling pump.

A typical flow rate is 3 liters/minute.

After sampling

Because there is a risk that the sample will be adsorbed on the airbag, the airbag should be used once.

The storage time is usually less than 48 hours, unless the verification study proves that the sample has longer stability.

Avoid direct sunlight and keep it above 0℃ to prevent condensation.

Transport in rigid opaque containers to prevent the airbag from being punctured.