Preparation of standard gas with special properties

1. Preparation of lively standard gas

Some gases are particularly active in nature and easily react with oxygen and water packaging container materials to cause changes in concentration. These gases have been prepared in small amounts using ampoules, saturated vapor pressure and other methods in the past, and they are not suitable for long-distance transportation and long-term storage. In the 1980s, the United States NIST and some special gas companies such as SCOTT, etc., developed the inner coating technology for steel cylinders through experiments. This technology effectively prevents the reactive gas from reacting with the inner wall of the steel cylinder, which increases the stability of the gas, but the stability of the gas is limited to half a year, and the longest is no more than one year. The storage time is shorter when the concentration is low, and this method The prepared standard gas does not form the value transmission and traceability.

2. Preparation of volatile organic compound standard gas

Volatile organic compounds are an important indicator for studying indoor air pollution. In the past, these standard gases were prepared by permeation or diffusion methods, and standard gases of different concentrations were obtained by changing the temperature and the geometry of the diffusion tube. As early as the early 1980s, the United States developed a method for accurately weighing small amounts of liquid with capillary tubes. At present, there are as many as 39 traceable NIST-valued VOCs standard gases.

In recent years, with the introduction and digestion of world advanced gas distribution technology, coupled with the efforts of several generations of scientific research workers in China, China has made rapid development in the preparation of standard gases, and the preparation of gases in the range of constant and semi-trace concentration has formed a measurement. The traceability system can be compared with international standard materials.