Analytical Accuracy of Standard Gases

1. General rules for standard gas preparation 

The development process of the standard gas can be divided into four parts: the purity analysis of the raw material gas; the preparation of the component pressure by weighing method; the calibration of high-precision analytical methods such as gas chromatography and chemiluminescence; the performance inspection and packaging conditions. The developer and producer of standard gas should ensure that there are detailed technical information and reproducible descriptive documents for the standard gas to guide the preparation process, and ensure the normal use of the equipment required for preparation. All preparation processes should be carried out in accordance with predetermined preparation procedures and controlled to avoid influence from outsiders or the environment.

2. Purity analysis of raw material gas prepared from standard gas

The standard gas has high requirements on the accuracy of the provided characteristic values, and the quality of the raw material gas should be controlled before preparation. Dilution gas high-purity nitrogen, in which the content of related impurities CO, CH4, CO2 must be accurately analyzed and determined. Obviously, in the preparation process of standard gas, the contents of CO, CH4 and CO2 in nitrogen will all be introduced into the standard gas and directly affect the result of the determination, especially when the standard gas with lower content is prepared, the impact is more prominent. . The purity analysis of the raw gas is a basic research work, which directly affects the determination result of the weighing method. The analysis of the feed gas needs to solve three problems, namely the main content, the content of the components to be prepared in the dilution gas, and the content of the components that interfere with the components to be prepared. This requirement is quite demanding, which inevitably leads to the research on gas analysis technology and purification technology. From this point of view, in the standard gas preparation process, the requirements for analysis technology and purification technology are quite high.

When the raw material gas required for the preparation cannot meet the production requirements of the standard gas, it should be repurified to ensure the effectiveness of the above preparation process and operation process.