Analysis of Uncertainty of Standard Gas Component Value

Gas standard samples and gas standard substances (hereinafter referred to as standard gases), as a physical standard and measurement benchmark, are widely used in scientific research, environmental testing, medical and health, petrochemical, chemical fertilizer, electric power, coal, metallurgy, machinery and other national economies. of various fields. Standard gas has played an extremely important role in calibrating instruments and meters, evaluating measurement methods, transferring measurement standards and arbitrating values, and effectively implementing gas standards.

      The production and use of standard gases in our country is extensive, but these standard gases as benchmarks often have non-standard component values, and the market is extremely chaotic. Standard gases with the same component content (especially the standard gas containing oxygen and nitrogen components It often happens that the comparison data are more than doubled.

      The uncertainty of the standard gas quantity introduced in the preparation process is mainly composed of the system air tightness and weighing error in the gas cylinder handling and preparation process. Eliminate, for example, the use of high-precision weighing equipment, high-performance gas distribution devices, gas cylinder handling systems that meet requirements, strict gas distribution processes and laboratory conditions.

      The uncertainty of the prepared standard gas value caused by the analysis process mainly comes from the following aspects: First, the standard gas value used by the analyzer is inaccurate; second, the carrier gas system of the analytical instrument cannot guarantee the reference zero point gas. The value is absolute zero; third, the sensitivity of the analytical instrument cannot reach the due detection accuracy, and the detection limit of many analytical instruments is above 0.1*10-6; fourth, the reproducibility of the analytical instrument is not ideal.

      Therefore, it is necessary to establish a mathematical method to reduce or even eliminate the uncertainty of the standard gas component value caused by the analysis process. In the case where the uncertainty caused by the packaging container and the preparation process can be eliminated or determined, the mathematical method Calculate the absolute value of the prepared standard components to solve the problem of accurate and reliable standard gas in my country, and calculate the absolute value of the components for the self-made standard gas.