Analysis of Uncertainty of Standard Gas Component Value

Gas standard samples and gas standard materials (hereinafter referred to as standard gases) as a kind of physical standards and measurement standards are widely used in scientific research, environmental testing, medical and health, petrochemicals, fertilizers, electric power, coal, metallurgy, machinery and other national economies Various fields. Standard gases have played an extremely important role in calibrating instruments and meters, evaluating measurement methods, transmitting and arbitrating measurement standards, and effectively implementing gas standards.

      The production and use of standard gases in our country are large and wide. However, the components of these standard gases are often not standard, and the market is extremely chaotic. Standard gases with the same component content (especially those with oxygen and nitrogen components) Gas) is used to compare the value, and the difference of the comparison data is more than double.

      The uncertainty of the standard gas volume value introduced in the preparation process is mainly composed of the system air tightness and weighing error of the gas cylinder processing and preparation process. The preparation uncertainty can be reduced by improving the precision of the gas distribution equipment and strict preparation procedures. Elimination, such as the use of high-precision weighing equipment, high-performance gas distribution device, gas cylinder processing system that meets the requirements, strict gas distribution process and laboratory conditions, etc.

      The uncertainty of the prepared standard gas value caused by the analysis process mainly comes from the following aspects: one is that the standard gas value used by the analyzer is not accurate; the other is that the carrier gas system of the analytical instrument cannot guarantee the reference zero point gas. The value is absolutely zero; the third is that the sensitivity of the analytical instrument cannot reach the detection accuracy it should, and the detection limit of many analytical instruments is above 0.1*10-6; the fourth is that 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. When 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 component to solve the problem of accurate and reliable standard gas required by our country, and calculate the absolute component value of the self-made standard gas.