Simple Preparation of Calibration Curves for Oxygen and Nitrogen Using Air as a Standard Gas

User Benefits

- Simple preparation of multipoint calibration curves for the low concentration regions of O₂ and N₂ is possible without dilution of standard gases. - Low cost analysis is possible by using air as a substitute standard gas. - Use of an autoinjector enables high injection accuracy in measurements.

Introduction

When analyzing oxygen (O₂) and nitrogen (N₂), which exist at high concentrations in the atmosphere, the effect of contamination by air must be avoided as far as possible. Particularly when preparing calibration curves for low concentration regions, it is necessary to prepare cylinders of the standard gases and prevent contamination by air from the atmosphere during sample injection. Although a gas sampler is generally used, consumption of the standard gases is large because the sample injection lines must be purged sufficiently with the standard gas before measurements. Moreover, use of a multipoint calibration curve is desirable, but the cost of preparing multiple standard gas cylinders with different gas concentrations would be prohibitive. Although dilution of the standard gas by the analyst is possible, it is extremely difficult to avoid air leaks when preparing diluted gases. Air contains about 21 % O₂ and 78 % N₂, and these concentrations are considered to be comparatively stable. The cost of quantitative analyses of O₂ and N₂ can be reduced if air is used as a simple standard gas. This Application News introduces the results of a study of a simple method for preparation of multipoint calibration curves for O₂ and N₂ in the low concentration region without dilution of the standard gases by using air as a substitute standard gas and varying the air injection rate.

June 15, 2023 GMT