Method for Measuring NOx Concentrations in Small Quantities of Sample Gas

This study attempted to measure the concentration of NOx in a small gas sample, with a chromatograph equipped with a flame ionization detector (FID), by reacting NOx as an organic gas with alcohol and converting it into esters of nitrous acid having organic carbon atoms.

It was found that since the FID is highly sensitive to hydrocarbons the measurements were difficult with high concentrations of hydrocarbon components with low boiling points at the elution position of the esters of nitrous acid. To resolve this a gas chromatograph equipped with an electron capture detector (ECD), which is selectively sensitive to esters of nitrous acid and not sensitive to hydrocarbon components with low boiling points was used.