Measurement of CO amount fractions using a pulsed quantum-cascade laser operated in the intrapulse mode

Abstract

Carbon monoxide (CO) is an important molecule for environmental monitoring, industrial process control, and a biomarker in exhaled human breath. Obtaining reliable and traceable data is indispensable. We employed direct absorption spectroscopy-based absolute amount fraction measurements of CO in a gravimetrically prepared gas mixture. A quantum-cascade laser operated in the intrapulse mode was used to probe the P(1) line of CO at 2139.4 cm−1. The spectrometrically determined CO amount fraction agrees perfectly with the gravimetric reference value. We focused on the method, the uncertainty analysis of the spectrometry-based data retrieval and the respective traceability of input parameters to the SI. An uncertainty budget is presented. Our reproducibility is better than 1%. The relative deviation of the spectrometric CO amount fractions from the gravimetric reference value reads minus 1.8%, which is covered by a 4% relative expanded uncertainty of single measurements (k=2).