Characterization of Fourier Transform Infrared, Cavity Ring-Down Spectroscopy, and Optical Feedback Cavity-Enhanced Absorption Spectroscopy Instruments for the Analysis of Ammonia in Biogas and Biomethane.

Novel traceable analytical methods and reference gas standards were developed for the detection of trace-level ammonia in biogas and biomethane. This work focused on an ammonia amount fraction at an upper limit level of 10 mg m (corresponding to approximately 14 μmol mol) specified in EN 16723-1:2016. The application of spectroscopic analytical methods, such as Fourier transform infrared spectroscopy, cavity ring-down spectroscopy, and optical feedback cavity-enhanced absorption spectroscopy, was investigated.

Gaseous reference standards of formaldehyde from trioxane.

We have developed a dynamic reference standard of gaseous formaldehyde based on diffusion of the sublimate of trioxane and thermal conversion to formaldehyde in the gas phase. We have also produced a gravimetric standard for formaldehyde in a nitrogen matrix, also by thermal conversion of the sublimate of trioxane. Analysis of the gravimetric standard with respect to the dynamic standard has confirmed the comparability of the static and dynamic gravimetric values.

Uncertainty estimation in chemical measurements: carbon dioxide determination at atmospheric concentration.

The present work deals with the evaluation of measurement uncertainty in the determination of carbon dioxide (CO2) concentration in atmosphere, given the high relevance of this greenhouse gas that influences earth climate. In order to carry out CO2 measurements, non dispersive infrared (NDIR) analysers are usually employed as they are stable and scarcely affected by interferences from other air components or pollutants. Typical uncertainty sources are the resolution of the analyser, its time drift and the contributions due to instrument calibration, which is required in order to produce traceable measurement results.

Stability of a NDIR analyser for CO2 at atmospheric concentration.

Carbon dioxide monitoring is significant in the environmental field since this gas plays an important role in the greenhouse effect. In order to determine CO2 concentration and to develop simulation models, it is necessary to carry out measurements which are accurate and comparable in time and space, i.e.