Time-resolved ammonia measurement in vehicle exhaust
by Joachim Mohn, Anna-Maria Forss, Stefan Bruhlmann, Kerstin Zeyer, Roland Luscher, Lukas Emmenegger, Philippe Novak, Norbert Heeb
International Journal of Environment and Pollution (IJEP), Vol. 22, No. 3, 2004

Abstract: The objective of this study was to identify the influence of sampling and analytical approach on the quality of NH3 emission data of a gasoline-fuelled three-way catalyst vehicle. NH₃ concentration measurements have been performed in the tailpipe and in the diluted exhaust after a constant volume sampling (CVS) system during five different test cycles. Chemical ionisation mass spectrometry (CI-MS) and Fourier transform infrared spectroscopy (FTIR) were used to acquire ammonia concentrations in real-time. Independently, NH₃ emission rates were determined by continuous absorption of a flow-proportional sample of exhaust gas in diluted sulphuric acid and subsequent ion chromatography (IC). Ammonia emission rates ranged from 22–94 mg km^-1. The results of the three compared techniques are in good agreement. Furthermore, time-resolved ammonia emission profiles recorded by CI-MS and FTIR coincided with respect to emission levels as well as emission dynamics. However, in the dilution tunnel, severe ammonia adsorption was observed leading to long lasting memory effects or even analyte loss. Therefore, neither ammonia real-time emission data nor NH₃ emission rates should be acquired after a CVS system.

Online publication date: Tue, 19-Oct-2004

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