AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Atmospheric Amine Measurements with CI-APi-TOF
TUIJA JOKINEN, Mikko Sipilä, Heikki Junninen, Mikael Ehn, Gustaf Lönn, Jani Hakala, Roy Lee III Mauldin, Tuukka Petäjä, Markku Kulmala, Douglas Worsnop, University of Helsinki
Abstract Number: 625 Working Group: Instrumentation and Methods
Abstract Nucleation is one of the main sources of cloud condensation nuclei (CCN) contributing up to 50% to the global CCN budget. The initial steps of nucleation require the presence of sulphuric acid (SA) but additional vapours are needed because SA does not nucleate itself. Ammonia and dimethylamine (DMA) are found from charged clusters formed by ion induced nucleation and the conclusion is that amines are plausible candidates for stabilizing neutral clusters. Even ppt levels of amines can be enough to account for atmospheric nucleation rates.
We present the first ambient amine measurements using a Chemical Ionization APi-TOF (CI-APi-TOF). We used a special inlet for charging and acetone for the chemical ionization. In this experiment acetone was ionized using a bipolar charger to create positively charged acetone ions and clusters. In the proton transfer reaction only compounds that have higher proton affinity than the reagent ions will get charged and detected by the APi-TOF.
The data analysis is still ongoing and these results are preliminary. We identified amine clusters by their exact masses and isotope patterns. Two signals have been identified to correspond to common aliphatic amines. These signals are C4H12N+ (DMA) and C6H16N+ (triethyl amine). We can also demonstrate SA concentration anti-correlating with the amine signals. During a nucleation event, when SA concentration reaches its maximum, we only see a minimum amine signal. This may indicate that amines are reacting and/or clustering with freshly forming SA molecules.
This setup has a few disadvantages that need to be further developed. First, one of the most interesting amine signals, trimethyl amine, is overlapped with the acetone isotope signal. Second the inlet design needs to be improved to consume less chemicals and the reagent ion may have to be changed before quantitative analysis of atmospheric amines can be done using the CI-APi-TOF.