AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Resolving Complex Hydrocarbon Mixtures Using Gas Chromatography Mass Spectrometry with Soft Ionization
ARTHUR CHAN, Farhana Hoque, Aviv Amirav, University of Toronto
Abstract Number: 138 Working Group: Aerosol Chemistry
Abstract Emissions from petrogenic sources often contain many hydrocarbon isomers that are difficult to resolve, but understanding their molecular structure is crucial for predicting the atmospheric reactivities and aerosol formation from these sources. Recent developments in soft ionization mass spectrometry has allowed for classifying linear and branched alkanes, cycloalkanes, alkenes and aromatics, but the technique requires use of synchrotron radiation. In this work, we describe a new approach using a laboratory-based soft ionization technique to achieve the speciation. Using supersonic molecular beam for the coupling of GC and MS, electron impact ionization is carried out at low sample compounds internal temperatures, thereby enhancing their molecular ion signals and structurally informative high mass fragments. The molecular ion signal is shown to be constant at ~30% of the total ion count for n-alkanes ranging from C8 to C40, making it straightforward to quantify a wide range of volatilities. Using authentic standards, we are able to achieve more detailed understanding of molecular structures for more accurate atmospheric modeling. We are also able to lower the elution temperature of the GC column while maintaining isomer resolution. This allows us to study the composition of thermally labile compounds and high molecular weight compounds. Both of these types of compounds are prevalent in organic aerosols, but current techniques are unable to comprehensively speciate these compounds. This new approach is demonstrated on complex organic mixtures, such as diesel fuel and ambient organic aerosol samples.