AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Direct Surface Analysis of Size- and Time- Resolved Organic Aerosol
STEPHEN FULLER, Markus Kalberer, Yongjing Zhao, Anthony Wexler, University of Cambridge
Abstract Number: 37 Working Group: Instrumentation and Methods
Abstract Ambient aerosol particles have been shown to have significant health and climate implications. Studies of the chemical composition of aerosol particles are important to establish the mechanisms of their reactivity. However the aerosol composition, especially the organic fraction is highly variable with both time and the particle size fraction concerned. Combining a rotating-drum impactor with Liquid Extraction Surface Analysis (LESA) - mass spectrometry allowed the study of separate size fractions collected over a 2-week period in May 2011 from a dairy farm in California to be analysed with a 40-minute time resolution using a high-resolution mass spectrometer for organic species identification.
LESA is a mode of operation of the electrospray NanoMate source (Advion) for mass spectrometers. A small amount of solvent is dispensed with a pipette tip on the surface of the sample; the micro liquid junction is maintained to allow analytes present on the surface of the sample to dissolve. The droplet is then aspirated and sprayed via an infusion method utilising the chip based electrospray ionsation. An ultra-high-resolution mass spectrometer was used determine the molecular formulae of the organic compounds found during the sampling period. The organic composition of particles in the two size fractions 2.5-1.1 and 0.3-0.09 micro-meters were investigated. The smaller size fraction was found to have higher nitrogen content, while the larger fraction higher oxygen content. The high time resolution achieved with the LESA technique allowed performing correlation analyses of the intensity variations for groups of compounds over the sampling period and groups of compounds with potentially the same source could be identified. This demonstrates that the combination of the RDI and LESA can be used for semi-quantitative analysis of organic components in ambient samples, with a high time resolution.