10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Analysis of Solutions by Fourier Transform Infrared Spectroscopy by Electrospray Film Deposition
ANDREA ARANGIO, Christophe Delval, Giulia Ruggeri, Satoshi Takahama, EPFL
Abstract Number: 1216 Working Group: Instrumentation
Abstract Fourier transform infrared (FTIR) spectroscopy is a powerful technique that has been widely applied for functional group analysis and organic matter quantification in atmospheric aerosol particles. However, FTIR transmission spectroscopy of particles collected on Teflon filters render some regions of the infrared spectrum inaccessible due to interferences from the substrate. Additionally, significant background correction of spectra is required to account for the Teflon absorption and scattering to obtain the actual spectrum of the particulate matter sampled. Transmission analysis with FTIR is not applicable for particles collected on quartz-fiber filters because of the high IR-absorption of the quartz. To overcome the filter interferences and extend FTIR applicability, solvent extraction protocols are typically applied to analyse soluble fractions of particulate matter.
FTIR analysis of filter extracts is also complicated by the significant IR-absorption of solvents but these issues can be circumvented by applying solvent-elimination techniques. In these approaches, the solvent is evaporated while the separated compounds are immobilised on a substrate prior to the collection of the FTIR spectrum.
In this work we present a rapid solvent-elimination method based on electrospray technique to isolate analytes for chemical characterization. Extracted solutions from filters are purged through an electrified needle to generate a spray in which micro-droplets allow fast solvent evaporation. The resulting solutes are deposited onto a grounded Internal Reflection Element (IRE) to apply Attenuated Total Reflectance - FTIR (ATR-FTIR) spectroscopy. ATR-FTIR is a sensitive technique with capability to analyse submicrogram quantities of analytes and is therefore selected to obtain the maximum signal-to-noise ratio. Several parameters that affect the electrospray film deposition, together with the linearity of the response over a wide mass range are investigated for volatile and non-volatile organic compounds and inorganic salts. The method is highly reproducible and the instrumental limit of detection is as low as 250 ng.