Abstract Number: 698 Working Group: Instrumentation and Methods
Abstract This work describes and evaluates the algorithm introduced by Russell et al. 2009 for apportionment and quantification of oxygenated (carbonyl and hydroxyl) functional groups in organic aerosol from Fourier Transform Infrared Spectroscopy (FTIR) analysis of the condensed phase. The procedure for spectra interpretation and quantitative analysis is described through the context of an algorithm in which contributions of background and analyte absorption to the infrared spectrum are apportioned by the superposition of lineshapes constrained by laboratory measurements. For the absorption profile of carboxylic COH, which is particularly broad, an average lineshape is extracted from profiles of a fatty acid series using a statistical decomposition method.
Our algorithm for quantifying carboxylic COOH is applied to a multifunctional compound, and to a multifunctional mixture with <30% average prediction error. The ketonic C=O in pinonic acid is detected by our method by the amount of carbonyl in molar excess of carboxylic COH, and estimated within 25% of actual values. Aldehydic compounds are observed to form diols in aqueous solution in agreement with expectations; excess carbonyl detected in atmospheric samples are also likely to be ketonic rather than aldehydic C=O. This algorithm has been applied to the analysis of ambient particles collected on Teflon substrates during field campaigns between 2006 and 2010. The reproducibility introduced through its implementation leads to improved precision in the FTIR measurements, and provides an explicit framework by which additional constraints can be used to reduce the uncertainty in this analysis technique.
Russell, L. M., Takahama, S., Liu, S., Hawkins, L. N., Covert, D. S., Quinn, P. K., Bates, T. S., 2009. Oxygenated fraction and mass of organic aerosol from direct emission and atmospheric processing measured on the R/V Ronald Brown during TEXAQS/GoMACCS 2006. Journal of Geophysical Research-Atmospheres 114, D00F05.