Abstract Number: 560 Working Group: Instrumentation and Methods
Abstract Transmission-mode analysis of Fourier Transform Infrared (FT-IR) spectroscopy of particulate matter (PM) collected on Teflon filters has provided chemically informative, quantitative analysis of PM in past studies. FT-IR analysis of solvent extracted fractions of PM has also provided qualitative information on organic PM composition separated by polarity (e.g., Polidori et al., doi:10.1080/02786820801958767, 2008; Chen et al., Environ. Sci. Tech., doi:10.1021/acs.est.5b05277, 2016), and also provides an alternative mode of analysis when direct transmission mode analysis is not possible on account of the optical characteristics of filter media. In this work, we evaluate methods for extraction and analysis of PM for organic matter to organic carbon (OM/OC) ratios by FT-IR in transmission and Attenuated Total Reflectance (ATR) modes. The extracted fraction is deposited onto a ZnSe support window (for transmission) or infrared element (for ATR). We compare three different methods for transfer of extracted solution: 1) deposition of a droplet onto the ZnSe crystal for analysis with FT-IR in transmission, 2) deposition of larger volumes (e.g., 500 microliters) onto a trough plate for analysis with ATR-FTIR and 3) electrospray deposition onto ZnSe crystal for FT-IR analysis. We report the development of an in-house electrospray device to improve uniformity of deposition, increase the rate of solvent evaporation, and advance our capability for extraction analysis. Evaluation of parameters for the electrospray deposition (e.g applied voltage, solvent choice, distance between needle and crystal, and solvent flowrate) are discussed in terms of reproducibility, rate of mass loading, and linearity of the resulting infrared spectra absorbance. Furthermore, we will present comparison of OM/OC ratios quantified from ambient aerosol collected onto quartz filters and parallel Teflon filters.