The infrared fingerprint of the soluble fraction of atmospheric aerosol: towards the identification of functional groups influencing oxidative potential

The Fourier transform infrared (FTIR) spectroscopy allows the measurement of absorption peaks, due to vibrational transitions of individual chemical bonds, leading to the identification and quantification of main functional groups in a complex system. A number of investigations reporting the FTIR spectra of airborne aerosol samples have appeared in the last years (Coury and Dillner, 2009). In the attenuated total reflectance (ATR) mode, the sample is placed directly on a transparent crystal with a high refractive index, through which the IR beam is passed. The spectrum is then measured detecting the attenuation of the light reflected within the crystal and delivered to the detector. The path length depends solely on the penetration depth of the evanescent wave beyond the interface; therefore, the technique is suitable for analysing thin solid films with high sensitivity and repeatability. In this work, we have employed the ATR-FTIR technique for analysing thin solid films of particulate matter (PM) components, extracted from filter-deposited aerosol material, by solubilisation in deionized water. The goal was the identification of functional groups, soluble in aqueous biological fluids, able to influence the toxicological potential of airborne particles, in order to elucidate the relationships between PM chemical characteristics and human health effects.