Applications of Liquid Chromatographic Techniques in the Chemical Characterization of Atmospheric Aerosols.

This paper presents a comprehensive literature review on liquid chromatography (LC) techniques, singular and/or in tandem with mass spectrometry (MS), applied to identify and quantify inorganic and organic chemical constituents in atmospheric aerosols. Significant contributions in the field of aerosol chemical composition, obtained either by field measurements or laboratory investigations, are also highlighted. The two major LC techniques that have been used to date to identify aerosol chemical constituents are ionic chromatography (IC) and high performance liquid chromatography (HPLC). They have been used more often in off-line than in on-line mode and both of them can be coupled with several types of mass spectrometry (MS). The two techniques seem to be suitable to obtain information on water-soluble inorganic and organic ions with low molecular weight (IC) or on organic compounds with higher molecular mass (HPLC). LC-MS with electrospray ionization is among the most powerful LC techniques to elucidate possible major contributors to the so-called "unidentified substances" fraction, and it is often reported in studies aimed to investigate the chemical composition of the aerosols. The information generated by liquid chromatography, especially related to different organic compounds into the aerosol particles, helped to elucidate some reaction pathways or improve some postulated mechanisms that may be responsible for the formation of secondary organic aerosols (SOA). However, despite the efforts made to elucidate the aerosols chemical composition, a significant part still remains highly unclear. It is expected that new studies carried out by using complementary analytical techniques will help answering such questions, but further development is needed to make such techniques applicable to large-scale analysis all over the world.