Application of non-ionic solid sorbents (XAD resins) for the isolation and fractionation of water-soluble organic compounds from atmospheric aerosols

A detailed procedure using non-ionic macropourous XAD-8 and XAD-4 resins is presented for the isolation and fractionation of aerosol water-soluble organic compounds (WSOC) from aerosol samples. The procedure entails adsorption of WSOC fraction onto XAD-8 and XAD-4 resins, desalting of the adsorbed organic material with ultra-pure water, elution of the retained organic matter with 40% MeOH solution and freeze-drying. Due to resin's different properties and to certain hydrophobic/hydrophilic interactions between the resin polymers and the organic matter, two major fractions were obtained; namely the XAD-8 and the XAD-4 eluates. The XAD-8 eluate, which accounts for 55-60% of total aerosol WSOC, is represented by partially acidic compounds with significant hydrophobic moieties. The XAD-4 fraction holds few conjugated systems and a higher content of hydrophilic structures with low molecular size, and accounts for 9% of total WSOC. The isolated WSOC sub-fractions were nearly free from inorganic species, and successful recoveries of organic matter from the resins were accomplished. With this procedure the XAD-8 eluate yields a mixture representative of those WSOC that are highly conjugated compounds in atmospheric aerosols. It also allows a successful characterisation of the organic material by advanced analytical techniques without the interference of inorganic species present in the original sample of atmospheric particles.