Determination of sugar compounds in atmospheric aerosols by liquid chromatography combined with positive electrospray ionization mass spectrometry

Abstract

We here report a method for the determination of sugar compounds of known presence in atmospheric aerosols using liquid chromatography (LC) combined with positive electrospray ionization mass spectrometry (MS). The target analytes include C 3–C 6 monosaccharide alcohols (glycerol, erythritol, xylitol, mannitol), C 5–C 6 monosaccharides (xylose, glucose, and levoglucosan), a disaccharide (sucrose), and a trisaccharide (melezitose). A mobile phase consisting of 20% 10 mM aqueous ammonium acetate, 8% methanol, and 72% water was found to provide abundant [M + NH 4] + adduct ions when coupled with electrospray ionization. Use of a polymer-based amino analytical column resolved the target compounds from the bulk solvent and provided limited separation among the target compounds. The target analytes were quantified using their [M + NH 4] + ions. Sample pretreatment was greatly simplified in comparison with the more commonly used gas chromatographic methods. It involved extraction of aerosol filters in methanol, evaporation of the solvent, and reconstitution with 5 mM ammonium acetate in water prior to the LC–MS analysis. The analyte recoveries were measured at the levels of 100, 500 and 1000 μg/L to be in the range of 78–102%, 94–112%, and 92–110%, respectively. The detection limits were lower than 10 pmol/injection for the tested target compounds except for xylose. Xylose had a detection limit of 95 pmol/injection. The method was applied to analyze 30 atmospheric aerosol samples to demonstrate its feasibility. The LC–MS method made possible the detection of trisaccharides as aerosol constituents for the first time.