Measurements of Low-Molecular-Mass Carboxylic Acids in Atmospheric Aerosols by Capillary Electrophoresis

Capillary electrophoresis (CE) methods for the determination of low-molecular-mass (LMM) carboxylic acids in airborne particular matter have been developed. The separations of 22 LMM carboxylic acids, including acids derived from the oxidation of biogenic hydrocarbons, are performed using a background electrolyte consisting of 3.0mM 2,6-naphthalenedicarboxylic acid and 18.0mM 2,2-bis (hydroxymethyl)-2,2',2"-nitrilotriethanol (Bis-tris) in 16% (v/v) 1-propanol within 10 min. Using a combination of a buffer mixed with an organic solvent and electroosmotic flow modifier, a minimum of peak overlaps is achieved with migration time variation of less than 1% and peak area ratio (relative to an internal standard) variation of less than 5% within 1 day. The detection limits for the aliphatic LMM acids that can be determined by this method are in the range of 30-140 micro g/L. Furthermore, a simple method for efficient extraction of LMM organic acids from particulate atmospheric matter collected on quartz fiber filters using high-volume samplers is developed. Combining the extraction procedure with a reduction of the extract to approximately 0.2 mL allows for the measurement of LLM in atmospheric particulate organic matter at concentrations well below 1 ng.m(-3). Repeat analysis of filters collected in tunnels, urban, suburban, and forested areas demonstrate that the procedure allows for measurements of aliphatic and aromatic LMM acids within a variability of 10-25%.