Nebulization of Microliter-sized Environmental Samples: Aerosol Mass Spectrometry as an Offline Analytical Technique.

Abstract:

The Aerodyne Aerosol Mass Spectrometer (AMS) provides detailed information on the chemical composition of aerosol particulate matter with high time resolution. Traditionally, the AMS inlet samples directly from the air, but, nebulization of aqueous samples can also be used to produce aerosols for analysis with the AMS. Typical nebulizers require tens to hundreds of milliliters of solution, limiting this technique to large samples. Here, we demonstrate a micro-nebulizer that requires only small volumes (tens of microliters) of sample for chemical analysis with an AMS. With this technique, ultra-sonic vibrations are passed through a water reservoir. Samples loaded onto a thin film stretched over this reservoir are nebulized and transferred to the AMS with a carrier flow of clean air. We characterize this technique by exploring the elemental ratios, aerosol component ratios, and mass spectra for standards and filters. We also compare AMS data collected using standard on-line techniques with our offline analysis, demonstrating the applicability to filter samples collected from field sites and chamber studies. This technique is especially promising for the analysis of small environmental samples, such as filters collected in remote locations and rainwater samples.