American Association for Aerosol Research - Abstract Submission

AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA

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Chemical Analysis of Microliter-sized Liquid Samples Using Ultrasonic Nebulization and Aerosol Mass Spectrometry

KELSEY BOULANGER, Eben Cross, James Hunter, Anthony Carrasquillo, Manjula Canagaratna, John Jayne, Philip Croteau, Jesse Kroll, MIT

     Abstract Number: 388
     Working Group: Instrumentation and Methods

Abstract
Aerosol mass spectrometry allows for detailed characterization of the chemical composition of organic species dissolved in liquid samples. However, traditional aerosol atomization typically requires liquid volumes of tens to hundreds of milliliters, which excludes many environmental samples. Here we demonstrate a nebulization technique whereby small volumes, on the order of ten microliters, are aerosolized and sent into an Aerodyne Aerosol Mass Spectrometer (AMS) for highly time- and mass-resolved chemical analysis. This technique passes ultrasonic vibrations through a thin film on top of a liquid reservoir, leading to the nebulization of liquid droplets placed on the film and significantly reducing the liquid volume traditionally necessary for AMS analysis. We present results from a variety of standards, including solutions of ammonium nitrate, ammonium sulfate, and various organic compounds, and compare aerosol species ratios, elemental ratios, and mass spectra to those obtained through conventional atomization. We examine the effects of sample concentration, volume, and airflow on the mass spectra as well as the total mass spectrometric signal and linearity. We also demonstrate the applicability to environmental samples using filter extracts from chamber secondary organic aerosol (SOA) experiments and comparing to online direct AMS measurements of aerosol composition. This is a promising technique for obtaining mass spectra of samples previously considered too small for AMS analysis, making it a viable option for the chemical characterization of environmental samples and other small-volume analytes.