Separation and detection of aqueous atmospheric aerosol mimics
using supercritical fluid chromatography–mass spectrometry
Abstract. Atmospheric particles contain thousands of compounds with many different functional groups and a wide range of polarities. Typical separation methods for aqueous atmospheric systems include reverse-phase liquid chromatography or derivatization of the analytes of interest followed by gas chromatography. These methods can be time-consuming and do not easily separate highly polar aqueous molecules. This study uses supercritical fluid chromatography-mass spectrometry to separate the methylglyoxal-ammonium sulfate reaction mixture as a proxy for aqueous atmospheric aerosol mimics. Several column compositions, mobile phase modifiers, and column temperatures were examined to determine their effect on separation and the optimum conditions for separation in a minimal amount of time and sample preparation. Polar columns such as the Viridis UPC2 BEH column combined with a mobile phase gradient of carbon dioxide and methanol provided the best separation of compounds in the mixture. This separation method can be extended to analyze other aqueous atmospheric systems, including the mixtures of other aldehydes or organic acids with ammonium or small amines.