Every new method for sampling complex molecules from liquids and solids into the gas phase has fueled the expanding application of mass spectrometry to molecular biology and other fields of science. Recently developed, field induced droplet ionization (FIDI), combined with mass spectrometric (MS) sampling, holds promise for a broad spectrum of applications. FIDI-MS is based on the physics of nanoliter droplets in time dependent electric fields, leading to formation of dual Taylor cones from which streams of positively and negatively charged submicron droplets are emitted in opposite directions, forming what is essentially a dual electrospray ion source. In multi-component systems ionic species with high surface activity are detected with high sensitivity, along with molecular clusters indicative of specific ion pair interactions and molecular aggregation at the air-water interface. The air-water interface represents one of the most ubiquitous chemical environments in nature, present on the surface of oceans and lakes, on atmospheric aerosols, and even in the human respiratory system. Yet in spite of their prevalence, chemical reactions occurring at these interfaces remain poorly characterized. FIDI-MS has proven itself to be ideally suited for such studies. Several examples of these investigations will be presented, including organic reaction mechanisms involving acid and base catalysis, atmospheric aerosol chemistry, and processes that involve biological interfaces such as the pulmonary surfactant layer, where we have unraveled the myriad chemical and physical processes associated with oxidants such as ozone interacting with lipids and proteins in this complex interfacial environment. Theoretical studies involving state of the art molecular dynamics and quantum chemical calculations play an important role in in these investigations. Several new approaches demonstrating selective sampling of complex molecular species from planar liquid surfaces will also be discussed.

Field induced droplet ionization:  Investigations of complex chemical reactions at the air-water interface employing mass spectrometry

248th National Meeting (2014)

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