Atmospheric Chemistry Program Seminar

Methods for the quantification and identification of alkenes on indoor surfaces by Benjamin Deming,
ANYL 3rd year, Ziemann group
 
"Indoor surfaces can support organic films, which can act as sinks for semi-volatile organic compounds (SVOCs), reactors for condensed-phase reactions, sites of heterogeneous gas-condensed-phase reactions, and exposure routes for human health impacts. Although there have been some studies on indoor surface films, their size, composition, and chemistry are still uncertain. Additionally, the majority of studies investigating these films have been performed on impermeable surfaces, typically window glass. Painted surfaces, which tend to dominate by surface area, potentially differ from glass in several important ways, and are therefore an understudied aspect of indoor environments. Interior wall paint is normally composed of an organic binder and an inorganic filler, which may change the way films initially form as well as their subsequent growth. Film components may also absorb into paint and away from the surface, changing the composition of the film that remains. Oxidation indoors is largely driven by ozone and reactions with alkenes are therefore of particular interest. There are a number of sources unique to indoor environments which may contribute alkenes to surface films: cooking oils can have a high degree of unsaturation, many fragrances and cleaners contain terpene derivatives, and human beings constantly produce skin oil, which contains squalene and unsaturated fatty acids. To explore these areas of interest we characterized a method for quantitatively sampling the low-volatility, organic portion of a surface film using a surface wipe and developed a spectrophotometric method for quantifying nanomole quantities of alkenes. Samples were also derivatized, adding a readily ionizable group to non-conjugated double bonds, allowing for identification by positive-mode ESI-MS. Samples from neighboring glass and painted surfaces were collected from a variety of locations, including a classroom, graduate student offices, a bowling alley, a gym, and more. To investigate the effect of cooking on nearby surface concentrations we pan-fried three different cooking oils at high temperatures and analyzed the double bond content of the raw oil, cooked oil, and nearby surfaces. The effect of ongoing exposure to ozone on the alkene concentrations on the human envelope was explored by obtaining samples from the foreheads of volunteers at different times of the day. In a final experiment we studied the effect of using a terpene cleaner on measured surface concentrations. The results from this work should be useful to the modeling of indoor environments and help assess the importance of surfaces to indoor chemistry."