Miscibility of perfluorododecanoic acid with organic acids at the air-water interface

Field measurements have established that a significant percentage of atmospheric aerosol composition consists of organics. Perfluorinated compounds have been used in industry over the past 50 years, and recently, they have been detected in the atmosphere, environmental waters, the Arctic food chain, tissues of animals, and human blood. In general, fluorinated compounds are better surfactants than their hydrocarbon analogs. In this work, isotherms of perfluorododecanoic acid, stearic acid, and lauric acid were studied using a Langmuir-Blodgett trough. Isotherms of the pure and mixed films at varying concentrations were collected and characterized to determine their stability and miscibility. Our results indicate that perfluorododecanoic acid forms miscible films in mixtures with stearic and lauric acid. The impetus for this research was to better understand the heterogeneous chemistry of mixed films containing perfluorinated compounds. Consequences of these results for the fate of perfluorinated acids in the environment are discussed.