Surface pKa of octanoic, nonanoic, and decanoic fatty acids at the air–water interface: applications to atmospheric aerosol chemistry

文献情報

出版日 2017-08-08

DOI 10.1039/C7CP04527A

インパクトファクター 3.676

著者

Bethany A. Wellen, Evan A. Lach, Heather C. Allen

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要旨

There exists large uncertainty in the literature as to the pKa of medium-chain fatty acids at the air–water interface. Via surface tension titration, the surface-pKa values of octanoic (C8), nonanoic (C9), and decanoic (C10) fatty acids are determined to be 4.9, 5.8, and 6.4, respectively. The surface-pKa determined with surface tension differs from the bulk value obtained during a standard acid–base titration. Near the surface-pKa of the C8 and C9 systems, surface tension minima are observed and are attributed to the formation of surface-active acid–soap complexes. The direction of the titration is shown to affect the surface-pKa of the C9 system, as the value shifts to 5.2 with NaOH titrant due to a higher concentration of Na+ ions at pH values close to the surface-pKa. As the reactivity and climate-relevant properties of sea spray aerosols (SSA) are partially dictated by the charge and surface activity of the organics at the aerosol–atmosphere interface, the results presented here on SSA-identified C8–C10 fatty acids can be used to better predict the health and climate impact of particles with significant concentrations of medium-chain fatty acids.

掲載誌

Physical Chemistry Chemical Physics

CiteScore: 5.5

自己引用率: 10.3%

年間論文数: 3036

Physical Chemistry Chemical Physics (PCCP) is an international journal co-owned by 19 physical chemistry and physics societies from around the world. This journal publishes original, cutting-edge research in physical chemistry, chemical physics and biophysical chemistry. To be suitable for publication in PCCP, articles must include significant innovation and/or insight into physical chemistry; this is the most important criterion that reviewers and Editors will judge against when evaluating submissions. The journal has a broad scope and welcomes contributions spanning experiment, theory, computation and data science. Topical coverage includes spectroscopy, dynamics, kinetics, statistical mechanics, thermodynamics, electrochemistry, catalysis, surface science, quantum mechanics, quantum computing and machine learning. Interdisciplinary research areas such as polymers and soft matter, materials, nanoscience, energy, surfaces/interfaces, and biophysical chemistry are welcomed if they demonstrate significant innovation and/or insight into physical chemistry. Joined experimental/theoretical studies are particularly appreciated when complementary and based on up-to-date approaches.