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Real-Time, Semi-Automated Fluorescent Measurement of the Airway Surface Liquid pH of Primary Human Airway Epithelial Cells
Published on: June 13, 2019
Experimental anion affinities for the air/water interface.
Jie Cheng1, Chad D Vecitis, M R Hoffmann
1W. M. Keck Laboratories, California Institute of Technology, Pasadena, California 91125, USA.
The Journal of Physical Chemistry. B
|December 22, 2006
Summary
Anion affinities at the water surface are influenced by ion size and hydration. Surfactants and pH changes alter these affinities, revealing insights into interfacial ion behavior and the Hofmeister effect.
Area of Science:
- Physical Chemistry
- Surface Science
- Analytical Chemistry
Background:
- Understanding interfacial anion behavior is crucial for various chemical and environmental processes.
- The Hofmeister effect describes how ions influence the properties of aqueous solutions.
Purpose of the Study:
- To quantify anion affinities at the aerial interface of aqueous solutions.
- To investigate the influence of surfactants and pH on interfacial anion behavior.
- To elucidate the relationship between anion properties and their interfacial affinities.
Main Methods:
- Electrospray ionization mass spectrometry (ESI-MS) was used to determine anion affinities.
- Fissioning nanodroplets were analyzed to study ion ejection from the surface.
- Various anions (Br-, NO3-, I-, SCN-, BF4-, ClO4-) and surfactants were employed.
Main Results:
- Anion affinities (gammaX-) correlate exponentially with anionic radii and dehydration free energies.
- BF4-, a weakly hydrated anion, exhibited a high interfacial affinity.
- Non-ionic surfactants altered affinities selectively, while cetyltrimethyl ammonium enhanced affinities for smaller anions.
- Lowering pH also influenced interfacial anion affinities, with dodecyl sulfate showing minimal effect.
Conclusions:
- The observed Hofmeister correlation (ln gammaX- proportional to -dGX-) supports the role of permittivity depression in the interfacial layer.
- Least hydrated ions optimally depress the permittivity of the drier interfacial layer, increasing their affinity.
- Interfacial ion-ion interactions significantly impact anion affinities in environmental aqueous media.
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