Dielectric constant enrichment

The multilayered character of acetonitrile adsorption creates a pseudo-stationary phase of significant volume on the surface, which acts as a suitable phase for the ion accumulation. In the low organic concentration region (from 0 to 20 v/v% of acetonitrile), studied ions show significant deviation from the ideal retention behavior (decrease in ion retention with increase in acetonitrile composition) due to the formation of the acetonitrile layer, and significant adsorption of the chaotropic anions was observed. This creates an electrostatic potential on the surface in which there is an adsorbed acetonitrile layer, which provides an additional retentive force for the enhancement of the retention of protonated basic analytes. When the dielectric constant is lower than 42 [167], this favors the probability of ion pair formation in this organic enriched layer on top of the bonded phase. 

The model conceptualises the solution of (noble) gases on the microscopic level as cavities built by water molecules that trap individual (noble) gas atoms. The attracting forces between water and host increase with the atomic radius and the dielectric constant of the (noble) gas. In consequence, the intermolecular forces increase with molecular mass. This explains why the ratios of elemental noble gas concentrations in water at atmospheric equilibrium are enriched with respect to the atmospheric abundance in favor of the heavier noble gases. 

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