concave isotherm

in chromatography
https://doi.org/10.1351/goldbook.CT06938
Distribution isotherm, the slope of which is continuously increasing.
Note:
The resulting chromatographic peak is fronting. In gas-liquid chromatography, overloading often results in a concave isotherm.
Source:
PAC, 1996, 68, 1591. (Nomenclature for non-linear chromatography (IUPAC Recommendations 1996)) on page 1593 [Terms] [Paper]