pellicular packing

in chromatography
https://doi.org/10.1351/goldbook.P04469
In this case the stationary phase forms a porous outer shell on an impermeable particle.
Source:
PAC, 1993, 65, 819. 'Nomenclature for chromatography (IUPAC Recommendations 1993)' on page 831 (https://doi.org/10.1351/pac199365040819)