mass fraction of the packing material which is carbon. Usually taken as a guide to the extent of alkyl substitution on the surface. Usually reported as percentage carbon determined using elemental analysis.
PAC, 1997, 69, 1475. 'Classification and characterization of stationary phases for liquid chromatography: Part I. Descriptive terminology (IUPAC Recommendations 1997)' on page 1477 (https://doi.org/10.1351/pac199769071475)