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.
Source:
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)