c1d6df67_C18s_Are_the_Same_Aren_t_They___2
[0] H [2] 
Hydrophobicity. A measure of the ability of the stationary phase to retain hydrophobic compounds. Traditionally ‘carbon loading’ was used as a measure of this parameter, but this took no account of several key effects (e.g. efficiency of ligand bonding process, ligand accessibility / performance and the degree / type of endcapping used. The PQRI ‘H’ value provides a far more quantifiable practical value to this critical feature. ‘H’ gives a measure of retention, but has only a minor effect on selectivity.
All HPLC C18s Are the Same Aren’t They?
2