c1d6df67_C18s_Are_the_Same_Aren_t_They___2
[0] A [2] 
Hydrogen Bond Acidity. Generally a desirable feature that gives a level of secondary interaction via low activity silanol groups on the support surface. This influences selectivity, particularly with retention of weakly basic molecules without excessive peak tailing. Many phases with high A values provide the ability to use 100% aqueous mobile phases.
All HPLC C18s Are the Same Aren’t They?
2