The HD-C18 phase is best suited for separating highly hydrophobic small molecules with small structural differences - for example isomers. The density of C18 chains on the surface of the organosilica hybrid particles is higher than that of Scepter C18. As a result, molecules that can fit between the C18 chains due to their size experience more interactions than molecules whose molecular structure does not allow them to fit in, or only partially. This allows molecules with small structural differences to be separated more easily.