Separation selectivity of some phenolic acids in RP HPLC systems with binary mobile phase comprised various modifiers

Retention of phenolic acid has been correlated for reversed-phase high-performance liquid chromatography systems with different binary mobile phases containing methanol, acetonitrile or tetrahydrofuran as modifiers and buffer at pH 3.0, 4.6 and 5.0. The changes of separation selectivity of solutes, when one modifier is replaced by another in the eluent, has been explained taking into consideration molecular interactions of the solutes with components of the stationary phase region, i.e. extracted modifier, and ordering of the stationary phase by the modifier.