EFFECT OF INORGANIC SALT CONCENTRATION ON THE RETENTION VALUE IN REVERSED PHASE ION-PAIR LIQUID-CHROMATOGRAPHY

Thermodynamic and numerical treatments have been combined with Gouy-Chapman theory were to show that the effect of the salt concentration on the capacity factor in reversed-phase ion-pair liquid chromatography (RP-IPC) can be expressed as lnk' = A + BlnC(s). The parameter B is related to the charge number of the solute, and the parameter A is determined by both electrostatic and non-electrostatic interaction, and can be linearly correlated with logarithm of the capacity factor in RP-HPLC for the solute with one negative charge. It also has been observed that the electrostatic interaction is reduced with increasing salt concentration in RP-IPC, and this effect is more remarkable for solutes with more than the one negative charge of sulphonic acids.