Determination of the dissociation constants of basic compounds by reversed-phase high performance liquid chromatography on C12-zirconia
Zhang, Q.; Zhang, W.; Li, T.; Zhang, Y.
Se Pu 23(5): 551-554
The high performance liquid chromatographic (HPLC) behavior of aromatic amines and pyridine derivatives was studied on a new reversed-phase stationary phase, C12-alkyl-modifled zirconia. The effects of mobile phase variables such as methanol content and pH were investigated. The results showed that the stationary phase was stable in the mobile phase with a pH range of 2 - 12. It was found that on the new stationary phase the bases demonstrated the "traditional" behavior of retention due to their hydrophobicity. The retention factors of these basic compounds on the stationary phase increased rapidly with pH from pH 2 -7, and then increased slowly until reaching a constant value. The dissociation constants (pKa) of 13 basic compounds were determined based on the relationship between their retention factors and the pH of mobile phase. Compared with references, the errors of the pKa values obtained by this HPLC method were within 0.35 pH units.