Prediction of retention factors of phenolic and nitrogen-containing compounds in reversed-phase liquid chromatography based on logP and pKa obtained by computational chemical calculation

The new logP values (NlogP) of phenolic and nitrogen-containing compounds based on the modified CAChe(TM) MOPAC calculation improved the correlation coefficient with measured logP values (MlogP) to 0.950 from 0.662 (n = 87). The best correlation coefficient was obtained between retention factors of their molecular form and NlogP values among NlogP, CAChe logP, MOPAC-BlogP, Rekker's logP, Hansch's logP, and MlogP. Correlation coefficients were 0.880 (n = 50) for phenolic compounds and 0.900 (n = 48) for nitrogen-containing compounds. The correlation coefficients between predicted and measured maximum retention factors were 0.883 (n = 50) for phenolic compounds and 0.891 (n = 48) for nitrogen-containing compounds. Addition of pka values predicted by partial charges of atoms calculated using CAChe(TM) MOPAC to NlogP values could predict their retention factors in eluents at given pH. The correlation coefficient between predicted and measured retention factors of phenolic compounds at pH 8.49 was 0.927 (n = 20), and that of nitrogen-containing compounds at pH 4.0 was 0.833 (n = 45).