Influence of variation in mobile phase pH and solute pKa with the change of organic modifier fraction on QSRRs of hydrophobicity and RP-HPLC retention of weakly acidic compounds

► (Mobile phase pH-solute pKa) is independent of change of organic modifier fraction. ► The variation in pH and pKa does not affect QSRR of log Kow″ and log kw for weak acids. ► The rigorous pH and pKa measurement in relative studies is not compulsively necessary.