Determination of partition coefficients and dissociation constants of neutral weak acid in single titration

Abstract

The three parameters, equivalent point or purity, dissociation constant and partition coefficient, were calculated applying multiple linear regression equation to simulated titration data by three computer programs (Excel®2007, Wessa (2009) and MINITAB®15) and all obtained results were compared. In many cases, analysis of simulated data yield inaccurate results, possibly due to programming algorithms. The two modified simple linear regression equations were derived for determination of equivalent point of titration and partition coefficient using titration data from dual phase titration. The two modified simple linear equations, together with Gran equation, can be employed to determine equivalent point or purity, dissociation constant and partition coefficient of weak monoprotic acid from one single titration experiment. The obtained parameters of five weak monoprotic acids, acetic acid, benzoic acid, 2-methoxybenzoic acid, salicylic acid and m-toluic acid, were determined using reference method and potentiometric methods. These results suggest that this method is effective and useful as its saving time.