SIMULTANEOUS DETERMINATION OF MIXTURE OF VERY WEAK ACIDS OR BASES BY 2-DIMENSIONAL PH-TITRATION

A new method, two-dimensional pH-titration, for simultaneous determina tion of mixture of very weak acids or bases is proposed. Titration vol ume data matrix is measured at different fixed pH values. Principal co mponent regression is carried out to simultaneously determine every co mponent in the mixtures. The systematic deviations of pH measurement d o not affect the accuracy of determination results. The mixtures of p- chlorophenol and o-chlorophenol and the mixtures of citrate and tartra te are determined. The relative error is lower than 0.5% and 1%, respe ctively. Effects of the resolution Delta pK(a) and sampling interval D elta pH are studied. The relative error is lower than 1% when Delta pK (a) > 0.4 and Delta pH = 0.1.