Spectrophotometric Determination of Conditional Acidity Constant of Some Sulfonephthalein Dyes as a Function of Anionic, Neutral and Cationic Surfactants Concentrations Using Rank Annihilation Factor Analysis

Abstract

Rank annihilation factor analysis (RAFA) is proposed to the spectrophotometric studies of acid-base
equilibrium of some sulfonephthalein dyes in the presence of sodium dodecyl sulfate (SDS), triton X100 (TX-100) and cetyltrimethylammonium bromide (CTAB). When the conditional acidity constant
(surfactant concentration dependent acidity constant) acts as an optimizing object, and simply is
combined with the pure spectrum of acidic or basic forms, the rank of original data matrix can be
reduced by one by annihilating the information of the acidic or basic spectrum from the original data
matrix. The residual standard deviation (R.S.D.) of residual matrix is regarded as the evaluation
function. Spectrophotometric studies of bromothymol blue, bromophenol blue and bromocresol green
in the presence of varying amounts of above surfactants are used as experimental model systems and
the amounts of conditional acidity constants are calculated. The conditional acidity constants decrease
by increasing of SDS and TX-100 concentrations for all three investigated dyes. But increasing of
CTAB concentration has different effects on the dissociation constants of three dyes.