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

Kobra Zarei, Morteza Atabati and Esmaeil Abdinasab

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RAFA; Conditional acidity constant; Sulfonephthalein dyes; TX-100; SDS


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 X-100 (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.