Collect. Czech. Chem. Commun. 1994, 59, 322-329

The Effect of Surfactants on the Acid-Base Behaviour of Methyl Red. Part II. A Spectrophotometric Comparison of the Effect of Triton X-100 and β-Cyclodextrin

Jana Jirasová, Jiří Bílý and Ludmila Čermáková

Department of Analytical Chemistry, Charles University, 128 43 Prague 2, Czech Republic


The effect of the non-ionogenic surfactant Triton X-100 (TX) and β-cyclodextrin (CD) on the absorption bands of methyl red was examined. The interactions of methyl red with the both substances were studied based on changes in the absorption curves after their resolution into Gaussian bands. The conditional dissociation constants of methyl red were determined at various concentrations of the additives (in the case of TX, both below and above its cmc value). At cTX = 0.06 mol l-1 the change in the conditional dissociation constant of methyl red was ∆pKa = -0.58 and at cCD = 6 mmol l-1 the ∆pKa value was identical.