The effect of anionic and cationic surfactants on indicators and measurement of dissociation constants with two different methods.

The effects of cationic cetyltrimethylammonium bromide (CTAB), hexadecylpyridinum chloride (HDPC) and anionic sodium dodecylsulphate (SDS) surfactants on dissociation constants and transition intervals of methyl red, methyl orange and cresol red were studied spectrophotometrically. The results show that all studied indicators strongly interacted with cationic micelles (CTAB and HDPC). In the case of methyl red, relatively strong interaction with anionic surfactant (SDS) was obtained. However, no effect of SDS on dissociation constants of cresol red and methyl orange was observed. The dissociation constants of indicators were calculated with both the proposed and known chemometric (DATAN) method with a reasonable agreement on the data achieved.