A Comparative Study of Metachromasy Induced by Anionic Polelectroytes in Toluidine Blue

The interaction of two anionic polyelectrolytes, namely, sodium alginate (NaAlg) & sodium heparin ate (NaHep) with a cationic dye Toluidine Blue (TB) has been investigated by spectrophotometric method. The polymers induced metachromasy in the dyes resulting in the shift of the absorption maxima of the dyes towards shorter wavelengths. The stability of the complexes formed between TB and sodiumalginate was found to be lesser than that formed between TB and sodiumheparinate. This fact was further confirmed by reversal studies using alcohols, urea and electrolytes. The interaction parameters revealed that binding between TB and anionic polyelectrolytes was mainly due to electrostatic interaction andhydrophobicforces. The effect of the temperature on to metachromasy has beendiscussed.