Interactions of 2,3,5-triphenyl-2H-tetrazolium chloride with poly(sodium 4-styrenesulfonate) studied by diafiltration and UV–vis spectroscopy

The interaction of the water-soluble polymer poly(sodium 4-styrenesulfonate) with 2,3,5-triphenyl-2H-tetrazolium chloride is studied. Diafiltration experiments at pH 4, 7.5, and 10, and in the presence of NaNO3 at different concentrations show weak interactions of the low molecular weight molecule and the polymer with apparent dissociation constants ranging between 0.6 and 6, and strong interactions, detectable in the absence of NaNO3, with apparent dissociation constants ranging between 0.04 and 0.2, if the effect of the interactions of the water-soluble polymer with the diafiltration cell components is neglected. Apart from hydrophobic forces this is attributed to both long-range and short-range electrostatic forces. The short-range interaction is reflected in UV–vis spectroscopic studies by a decrease on the intensity of the maximum at 248 nm.