Spectroscopic studies of interaction between xylenol orange and cationic surfactant in aqueous solution

The interaction of the triphenylmethane dye xylenol orange with cationic surfactants cetyltrimethylammonium bromide and cetylpyridinium chloride was studied by absorption spectrophotometry and principal component analysis of infrared spectra. Upon the addition of surfactants the yellow color of the acidic xylenol orange solution changed to purple-red. Changes in the absorption spectra of the mixture indicate strong interactions between dye and surfactants. These interactions were also monitored using ATR spectroscopy and the most prominent changes were observed in the vibration of the carbonyl group. The comparison of principal component loadings obtained from spectral data matrices for xylenol orange and mixtures of xylenol orange with surfactants revealed differences in infrared spectra caused only by the interaction of the surfactants with the dye.