Spectrophotometric Studies on the Interaction of Eriochrome Black T with Cetylpyridinium Bromide and Metal Ions

The absorption spectra (450-800 nm) of the dye Eriochrome Black T, its complexes with cetylpyridinium bromide (CPB) and CPB-metal ions, dye-CPS and dye-CPB-metal ion complexes have been studied. The dye showed marked bathochromic and hyperchromic effects in the presence of the surfactant. The optimum dye-to-surfactant ratio for maximum spectral shift was found to be 1:6 Absorption spectrum of dye-surfactant complex was significantly altered in the presence of metal ions. Dye surfactant complex could be used as a modified reagent for micro-determination of eight metal ions. The dye-surfactant-metal ion complexes could be represented as [Erio T (CPB)₆]_yM with y varying from 1 to 4 for different metal ions.