MICELLAR COLORIMETRIC DETERMINATION OF DITHIZONE METAL-CHELATES

Surfactants have been used in the development of new methods for colorimetric analysis. Amphiphilic molecules (surfactants, detergents) on dissolution in water form organized molecular assemblies called micelles when an appropriate concentration, the critical micelle concentration (cmc), is exceeded. These micelles enhance the solubility of organic compounds in water by providing local nonpolar environments. A simple method for the determination of several metal ions has been developed using diphenylthiocarbazone (dithizone) and a nonionic surfactant, polyoxyethylene tert-octylphenol (Triton X-100). The metal-dithizone colored complexes are extracted into the nonpolar microenvironment of the surfactant, thereby eliminating tedious and time-consuming solvent extraction procedures using chlorinated solvents. The proposed method is faster, allows for the sequential determination of metal ions in the aqueous phase, and gives parts per million detection limits for the metal ions tested.