Nonionic/Anionic Mixed Surfactants System for Colorimetric Determination of Metal-Dithizone Complexes.

Abstract

Dithizone (diphenyl thiocarbazone, H₂Dz) has been solubilized in a
mixed micellar solution of nonionic (poly (oxyethylene) (23) dodecanol)
(Brij 35) and anionic (sodium dodecylsulfate) (SDS) surfactants.
Increasing the surfactants concentration above the critical micelle
concentration produces more micelles that provide local nonpolar
microenvironments that enhance the solubility of the nonpolar organic
compounds in water. Metal ions bind the mixed micellar-solubilized
dithizone to form water-soluble colored chelates. Tile metal-dithizone
colored complexes are extracted to the nonpolar "stationary" micellar
phase. Potential application of the method for the determination of
different metal ions in water has been evaluated. The detection limit of
the method ranged from 3 to 6 ppb. Recoveries from individual metal ion
solution ranged from 95 to 100% with RSDs between 4-10%, and from
mixed metal ions solution ranged from 93-104% with RSDs between
3.5-12%. The recoveries of metal ions obtained in our method are better
than the recoveries obtained with the use of extraction in toxic
chlorinated hydrocarbons method.