Interaction between thallium(III) bromide and dicyclohexano-18-crown-6 immobilized on silica

The adsorption of cis-syn-cis-dicyclohexano-18-crown-6 on silica gel from o rganic solvents was studied. In the adsorption from chloroform solutions, t he immobilization of the reagent molecules at the surface was coplanar. Hyd rogen bonds between surface silanol groups and oxygen atoms of the polyethe r ring of the crown ether play an important role in the immobilization of t he reagent. The reaction between thallium(Ill) bromide and the immobilized reagent was studied. The composition of complex compounds formed at the sur face of the modified adsorbent was found. A procedure was proposed for the sorption-spectrophotometric determination of thallium(III) (greater than or equal to 0.05 mg/L) in the presence of heavy metal ions.