Abstract
4-(2-Thiazolylazo)-6-bromoresorcinol (TAR-Br) was synthesized and its usefulness for spectrophotometric determination of 14 lanthanoid(III) ions was examined. The acid dissociation constants of the reagent and the stability constants of the complexes (1:1) were determined, and the complexing behavior was studied. The optimum pH for complexation lies between 6.8-8.7. Beer′s law holds up to about 2.5ppm of each lanthanoid, with a molar absorptivity of 6×104l mol-1 cm-1 eve near 553nm. The addition of ethanol produced some sensitization effect, due to solvation with the complexes. Both the molar absorptivities and the stability constants were larger in light Lanthanoids with the atomic number, but the latter were slightly lower in heavy Lanthanoids. TAR-Br was classified as a second ligand group member according to the Moeller′s type classification.
