SPECTROPHOTOMETRIC DETERMINATION OF GADOLINIUM(III) WITH 2-(5-BROMO-2-PYRIDYLAZO)-5-DIETHYLAMINOPHENOL (5-BR-PADAP)

Reaction between gadolinium(III) and 2-(5-bromo-2-pyridylazo)-5-diethy laminophenol (5-Br-PADAP) was studied for delineating optimal conditio ns for complexation. This reagent can be used for the spectrophotometr ic determination of Gd(III) in concentrations ranging from 0.04 to 1.2 ppm (a = 1.76(+/-0.03) x 10(5) (l.-1 mole-1 . cm). The reaction takes place at a pH between 9.2 and 11.6. In the presence of Triton X-100 t his complex is soluble in water. In order to overcome difficulties cau sed by the presence of other lanthanides, an ion exchange chromatograp hic technique was used.