Sensitive spectrophotometric determination of holmium (III) in geological and lasers samples with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

Reaction between Ho(III) and 2-(5-bromo-2-pyridylazo)-5-diethylamino-phenol (5-Br-PADAP) was studied for delineating optimal conditions for complexati on. This reagent can be used for the spectrophotometric determination of Ho (III) in concentrations ranging from 0.02 to 1.35 mg l(-1) '[epsilon = (1.2 9 +/- 0.04) x 10(5) l mol(-1) cm(-1)] Maximum absorption of the complex is at 580 nm. The reaction takes place at pH between 9.1 and 10.6 (lambda(max) = 580 nm). In the presence of Triton X-100 this complex is soluble in wate r The procedure has been successfully applied on the determination of Ho(II I) in geological and lasers samples.