2002 Volume 18 Issue 5 Pages 591-594
The absorption spectra of the 4f electron transitions of neodymium, praseodymium, holmium and erbium complexes with fleroxacin in the presence of cetylpyridinium chloride were studied by normal and derivative spectrophotometry. Their molar absorptivity at the maximum absorption bands are about 5.3 (at 571 nm) times greater for neodymium, 2.8 (at 483 nm) times greater for praseodymium, 12.6 (at 448.5 nm) times greater for holmium and 9.7 (at 519 nm) times greater for erbium than those in the absence of complexing agents. The second-derivative spectrum is used both to eliminate the interference from other rare earths and to improve the sensitivity. Beer’s law is obeyed from 3.0 - 70 µg ml-1 for neodymium and holmium, from 6.0 - 70 µg ml-1 for erbium, and from 12.0 - 70 µg ml-1 for praseodymium. The relative standard deviations are 1.9% and 1.5% for 7.5 µg ml-1 of neodymium and holmium, and 2.1% and 1.6% for 15.0 µg ml-1 of praseodymium and erbium, respectively. Their detection limits (signal-to-noise ratio = 2) are 3.2 µg ml-1, 1.3 µg ml-1, 1.1 µg ml-1 and 2.5 µg ml-1 for praseodymium, neodymium, holmium and erbium, respectively. A new system for the simultaneous determinations of the praseodymium, neodymium, holmium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.