3RD-DERIVATIVE SPECTROPHOTOMETRIC DETERMINATION OF NEODYMIUM AND ERBIUM IN MIXED RARE-EARTHS WITH 2-(DIPHENYLACETYL)INDAN-1,3-DIONE AND DODECYL BENZENESULFONIC ACID SODIUM-SALT

The absorption spectra of 4f electron transitions of neodymium and erb ium complexes with 2-(diphenylacetyl)indan-1,3-dione and dodecylbenzen esulfonic acid sodium salt have been studied by normal and derivative spectrophotometry. The use of third-derivative spectra both eliminates the interference from other REEs and enhances the sensitivity for neo dymium and erbimn. Beer's law is obeyed for less than or equal to 21.6 mu g cm(-3) of neodymium and less than or equal to 25.1 mu g cm(-3) o f erbium. The detection limits (with a signal-to-noise ratio of 2) are 0.28 and 0.77 mu g cm(-3) for neodymium and erbium, respectively. A m ethod for the direct determination of neodymium and erbium in mixed RE Es and lanthanide-based samples with good accuracy and selectivity is described.