SELECTIVE DETERMINATION OF NEODYMIUM AND ERBIUM IN MIXTURES WITH OTHER LANTHANIDES BY 2ND-DERIVATIVE SPECTROPHOTOMETRY OF COMPLEXES WITH BENZOYL-INDAN-1,3-DIONE AND CETYLPYRIDINIUM CHLORIDE

The absorption spectra of 4 f electron transitions of the neodymium an d erbium complexes with benzoyl-indan-1,3-dione and cetylpyridinium ch loride have been studied by conventional and derivative spectrophotome try. The second-derivative spectrum has been used to eliminate the int erference of the other lanthanides, and to increase the sensitivity by a further factor of 4-6. Beer's Law is obeyed for 6-29 mu g/ml Nd and 7-33 mu g/ml Er. The relative standard deviations evaluated from 10 i ndependent determinations of 5.0 mu g/ml Nd and Er were 1.1% (Nd) and 1.6% (Er). The detection limits obtained from the sensitivity of the c alibration graphs and 3s(b) (standard deviation of the blank, n = 11) were 0.63 mu g/ml Nd and 0.61 mu g/ml Er. The quantification limits (1 0s(b)) were 2.1 mu g/ml Nd and 2.0 mu g/ml Er. A method for the direct determination of neodymium and erbium in rare earth mixtures with goo d accuracy and selectivity is proposed.