Determination of cerium and terbium from absorption bands of 4f-5d transitions by recording spectrum derivatives

Possibility of increasing selectivity of determining Ce(3) and Tb(3) in their common presence and in presence of other rare earths using derivative spectrophotometry is studied. For this purpose second-order derivatives of the bands of 4f-5d transitions of these elements in solutions of their chlorides and complexes with edta and oxyethylidene-diphosphonic acid are used. It is shown that selectivity of determining these elements in the presence of other rare earths and Fe(3) considerably increases, the reproducibility of analysis results (at n=6, Sr=0.05) being satisfactory