Abstract: This paper describes a new procedure for the determination of Dy,Eu,Sm and Tb by using laser induced derivative fluorimetry. The analytical method is based on the use of TFA(Trifluoroacety-lacetone) and TOPO(Trioctylphosphine oxide) as ligands. The first derivative technique was used for the correction of background and reduction of interference among spectra. The effects of foreign ions were investigated. The mentioned method was used to simultaneously determine the amount of Dy,Eu, Sm and Tb in yttrium oxide without pre-separation. It is concluded'that this procedure is satisfactory for the simultaneous detection of these four rare earth ions.

Key words: Laser, Fluorimetry, Derivative spectrum, Analysis of rare earths elements