Polarographic determination of Ce(III) and Tm(III) using rare earth-DBF-chlorophosphonazo complex

The electrochemical behaviour of the DBF-chlorophosphonazo (DBF-CPA)-rare earth (RE) complex has been investigated in this paper. A highly sensitive polarographic adsorption wave was found in the RE(III)-DBF-CPA system and a new method for determination of trace total RE(III) has been established. The limit of detection was 1.8 x 10(-8)M. The results of determination of the total RE(III) content in Chinese standard reference materials of cast-iron and alloy steel were in good agreement with the certified values. The polarographic adsorptive waves of Ce(III) and Tm(III)-DBF-CPA overlap seriously. In order to improve the selectivity of determination, a non-linear regression model was employed to fit the peak height of the polarographic wave and the concentrations of Ce(III) and Tm(III). The predictive accuracy of this model for simulant mixtures was satisfied.