THE SPECTROPHOTOMETRIC DETERMINATION OF ELEMENTS WITH CHROMAZUROL-S IN THE PRESENCE OF CETYLTRIMETHYL-AMMONIUM BROMIDE AND TRITON X-100 .2. MULTICOMPONENT SPECTROPHOTOMETRIC DETERMINATION OF THE SUM OF THE RARE-EARTH ELEMENTS, AL, FE AND TH USING MULTIVARIATE CALIBRATION WITH PLS DATA EVALUATION

A procedure was developed for the simultaneous spectrophotometric determination of the sum of the rare earth elements, Al, Fe and Th using chromazurol S in the presence of cetyltrimethylammonium bromide and Triton X-100 for optimized conditions at pH 5.5 and 10.2. Multivariate calibration and the PLS procedure were employed to evaluate data for a variable number of calibration solutions and wavelength. A new procedure was described for combination of the data of independently measured systems at both pH values. The errors in the determination of the concentration values for Al, Fe, Th and the sum of the rare earth elements in model solutions and in the concentrates of the rare earth elements were not greater than 10 rel.%.