[Simultaneous determination of La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+ in their mixtures by multi-system multi-wavelength computational spectrophotometry].

Since the spectra of the rare earth color complexes are rather similar, it is very difficult to determine simultaneously rare earth elements in their mixtures. To reduce the collinearity of multicomponent spectra, different amounts of EDTA-Na2P2O7 were added to the rare earth-DBC-CPA(2-(4-chloro-2-phosphonophenylazo)-(2,6-dibromo-4- chlorophenylazo) 1,8-dihydroxy-3,6-naphthalene-difulfonic acid) color system. The flexible tolerance method which has high numerical stability and resolving power was used to improve the reliability of simultaneous spectrophotometry. The method has been applied to simultaneous spectrophotometric determination of seven components of rare earth elements(La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+) in synthetic samples with satisfactory results.