Simultaneous spectrophotometric determination of lanthanum, cerium, praseodymium and neodymium in monazite sand

A possibility of simultaneous spectrophotometric determination of lanthanoids, including the reighboring ones, using the dependence of the content and total optical density of their complexes with 4-(2-pyridylazo)resopcinol (PAR) on the pH value is shown. On this basis a method for determining La, Ce and the sum of Pr and Nd in monazite sand is developed. Thorium is extracted from the analytical samples using N-benzoylphepylhydroxylamine. To separate La, Ce, Pr and Nd from other lanthanoids, the extraction of rare earth complexes with 1-(2 pyridylazo)-2-naphthalane (PAN) into tetrachloride carbon is used. At pH=7.7 La-, Ce-, Pr-, Nd- and Sm complexes with PAN are extracted partially, and complexes of the rest of lanthanoids are extracted nearly completely. After analysis the errors for extractability in separation have been introduced. The obtained results have shown a satisfactory accuracy of the proposed method