Determination of vanadium and molybdenum by atomic-absorption spectrophotometry

A method is described for the determination by atomic-absorption spectrophotometry of vanadium and molybdenum, up to the milligram level, in samples of yellow cake, uranium-bearing minerals and geochemical standards. After attack with acids these two elements are separated from each other and from matrix elements by means of anion-exchange in 6M hydrochloric acid on the strongly basic anion-exchange resin Dowex 1, X8 (chloride form). Vanadium is unadsorbed and passes into the effluent while molybdenum is adsorbed on the resin. For the elution of molybdenum a mixed aqueous-organic solvent system consisting of methanol and 6M hydrochloric acid (9: 1 v/v) is used. After evaporation of the 6M hydrochloric acid effluent and of the mixed aqueous-organic eluate vanadium and molybdenum are determined by atomic-absorption spectrophotometry. The method was tested by analysing numerous samples with contents ranging from a few ppm to milligram amounts of vanadium and molybdenum. For comparison, the concentrations of these two elements were determined in a large number of samples by spectrophotometric and titrimetric procedures. In all cases very good agreement of results was obtained.