Wavelength-dispersive x-ray fluorescence spectrometry of lanthanum and cerium in nodular cast iron

Abstract

Cerium and lanthanum can be determined in cast iron samples by wavelength-dispersive x-ray fluorescence spectrometry (x.r.f.). Excitation and detection conditions are evaluated, as is the required degree of surface finish of the castings. Standard samples for x.r.f. were obtained by careful determination of the cerium and lanthanum contents of specimen cast iron samples by neutron activation—γ-spectrometry. The calibration graphs obtained with these reference samples and tungsten tube excitation were linear for the ranges 3—30 mg kg −1 lanthanum and 3–60 mg kg −1 cerium. The relativ standard deviations of the determinations, for 400-s counting tims, ranged from 15% for samples containing 4 mg kt −1 La to 4% for samples containing 30 mg kg −1. For cerium, the corresponding numbers were 15% for 3 mg kg −1 and 2% for 60 mg kg −1. For unknown samples, the results obtained with these calibration graphs agreed within 3% with the neutron activation results.