Separation of spectral and non-spectral interferences by on-line high performance ion chromatography inductively coupled plasma sector field mass spectrometry (HPIC-ICP-SFMS) for accurate determination of U-234, U-235, U-238and Th-232 in industrial ores

A novel and versatile method for the determination of Th-232, U-234, U-235 and U-238 in milling grade ores and intermediates containing high amounts o f rare earth elements (REE) was developed. Spectral and non-spectral interf erences were eliminated by on-line matrix separation with high performance ion chromatography (HPIC) using 2,6-pyridinedicarboxylic acid (PDCA) as com plexing agent. Hyphenation to inductively coupled plasma sector field mass spectrometry (ICP-SFMS) introduced a highly sensitive method of detection. Quantification of uranium and thorium could be established using external c alibration and post-column internal standardization. Elemental levels down to concentrations of pg g(-1) to ng g(-1) in samples containing rare earth elements as the main matrix components could be assessed. The method was va lidated for U-235 and U-238 by comparison of isotope dilution mass spectrom etry (IDMS) results without and with on-line matrix separation using a matr ix matching pure cerite carbonate sample containing about 0.5 ng g(-1) U-23 5 and 65 ng g(-1) U-238. The results of the external calibration were in go od agreement with the IDMS results and overlapped within their uncertaintie s. Th-232 was quantified to about 30 ng g(-1) (solid material) by on-line H PIC-ICP-SFMS using U-233 as internal standard. The results were in excellen t agreement with those obtained by HPIC-ICP-SFMS using indium as internal s tandard. Measurement of a series of industrial samples proved the versatili ty of the method and can give a quick assessment of whether a material is s uitable for a further production process or not, since isotope dependent li mit values have to be determined.