Determination of Trace Amounts of Antimony and Boron in High-Purity Iron and Steel by Isotope Dilution/Inductively Coupled Plasma Mass Spectrometry

The highly sensitive and precise determination method for trace amounts of Sb and B in high-purity iron and steel has been established by the isotope dilution/Inductively coupled plasma mass spectrometry. For the determination of Sb, the iron matrix was separated by anion-exchange chromatography using Dowex I-X8 in hydrofluoric acid solution, and the isotope ratio (121Sb/123Sb) of the HNO3/H2O2 eluate was measured by ICP-MS. The isobaric interference of 123Te was corrected by subtracting the intensity of 123Te obtained by the relative intensity of 123Te and 125Te. For the determination of B, after the treatment of sulfuric acid-phosphoric acid fuming for the complete decomposition of boron nitride, B was separated by the anion-exchange chromatography using Amberlite IRA-743 at pH 8. The CyDTA was added to prevent the hydrolysis of iron. The isotope ratio (11B/10B) of the HCl eluate was measured by ICP-MS. By these methods, Sb and B in the range of μg/g to sub-μg/g could be determined with good precision. The limit of detection is 5.8 ng/g for Sb and 16 ng/g for B in steel.