Accurate measurement of isotope amount ratios of lead in bronze with multicollector inductively coupled plasma mass spectrometry

Isotope amount ratios of lead in a bronze sample have been successfully determined using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). Matrix separation conditions were tested and optimized using ion exchange chromatography with anion-exchange resin, AG1-X8, and sequential elution of the 0.5 M HBr and 7 M HNO₃ to separate lead from very high contents of copper and tin in bronze matrix. Mercury was also removed efficiently in the optimized separation condition. The instrumental isotope fractionation of lead in the MC-ICP-MS measurement was corrected by the external standard sample bracketing method using an external standard, NIST SRM 981 lead common isotope ratio standard followed by correction of procedure blank to obtain reliable isotope ratios of lead. The isotope ratios, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁶Pb, of lead were determined as 18.0802 ± 0.0114, 15.5799 ± 0.0099, 38.0853 ± 0.0241, and 2.1065 ± 0.0004, respectively, and the determined isotope ratios showed good agreement with the reference values of an international comparison for the same sample within the stated uncertainties.