Isotope ratio measurement of lead, neodymium and neodymium-samarium mixtures, hafnium and hafnium-lutetium mixtures with a double focusing multiple collector inductively coupled plasma mass spectrometer

An inductively coupled plasma (ICP) source coupled to a double focusing magnetic sector mass analyser equipped with seven Faraday detectors has been used to measure the isotopic ratios of lead reference materials using a thallium correction technique. The addition of Tl to the Pb standards and the subsequent simultaneous measurement of the Tl and Pb isotopes allowed a correction for mass discrimination. Measurement of six samples of National institute of Standards and Technology (NIST) (formerly National Bureau of Standards) Standard Reference material Pb-982 revealed exp 208 Pb: exp 204 Pb = 36.702 plus/minus 0.022, exp 207 Pb: exp 204 Pb = 17.141 plus/minus 0.009, and exp 206 Pb: exp 204 Pb = 36.711 plus/minus 0.021 compared with the NIST certified values of 36.744 plus/minus 0.050, 17.159 plus/minus 0.025 and 36.738 plus /minus 0.037, respectively. All errors are given as 2 sigma . The measurement of each sample used approx 200 ng of Pb and took 100 s. Measurement of six neodymium samples (obtained from Scripps Institute of Oceanography, La Jolla, California, USA), where internal normalization to exp 146 Nd: exp 145 Nd is possible, revealed a exp 143 Nd: exp 144 Nd ratio of 0.511854 plus/minus 0.000039 compared with the accepted value of 0.511859. Measurement of six La Jolla Nd samples contaminated with a similar concentration of samarium revealed a exp 143 Nd: exp 144 Nd ratio of 0.511854 plus/minus 0.000059. The measurement of each mixed sample used approx 100 ng of Nd. Similarly measurement of six samples of Johnson Matthey Company (JMC) 475 Hafnium, normalized to exp 179 Hf: exp 177 Hf, revealed a exp 176 Hf: exp 177 Hf ratio of 0.282194 plus/minus 0.000020 compared with the accepted value of 0.282195 plus/minus 0.000015. Measurement of six samples of JMC 475 Hf contaminated with a similar concentration of lutetium revealed a exp 176 Hf; exp 177 Hf ratio of 0.282213 plus/minus 0.000023. The measurement of each mixed sample used approx 400 ng of Hf.