Accurate and precise lithium isotopic determinations of igneous rock samples using multi-collector inductively coupled plasma mass spectrometry

A second-generation multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was applied to lithium isotopic measurements. The high sensitivity of the ICP-MS enabled high precision (+/-0.82parts per thousand, 2sigma) analyses with small amount of Li (similar to45 ng Li). A single-step column separation protocol was established with which rapid purification of lithium from rock solutions can be carried out with reduced blank (< 10 pg). The influence of potential sources of error for acquisition of lithium isotopic data introduced during the separation, such as matrix effects and isotopic fractionation due to incomplete recovery, were examined with an artificially mixed solution of a composition similar to that of basalt, which was doped with Li isotopic standard reagent. The examinations demonstrated that our protocol suffered from negligible isotopic fractionation. The Li isotopic ratios obtained by our method for seawater and standard rocks (JA-1, JB-2, and JB-3) agree well with those of previously reported data by Moriguti and Nakamura [1,2], which were determined using a four-step column separation method and thermal ionisation mass spectrometry (TIMS). Our separation protocol combined with a sensitive MC-ICP-MS will enable Li isotopic analyses on silicate rock with low Li contents, such as meteorite and peridotites with increased sample throughput. (C) 2002 Elsevier Science B.V. All rights reserved.