Abstract
We developed a simple, accurate, and sensitive analytical method for determination of the lithium isotopic ratio of seawater, using a multi-collector ICP mass spectrometer（MC-ICP-MS）. The method involves a single-step column separation, and improvements in sensitivity and precision are achieved by the use of an X-type skimmer cone and relatively low plasma RF power on MC-ICP-MS. With this method, the δ7Li value in standard seawater（NASS-5）was measured to be ＋30.97 ± 0.31 ‰（2σ）, which is consistent with the reported value in previous studies. We obtained δ7Li ＝＋30.82 ‰ of surface seawater from the East China Sea, which is the same as those for open oceans, suggesting that the surface seawater is not influenced by meteoric water from the Eurasian Continent. As the sampling location is in the flow passage of the Kuroshio Current, the value represents the δ7Li value of the Kuroshio Current.
