Precise Isotopic Measurement of Sub-nanogram Nd by Thermal Ionization Mass Spectrometry

Thermal ionization mass spectrometry (TIMS) was applied to the precise measurement of isotopic ratio of sub-nanogram Nd. With the Nd+ method and a new type Re ribbon filament, sub-nanogram (0.1-0.5 ng) standard samples of Nd were measured. Without adding any emitter or activator wading agents, 0.4-1 V 142Nd+ ion beam was obtained and could last more than 30 minutes under special focusing procedure. With increasing current, the mass fractionation effect tended to lower and more stable in the current range of 1 700-2 000 mA. The proposed method was applied to the analysis of 42 La Jolla international standard samples of 0.1-0.5 ng Nd and 18 LRIG-Nd in-house standard samples of 0.1-0.5 ng Nd . 143Nd/144Nd ratios measured were 0.511 852±0.000 002 (2SE) and 0.512 201±0.000 003 (2SE), which were in agreement with the reference values reported in literature.