Measurement of lithium isotopic ratios as lithium tetraborate ions

✍ Scribed by M.J Bickle; H.J Chapman; C.-F You

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 218 KB
• Volume: 202
• Category: Article
• ISSN: 1387-3806
• DOI: 10.1016/s1387-3806(00)00253-0

✦ Synopsis

Determination of 6 Li/ 7 Li ratios using Li 2 BO 2 ϩ ions analysed by thermal ionisation mass spectrometry with ion counting has been investigated by numerical simulation and experiment. It is possible to solve for one or more of the 6 Li/ 7 Li ratio, 10 B/ 11 B ratio and fractionation if one or more of the ratios of the 54, 55, 56, 57, 58 and 59 masses of Li 2 BO 2 ϩ are measured. Monte Carlo simulation of data sets suggests that within-sample precision on measurement of Li 2 BO 2 ϩ mass ratios is largely limited by counting statistics and should result in precision as good as 0.25‰ (1) on the 6 Li/ 7 Li ratio. However repeatability of 6 Li/ 7 Li and 10 B/ 11 B ratios gives precisions no better than approximately Ϯ3‰ (1) and the probable cause is fractionation of the 6 Li/ 7 Li ratio on the filament due to the large Li ϩ ion beam produced during analysis of Li 2 BO 2 ϩ . Plots of variation of sample fractionation with time confirms that fractionation is primarily controlled by varying 6 Li/ 7 Li ratio rather than varying fractionation of Li 2 BO 2 ϩ or 10 B/ 11 B ratio. (Int J Mass Spectrom 202 (2000) 273-282) © 2000 Elsevier Science B.V.