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Lithium was determined in BCR Candidate Reference Materials 303 and 304 by isotope dilution mass spectrometry, using the state of the art performance of isotope-specific methods established during previous certifications of 6LiF reference targets. After reconstitution of the serum, four aliquots of each of the candidate materials from different bottles were spiked with an enriched 6Li spike which is now available as CBNM IRM-615 and has a certified 6Li/7Li ratio of 21.78 +/- 0.12 and a certified lithium concentration of 4.001 +/- 0.028 micromol/g solution. The serum aliquots were digested in a HNO(3)/H(2)O(2) mixture and, after evaporation of the acid, the lithium was separated on a cation exchange column eluted with 0.3 M HCl and used as LiCl for mass spectrometric measurement. A control sample BCR X was also analysed. The chemical preparation method was controlled by assaying NBS (NIST) SRM 909. The chemical blank was determined by IDMS using 6Li enriched CBNM IRM-615 and the measurements corrected for isotopic fractionation using the Isotopic Reference Material CBNM IRM-016. The final results had an overall uncertainty of 1.2 and 1.5% respectively, and compared favourably with the values proposed by BCR for certification, but with a smaller, better uncertainty.

Additional information

Bibliographic Reference: Paper presented: BERM-5, Aachen (DE), May 11-14, 1992
Availability: Available from (1) as Paper EN 36838 ORA
Record Number: 199211132 / Last updated on: 1994-11-29
Original language: en
Available languages: en