CIAAW

Free CSS Menu Builder Css3Menu.com

 

 

Lithium Isotopic Reference

Isotope-amount Ratios of Lithium Isotopic Reference Materials

Description 

NIST RM # 

Material

Nominal Unit Size

n(6Li)/n(7Li)

Footnote

Ref

L-SVEC

8545

lithium carbonate 

0.4 g 

0.082 15

**

4

IRMM-015

 

lithium carbonate 

50 mg

21.897

**

25

IRMM-016

 

lithium carbonate 

1 g

0.082 121

**

26

** Isotope-amount ratio

Guidelines for Reporting Lithium Delta Values

Guidelines for reporting lithium delta values were published in Atomic weights of the elements 1995, T. B. Coplen. Pure Appl. Chem.,68, 2339-2359 (1996).  [full text - pdf 1347 KB] {TSAW1995.pdf}

Relative lithium isotope-amount ratios in geochemical and environmental studies commonly are reported as δ7Li values in terms of n(7Li)/n(6Li) ratios. It was brought to the attention of the Commission that some laboratories are reporting δ6Li values by using n(6Li)/n(7Li) ratios. This is confusing because (i) δ7Li values are opposite in sign to δ6Li values, (ii) the absolute values of δ7Li and δ6Li are not equal, and (iii) samples with more positive δ values are commonly thought of as being more dense or “heavier,” but samples with more positive δ6Li values are less dense. Therefore, to eliminate possible confusion in the reporting of relative lithium isotope-amount ratio data, the Commission recommended that relative lithium isotopic measurements of all substances be expressed as δ7Li values in terms of n(7Li)/n(6Li) ratios relative to the internationally distributed lithium carbonate isotopic reference material L-SVEC (0 ‰).

Reporting of δ6Li values, expressed in terms of n(6Li)/n(7Li) ratios, should be discontinued.

References

4. Qi, H.P., Taylor, P.D.P., Berglund, M., and De Bièvre, P., 1997, Calibrated measurements of the isotopic composition and atomic weight of the natural Li isotopic reference material IRMM-016,  Int. J. Mass Spectrom. Ion Proc., 171, 263-268 (1997).
25. IRMM, Certificate, Isotopic Reference Material IRMM-015, Institute of Reference Materials and Measurements, Geel, Belgium (2005).
26. IRMM, Certificate, Isotopic Reference Material IRMM-016, Institute of Reference Materials and Measurements, Geel, Belgium (2005).

 

 
2010 Commission on Isotopic Abundances and Atomic Weights | a commission of the International Union of Pure and Applied Chemistry