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Oxygen Isotopic Reference

 δ18O Values of Oxygen Isotopic Reference Materials

Description 

NIST RM # 

Material

Nominal Unit Size

δ18OVSMOW

Footnote

Ref

δ18OVPDB

Ref

VSMOW

8535

water

20 mL

 0 ‰

*

1

 

 

SLAP

8537

water

20 mL 

–55.5‰

*

1

 

 

GISP

8536

water

20 mL 

–24.78 ‰ 

 

2

 

 

NBS 19

8544

limestone

0.4 g 

+28.65 ‰

 

15

–2.2* ‰

16

NBS 18

8543

carbonatite

0.4 g

+7.20 ‰

 

15

–23.01 ‰

14

NBS 28

8546

silica sand (optical)

0.4 g 

+9.58 ‰

 

2

 

 

NBS 30

8538

biotite

2 g 

+5.1 ‰ 

 

6

 

 

NBS 127

8557

barium sulfate

0.5 g  

+8.59 ‰

 

29

 

 

                 
IAEA-SO-5   barium sulfate 0.5 g +12.13 ‰   29    
                 
IAEA-SO-6   barium sulfate 0.5 g –11.35 ‰   29    
                 

USGS42

  human hair (Tibetian) 0.5 g +8.56 ‰   32    
USGS43   human hair (Indian) 0.5 g +14.11 ‰   32    

CO2-Heavy Paleomarine Origin

8562

CO2

2 tubes

+11.86 ‰

 

15

–18.49 ‰

14

CO2-Light, Petrochemical Origin

8563

CO2

2 tubes

–3.64 ‰

 

15

–33.52 ‰

14

CO2-Biogenic, Modern Biomass Origin

8564

CO2

2 tubes

+20.52 ‰

 

15

–10.09 ‰

14

USGS32

8558

potassium nitrate

0.5 g  

 +25.4 ‰

 

30

 

 

USGS34

8568

potassium nitrate

0.9 g

–27.78 ‰

 

29

 

 

USGS35

8569

sodium nitrate

0.9 g

+56.81 ‰

 

29

 

 

IAEA-NO-3

8549

potassium nitrate 

0.4 g

 +25.32 ‰

 

29

 

 

IAEA-CO-9

 

barium carbonate

1 g

15.04 ‰

 

15

–15.40 ‰

14

IAEA-600   caffeine 0.5 g –3.48 ‰   29    
                 
IAEA-601   benzoic acid 0.5 g +23.14 ‰   29    
                 
IAEA-602   benzoic acid 0.5 g +71.28 ‰   29    

*  Exact values defining the delta scale
** Isotope amount ratio

Recommendation on the Reporting of δ18O Measurements

At the 37th IUPAC General Assembly in 1993 in Lisbon, the Commission recommended guidelines for δ18O measurements.

Water
Relative n(18O)/n(16O) values (δ18O) of water should be expressed relative to VSMOW water (0 ‰) on a scale normalized such that the δ18O of SLAP water is –55.5 ‰ exactly and so stated in author’s report.

Carbonate
Relative n(18O)/n(16O) values ( δ18O) of carbonate should be expressed on a scale normalized such that the δ18O of SLAP reference water is –55.5 ‰ exactly relative to VSMOW water, and so stated in author’s report.  The measured value should be expressed either

  • relative to VPDB on a scale such that the δ18O of NBS 19 calcite is –2.2 ‰ exactly, stating the value of the oxygen isotopic fractionation factor used to calculate the δ18O of the carbonate sample and NBS 19 if they are not identical, or
  • relative to VSMOW water (0 ‰), stating the values of all isotopic fractionation factors upon which the δ18O measurement depends.

If the δ18O values cannot be reported on a normalized scale (perhaps because of the lack of a capability to analyze water samples), the author’s measured δ18O of NBS 18 carbonatite or other internationally distributed isotopic reference material should be reported, as appropriate, had it been analyzed with the samples.

Other Substances (Oxygen Gas, Sulfate, Silicate, Phosphate, etc.)
Relative n(18O)/n(16O) values ( δ18O) of all other oxygen-bearing substances should be expressed relative to VSMOW water (0 ‰) on a scale normalized such that the δ18O of SLAP water is  –55.5 ‰ exactly relative to VSMOW water, and so stated in author’s report, stating either

  • the values of all isotopic fractionation factors upon which a δ18O values depends, or
  • the author’s measured δ18O of NBS 28 quartz, NBS 127 barium sulfate, USGS35 sodium nitrate, or other internationally distributed reference material had it been analyzed with the samples.

If the δ18O values cannot be reported on a normalized scale (perhaps because of the lack of a capability to analyze water samples), the author’s measured δ18O of NBS 18 carbonatite or other internationally distributed isotopic reference material should be reported, as appropriate, had it been analyzed with the samples.

Authors should discontinue reporting their δ18O values relative to SMOW and PDB. 

The full recommendation appears in:
Reporting of stable hydrogen, carbon, and oxygen isotopic abundances, Coplen, T. B., Pure Appl. Chem., 66, 273-276 (1994).  [full text - pdf 242 KB] {H, C, O Isotopic Rept Guidelines.pdf}

References

1. Gonfiantini, R., Standards for stable isotope measurements in natural compounds, Nature, 271, 534-536 (1978).
2. Gonfiantini, R., Stichler, W., and Rozanski, K., Standards and intercomparison materials distributed by the International Atomic Energy Agency for stable isotope measurements, in Reference and intercomparison materials for stable isotopes of light elements, Vienna, Austria, International Atomic Energy Agency, IAEA-TECDOC-825, 13-29 (1995).
6. Coplen, T. B., Kendall, C., and Hopple, J., Intercomparison of stable isotope reference samples, Nature, 302, 236-238 (1983).
8. Böhlke, J. K., Mroczkowski, S. J., and Coplen, T. B., Oxygen isotopes in nitrate: new reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration, Rapid Comm. Mass Spectrom., 17, 1835-1846 (2003).
12. Coplen, T.B., Hopple, J.A., Böhlke, J.K., Peiser, H.S., Rieder, S.E., Krouse, H.R., Rosman, K.J.R., Ding, T., Vocke, Jr., R.D., Révész, K.M., Lamberty, A., Taylor, P., and De Bièvre, P., Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents, U.S. Geological Survey Water-Resources Investigations Report 01-4222, 98 p (2001).
14. Verkouteren, R. M.; Klinedinst, D.B., Value Assignment and Uncertainty Estimation of Selected Light Stable Isotope Reference Materials:  RMs 8543-8545, RMs 8562-8564, and RM 8566, NIST Special Publication 260-149, National Institute of Standards and Technology, Gaithersburg, Maryland (2004).
15. Calculated from data in ref (14) and the relation between VPDB and VSMOW given on page 36 of reference (12).
29. Brand, W. A., Coplen, T. B., Aerts-Bijma, A. T., Böhlke, J. K., Gehre, M., Geilmann, H., Gröning, M., Jansen, H. G., Meijer, H. A. J., Mroczkowski, S. J., Qi, H., Soergel, K., Stuart-Williams, H., Weise, S. M., and Werner, R. A., Comprehensive inter-laboratory calibration of reference materials for δ18O versus VSMOW using various on-line high-temperature conversion techniques, Rapid Comm. Mass Spectrom., 23, 999-1019 (2009).
30. Calculated from data in ref (8) and reference (29).
32. Coplen, T. B., and Qi, H., USGS42 and USGS43: Human-hair stable hydrogen and oxygen isotopic reference materials and analytical methods for forensic science and implications for published measurement results, Forensic Sci. Int. (2011), doi:10.1016/j.forsciint.2011.07.035

 

 

 

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