International Chemical Safety Card (ICSC): ICSC_0184
Reference material USGS32 is aimed at δ15N and δ18O calibrations.
USGS32 is potassium nitrate KNO3 prepared in 1992 by J. K. Böhlke, U.S. Geological Survey [1] dissolving and re-crystallizing a mixture of normal reagent salt and 15N enriched salt.
Its δ15N value is based on interlaboratory comparison [2].
| Stable Isotope Ratio | Reference Value | Standard Uncertainty with k=1 |
| δ15Nair(‰) | +180 | 0 |
| δ18OVSMOW-SLAP(‰) | +25.4 | 0.2 |
Note: A consensus δ15N value of +180‰ (without uncertainty) relative to N2 in air was assigned to USGS32. Uncertainty, calculated as standard deviation, after elimination of outliers, from the 11 accepted data sets, each being obtained by different laboratories and different methods of determination, is 1.3 ‰.
References:
BÖHLKE, J.K., GWINN, C.J., COPLEN, T.B., New reference materials for nitrogen isotope ratio measurements, Geostandards Newsletter 17 1 (1993) 159-164.
BÖHLKE, J.K., COPLEN, T.B., Interlaboratory comparison of reference materials for nitrogen isotope ratio measurements. Proceedings of a consultants meeting held in Vienna, 1 - 3. Dec. 1993. IAEA-TECDOC-825, INTERNATIONAL ATOMIC ENERGY AGENCY, Vienna, Austria (1995) 51-66.
