USGS25

• Unit Size: 0.5 g
• Price per Unit: 200 EUR
• Report: TECDOC-825 (pdf)
• Date of Release: 9/1/1995
• Reference Sheet: download (pdf)
• Contact point: Analytical-Reference-Materials.Contact-Point@iaea.org

​Reference material USGS25 is aimed at δ¹⁵N calibrations.

USGS25 is a dried salt of ammonium sulfate [(NH₄)₂ SO₄]) which was prepared in 1992 by J. K. Böhlke, U.S. Geological Survey [1]. The material was prepared from Fisher ammonium sulfate (A938-500, lot #915021) and Cambridge Isotopes ammonium sulfate (99.99% 14N; lot BI 1328) BI 1050) by dissolving and re-crystallizing a mixture of normal reagent salt and ¹⁵N depleted salt. The δ¹⁵N value of this reference material is the result of the statistical evaluation of interlaboratory comparisons [1,2].

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1. References:
   1. BÖHLKE, J.K., GWINN, C.J., COPLEN, T.B., New reference materials for nitrogen isotope ratio measurements, Geostandards Newsletter 17 1 (1993) 159-164.
   2. 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, IAEA, Vienna, Austria (1995) 51-66.