Producing Laboratory: TERC
N-labelled ammonium sulfate

Reference material IAEA-311 is aimed at δ15N calibrations at high δ15N enrichments. 

IAEA-311 was prepared from highly enriched 15N-labelled ammonium sulfate by dilution with the unlabelled compound in redistilled water. After mixing, evaporation, freeze drying, crystallization and further mixing, the material was dispensed into glass vials.

The values were established on international intercomparison organized by the IAEA Section of Nutritional and Health Related Environmental Studies [1].

AnalyteValueUnit95% Confidence Interval.NR/I/C
15N2.05Atom%2.03 - 2.0628R

[1] The isotopic compositions are given in parts per thousand difference from isotope ratio standard atmospheric N2 (Air)
(N) Number of accepted laboratory means which were used to calculate the recommended or information values and their respective confidence intervals about the mean value
(R/I) Classification assigned to the property value for analyte (Recommended/Information)


  1. PARR, R.M., CLEMENTS, S.A., Intercomparison of enriched stable isotope reference materials for medical and biological studies. IAEA Report NAHRES-5, INTERNATIONAL ATOMIC ENERGY AGENCY, Vienna, Austria (1991).
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