Two new defatted beef reference materials, CAAS-1801 and CAAS-1802, for carbon and nitrogen stable isotope ratio measurements.

RATIONALE: Isotope reference materials are essential to enable reliable and comparable isotope data across multiple laboratories. Although many reference materials already exist, the best reference materials should mimic the unknown samples, so new reference materials continue to evolve with the development of isotope research in new product areas. METHODS: Two defatted beef reference materials, CAAS-1801 and CAAS-1802, with substantially different δ13 C values (due to difference in dietary intake), have been prepared as reference materials for stable C and N isotope analysis of meat tissue. Homogeneity, and short- and long-term stability tests of these reference materials have been performed. The δ13 C and δ15 N values of both materials were measured for two-point isotopic normalization against international reference materials by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). A total of nine international laboratories were selected for the joint evaluation. Cochran statistical analysis yielded the values reported here. RESULTS: The defatted beef reference material CAAS-1801 from Heilongjiang province has a δ13 C value of -13.58 ± 0.56‰ relative to VPDB and a δ15 N value of 4.23 ± 0.56‰ relative to N2 in air. The defatted beef reference material CAAS-1802 from Sichuan province has a δ13 C value of -25.03 ± 0.45‰ and a δ15 N value of 4.36 ± 0.69‰. CONCLUSIONS: The two defatted beef reference materials were found to be isotopically stable across a range of ambient temperatures, and to have low volatility and toxicity, which enables them to be useful as stable isotope reference materials in the field of authentication and traceability of meat.