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Sci Justice. 2019 Jan;59(1):9-19. doi: 10.1016/j.scijus.2018.08.003. Epub 2018 Aug 16.

Lessons learned from inter-laboratory studies of carbon isotope analysis of honey.

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LGC Limited, Queens Road, Teddington, Middlesex TW11 0LY, UK. Electronic address:
LGC Limited, Queens Road, Teddington, Middlesex TW11 0LY, UK.
TUBITAK Ulusal Metroloji Enstitüsü (TÜBİTAK UME), Turkey.
Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
National Measurement Institute Australia, 105 Delhi Road, North Ryde, NSW 2113, Australia.
National Institute of Metrology, 18 Bei San Huan Dong Lu, Chaoyang District, Beijing 100013, PR China.
D.I. Mendeleev Institute for Metrology, St. Petersburg, Russia.
IsoForensics, Inc., 421 Wakara Way, Suite 100, Salt Lake City, UT 84108, USA.
The Netherlands Forensic Institute, PO Box 24044, 2490 AA, Den Haag, the Netherlands.
Food Forensics, Innovation Centre, Norwich Research Park, Norwich NR4 7GJ, UK.
Department of Food Quality and Nutrition, Research and Innovation Centre, Fondazione Edmund Mach (FEM), Via E. Mach, 1, 38010 S. Michele all'Adige, TN, Italy.
Analytica Laboratories, Ruakura Research Centre, 10 Bisley Road, Hamilton 3240, New Zealand.
Queensland Health Forensic and Scientific Services, P.O. Box 594, Archerfield, Queensland 4108, Australia.


Forensic application of carbon isotope ratio measurements of honey and honey protein to investigate the degree of adulteration with high fructose corn syrup or other C4 plant sugars is well established. These measurements must use methods that exhibit suitable performance criteria, particularly with regard to measurement uncertainty and traceability - low levels of adulteration can only be detected by methods that result in suitably small measurement uncertainties such that differences of 1‰ or less can be reliably detected. Inter-laboratory exercises are invaluable to assess the state-of-the art of measurement capabilities of laboratories necessary to achieve such performance criteria. National and designated metrology institutes from a number of countries recently participated in an inter-laboratory assessment (CCQM-K140) of stable carbon isotope ratio determination of bulk honey. The same sample material was distributed to a number of forensic isotope analysis laboratories that could not participate directly in the metrological comparison. The results from these studies have demonstrated that the majority of participants provided isotope delta values with acceptable performance metrics; that all participants ensured traceability of their results; and that where measurement uncertainties were reported; these were fit-for-purpose. A number of the forensic laboratories only reported precision rather than full estimates of measurement uncertainty and this was the major cause of the few instances of questionable performance metrics. Reporting of standard deviations in place of measurement uncertainties is common practice outside metrology institutes and the implications for interpretations of small differences in isotopic compositions are discussed. The results have also highlighted a number of considerations that are useful for organisers of similar inter-laboratory studies in the future.


Inter-laboratory comparison; Isotope ratio; Metrology; Performance metrics

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