Results of an Interlaboratory Comparison of a Liquid Chromatography–Isotope Ratio Mass Spectrometry Method for the Determination of (13)C/(12)C Ratios of Saccharides in Honey

BACKGROUND: Stable carbon isotope analysis of sugars in honey by LC–isotope ratio mass spectrometry (IRMS) is a useful tool for detecting adulteration of honey with extraneous sugar. Purity criteria based on (13)C/(12)C ratios of saccharides in honey, determined by LC–IRMS of a large number of authentic honey samples, have been elaborated. However, no interlaboratory comparison (ILC) has yet been performed to estimate the precision of the method under reproducibility conditions. OBJECTIVE: To address this knowledge gap an ILC involving 14 laboratories and using six honey samples was conducted. METHODS: The participants were allowed to use their LC–IRMS-based method of choice for sample preparation and compound separation. RESULTS: The precision figures were estimated according to ISO 5725:1994. The repeatability relative standard deviation (RSD(r)) for the determination of δ(1)(3)C values of fructose and glucose varied between 0.3 and 0.5%, with 0.3 and 1.0% for disaccharides, and 0.7 and 2.8% for trisaccharides. The RSD(R) varied between 0.8 and 1.8% for the monosaccharides, 1.0 and 1.5% for disaccharides, and 1.4 and 2.8% for trisaccharides. CONCLUSION: Based on the obtained precision data the LC–IRMS method for the determination of (13)C/(12)C ratios of saccharides in honey was considered fit for the conformity assessment of honey with established purity criteria. HIGHLIGHTS: Precision estimates for a LC–IRMS method to determine (13)C/(12)C ratios of saccharides in honey were obtained through an ILC. The data created can form the basis for the standardization of the method by interested standards-developing organizations for use in official control.