Results of an interlaboratory comparison of a liquid chromatography-isotope ratio mass spectrometry method for the determination of 13C/12C ratios of saccharides in honey.

BACKGROUND Stable carbon isotope analysis of sugars in honey by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) is a useful tool for detecting honey adulteration with extraneous sugar. Purity criteria based on 13C/12C ratios of saccharides in honey, determined by LC-IRMS of a large number of authentic honey, have been elaborated. However, no interlaboratory comparison (ILC) was performed until now to estimate 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. Repeatability standard deviation for the determination of δ13C values of fructose and glucose varied between 0.09 and 0.13 ‰, 0.08 and 0.24 ‰ for disaccharides, and 0.36 and 0.68 ‰ for trisaccharides. The reproducibility standard deviation varied between 0.19-0.43 ‰ for the monosaccharides, 0.24-0.36 ‰ for disaccharides and 0.36-0.68 ‰ for trisaccharides. CONCLUSIONS Based on the obtained precision data the LC-IRMS method for the determination of 13C/12C ratios saccharides in honey was considered fit for conformity assessment of honey with established purity criteria. HIGHLIGHTS Precision estimates for a liquid chromatography-isotope ratio mass spectrometry method to determine 13C/12C ratios of saccharides in honey were obtained through an interlaboratory comparison. The data created can form the basis for the standardization of the method by interested Standard Developing Organizations for use in official control.