Liquid chromatography coupled to isotope ratio mass spectrometry:: A new perspective on honey adulteration detection

A new procedure to determine individual sugar (sucrose, glucose, and fructose) C-13 isotope ratios, using liquid chromatography-isotope ratio mass spectrometry (HPLC-IRMS), has been developed to improve isotopic methods devoted to the study of honey authenticity. For this purpose 79 commercial honey samples from various origins were analyzed. Values of delta C-13(honey) ranged from -14.2 to -27.2%, and delta C-13(protein) ranged from -23.6 to -26.9%. A very strong correlation is observed between the individual sugar C-13 ratios, which are altered in the event of sugar addition, even at low levels. The use of Delta delta C-13 [fruct-glu], Delta delta C-13 [fruct-suc], and Delta delta C-13 [gluc-suc] systematic differences as an authenticity criterion permits the sugar addition [C-3, beet sugar; or C-4, cane sugar, cane syrup, isoglucose syrup, and high-fructose corn syrup (HFCS)] to be reliably detected (DL = 1-10%). The new procedure has advantages over existing methods in terms of analysis time and sensitivity. In addition, it is the first isotopic method developed that allows beet sugar addition detection.