Determination of carbon isotope ratios for honey samples by means of a liquid chromatography/isotope ratio mass spectrometry system coupled with a post‐column pump

• Published in: Rapid communications in mass spectrometry 2018-08, Vol.32 (15), p.1271-1279
• Main Authors: Kawashima, Hiroto, Suto, Momoka, Suto, Nana
• Format: Article
• Language: English
• Subjects: Caffeine; Carbon dioxide; Carbon isotopes; Chromatography; Disaccharides; Flow velocity; Fructose; Glucose; Honey; Isotope ratios; Isotopes; Mass spectrometry; Organic acids; Pesticides; Scientific imaging; Sodium persulfate; Spectroscopy
• ISSN: 0951-4198; 1097-0231
• DOI: 10.1002/rcm.8170

Rationale Liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) has been used to authenticate and trace products such as honey, wine, and lemon juice, and compounds such as caffeine and pesticides. However, LC/IRMS has several disadvantages, including the high cost of the CO2 membrane and blocking by solidified sodium persulfate. Here, we developed an improved system for determining carbon isotope ratios using LC/IRMS. Methods The main improvement was the use of a post‐column pump. Using the improved system, we determined δ13C values for glucose with high accuracy and precision (0.1‰ and 0.1‰, respectively; n = 3). The glucose, fructose, disaccharide, trisaccharide, and organic acid constituents of honey samples were analyzed using LC/IRMS. Results The δ13C values for glucose, fructose, disaccharides, trisaccharides, and organic acids ranged from −27.0 to −24.2‰, −26.8 to −24.0‰, −28.8 to −24.0‰, −27.8 to −22.8‰, and − 30.6 to −27.4‰, respectively. The analysis time was a third to a half of that required for analysis by previously reported methods. Conclusions The column flow rate could be arbitrarily adjusted with the post‐column pump. We applied the improved method to 26 commercial honey samples. Our results can be expected to be useful for other researchers who use LC/IRMS.