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.

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Sake is a traditional Japanese alcohol. Nowadays, the consumption for Sake is increasing in worldwide and its popularity is growing. However, there are act of fraudulence by additional brewers’ alcohol and sugar. Therefore, a method is needed to find illegal fraud on label. In this work, we analyzed the δ13C values of the ethanol (δ13Ceth) and glucose (δ13Cglu) in Sake by liquid chromatography combined with isotope ratio mass spectrometry for the first time. Further, we developed the criteria using δ13Ceth and δ13Cglu to check brewers’ alcohol and sugar. In addition, there are some sake categories (Ginjyo and Futsu-shu) allowed to additional brewers’ alcohol up to legally determined percentage. The experimental additions of brewers’ alcohol from a C4 plant were conducted to Junmai, as sake by C3 plants. There was a strong correlation (R = 0.98, P < 0.05) between the percentage of added brewers’ alcohol and the δ13C values. We developed the method using the relationship for calculating percentage of brewers’ alcohol for the first time and estimated the percentage for commercial sake. Further, the price of sake was found to be inversely related to the percentage of brewers’ alcohol in the sake.