Method for the isolation of citric acid and malic acid in Japanese apricot liqueur for carbon stable isotope analysis

•We developed an isolation procedure for organic acids in Japanese apricot liqueur.•The procedure minimized carbon isotope discrimination of citric and malic acid.•The procedure allows precise δ13C measurements of citric and malic acid.•Our method will help control authenticity of Japanese apricot liqueur.

A method for detecting the undeclared addition of acidic ingredients is required to control the authenticity of Japanese apricot liqueur. We developed an analytical procedure that minimizes carbon isotope discrimination for measurement of the δ13C values of citric and malic acid isolated from Japanese apricot liqueur. Our results demonstrated that freeze-drying is preferable to nitrogen spray-drying, because it does not significantly affect the δ13C values of citric acid and results in smaller isotope discrimination for malic acid. Both 0.1% formic acid and 0.2% phosphoric acid are acceptable HPLC mobile phases for the isolation of citric and malic acid, although the δ13C values of malic acid exhibited relatively large variation compared with citric acid following isolation using either mobile phase. The developed procedure allows precise δ13C measurements of citric and malic acid isolated from Japanese apricot liqueur.