Determination of Nε-(1-Carboxymethyl)-L-Lysine in brewing soy sauce by ultrahigh performance liquid chromatography coupled with tandem mass spectrometry

A method for the determination of Nε-(1-Carboxymethyl)-L-Lysine (CML) in brewing soy sauce was developed using ultrahigh performance liquid chromatography-tandem mass spectrometry. A mixed cation exchange solid phase extraction cartridge was used for purification, while gradient elution of a hydrophilic interaction chromatography column was performed with a 0.1% formic acid aqueous solution-acetonitrile. The adding standard recovery rate of this method ranged from 86.94 to 92.61%, and the relative standard deviation (RSD) was between 3.69 and 6.18%. The limit of detection (LOD) was 0.038 ng/mL, and the limit of quantification was 0.127 ng/mL. The RSD values of the repeatability test and the parallel test were 3.44 and 6.56%, respectively. Using this method, the CML contents determined in eight brewing soy sauce samples were 3.16 ± 0.18 – 15.10 ± 1.19 µg/mL. This method is simple, accurate, sensitive, and precise, and it is an effective method for monitoring the CML content in brewing soy sauce.