Abstract: A method for simultaneous determination of carboxymethyllysine (N-carboxymethyllysine, CML) and carboxyethyllysine (N-carboxyethyllysine, CEL) in salmon by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed in this paper. The chromatographic separation was performed on an ACQUITY UPLC HSS T3 column using a mobile phase composed of 100% acetonitrile and 0.1% formic acid, and the separated analytes were detected by electrospray ionization in the positive ion (ESI+) mode under multiple reaction monitoring (MRM) and quantitated by the isotope internal standard dilution method. Samples were degreased, reduced, and hydrolyzed and the hydrolysate was purified by solid phase extraction on an Oasis MCX column before being injected into the instrument. The average recoveries of the method were 90%–95%, the precision expressed as relative standard deviation (RSD) was less than 5%, the limit of detection (LOD) was 0.032 7 ng/g, and the limit of quantitation (LOQ) was 0.142 2 ng/g. The method was used to detect 21 salmon samples from Norway, Chile and the Faroe Islands, and the obtained data were analyzed by principal component analysis (PCA). The results showed that there were significant differences in CML and CEL contents between different countries and individuals of the same species. This study revealed CEL to be a potential characteristic indicator to distinguish Norway salmon from those from Chilean and the Faroe Islands.

Key words: ultra-high performance liquid chromatography-tandem mass spectrometry; advanced glycation end products; N-carboxymethyllysine; N-carboxyethyllysine; salmon