Quantification of Nε-carboxymethyl-lysine in selected chocolate-flavoured drink mixes using high-performance liquid chromatography–linear ion trap tandem mass spectrometry

Nε-carboxymethyl-lysine (CML) is considered to be an important marker of the Maillard reaction. In the present investigation a liquid chromatography coupled to ion trap tandem mass spectrometry has been developed for the analysis of CML and lysine in drink mixes. To ensure the best specificity of the method, porous graphitic carbon packing material was used for the chromatographic separation and two transition reactions were recorded per analyte. With the stable-isotope dilution technique employed in this method the recovery ranged from 100% to 111.4% for CML. All other performance characteristics tested were also satisfactory. The method was applied to the analysis of chocolate-flavoured drink mixes after sodium borohydride reduction and acid hydrolysis. In this food category, CML content varied from 8.1 to 131.9 μg/g powder or 95 to 3527 μg/g protein. Among the food items analysed by different laboratories chocolate-flavoured drink mixes appear to have one of the highest CML contents.