Simultaneous determination of N ε-(carboxymethyl) lysine and N ε-(carboxyethyl) lysine in cereal foods by LC–MS/MS

Abstract

N e-(carboxymethyl) lysine (CML) and N e-(carboxyethyl) lysine (CEL) are two advanced glycation end products. Few studies have focused on the simultaneous determination of CML and CEL content in foods, especially in Eastern foods. In this study, a stable isotope dilution LC–MS/MS method was developed for the simultaneous determination of CML and CEL in foods. The CML and CEL contents in three cereal foods consumed in China were determined by the developed method. Sample preparation consisted of lyophilization, defatting, grinding, reduction, protein precipitation, acid hydrolysis, and solid-phase extraction. The limit of quantification for CML and CEL was 4 and 3 ng/g, respectively. CML and CEL content in fried dough stick was determined for the first time. CML and CEL contents in fried dough sticks were 28.06–66.69 and 10.67–30.22 μg/g of fried dough sticks, respectively. The highest CML and CEL contents in biscuits were 117.53 and 46.09 μg/g of biscuits, respectively. CML and CEL contents in bread crusts were higher than those in bread crumbs.