title: Isotope dilution ESI-LC-MS/MS for quantification of free and total Nε-(1-Carboxymethyl)-L-Lysine and free Nε-(1-Carboxyethyl)-L-Lysine: comparison of total Nε-(1-Carboxymethyl)-L-Lysine levels measured with new method to ELISA assay in gruel samples.
abstract: ESI-LC-MS/MS method with isotope dilution and SPE based on cation-exchange was developed for determination of free and total Nε-(1-Carboxymethyl)-L-Lysine (CML) and free Nε-(1-Carboxyethyl)-L-Lysine (CEL). The use of nonafluoropentanoic acid in mobile phase was omitted, SPE recoveries of 82±3% and 91±10% (n=6) for CML and CEL respectively and, calibration curves (R(2)>0.9985) were attained. The method was applied to gruel samples and LoQ for the method was 5 ng/ml, RSD <10% and accuracy was 115%. Total CML levels in the gruel samples varied from 103-408 mg/kg protein. Free CML levels which were 1000 times lower than total CML were three times higher than free CEL levels. CML in a gruel sample was 127±7, 84±9 and 253±28 mg/kg using the current ESI-LC-MS/MS, ELISA and GC-MS respectively. The described method has advantages over ELISA with respect to reproducibility and specificity and over GC-MS with respect to reproducibility.
authors.affiliation: Division of Applied Nutrition and Food Chemistry, Department of Food Technology, Engineering and Nutrition, Lund University, Sweden. eden.tareke@appliednutrition.lth.se
authors.forename: E
authors.initials: E
authors.lastname: Tareke
authors.forename: A
authors.initials: A
authors.lastname: Forslund
authors.forename: C H
authors.initials: CH
authors.lastname: Lindh
authors.forename: C
authors.initials: C
authors.lastname: Fahlgren
authors.forename: E
authors.initials: E
authors.lastname: Östman
mesh_terms: D001628:Beverages / Q000032:analysis*; D002853:Chromatography, Liquid / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D017127:Glycation End Products, Advanced / Q000737:chemistry*; D007553:Isotope Labeling / Q000379:methods*; D008239:Lysine / Q000031:analogs & derivatives* / Q000737:chemistry; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D017127:Glycation End Products, Advanced; C054688:N(6)-(1-carboxyethyl)lysine; C048496:N(6)-carboxymethyllysine; D008239:Lysine
keywords: AGE; CEL; CML; ELISA; Gruel; LC-MS/MS