Quantitative analysis of mutagenic heterocyclic aromatic amines in cooked meat using liquid chromatography-atmospheric pressure chemical ionisation tandem mass spectrometry

Five mutagenic heterocyclic aromatic amines (HAAs) were quantified from meat extracts, and grilled and pan fried bacon samples using stable isotopically labeled internal standards. These compounds were isolated from the matrices by a tandem solid-phase extraction procedure, followed by separation on reversed-phase liquid chromatography (HPLC) and quantified by atmospheric pressure chemical ionization tandem mass spectrometry (APCIMS- MS). Tandem mass spectrometry (MS-MS) acquisition was done in selected reaction monitoring (SRM) mode to provide a high degree of sensitivity and selectivity for accurate quantification of HAAs. The detection and quantification limits of these HAAs approached 0.015 and 0.045 μg/kg (part- per-billion), respectively, with only 4 g of meat. The HAA levels ranged widely from 0.045 to 45.500 μg/kg, and 2-amino-3,8-dimethylimidazo[4,5- f]quinoxaline (MeIQx) was the predominant HAA found in these samples. The amount of HAAs formed was highly dependent upon the type of meat and method of preparation. An intralaboratory comparison of the extraction procedure showed that estimates of these HAAs obtained by three different individuals at HAA levels below 2 μg/kg were within 5% with coefficients of variation below 19%, indicating the robustness of the analytical method. Moreover, because all of these HAAs from this class of molecules undergo facile cleavage at the N-methylimidazole moiety under collision-induced dissociation (CID) conditions, MS-MS analysis in the constant neutral loss mode of [M+H]⁺-15 enabled the identification of two other HAAs, 2-amino-3- methylimidazo[4,5-f]quinoxaline (IQx) and 2-amino-1,7,9-trimethylimidazo[4,5- g]quinoxaline (7,9-DiMeIgQx), which have rarely been reported in cooked meats. (C) 2000 Elsevier Science B.V.