Food irradiation is a common preservation method that is used in many countries. The ability to identify irradiated food is important for assuring compliance with regulatory policies, such as food labeling requirements, and for informed consumer choice. There is thus a significant demand for analytical methods of high sensitivity and selectivity to identify irradiated food, especially for foods subjected to low-dose irradiation and for processed or composite foods that contain small quantities of irradiated ingredients. 2-Alkylcyclobutanones (2-ACBs) are uniquely formed during food irradiation and have been adopted by the European Committee for Standardization as signature biomarkers for the identification of irradiated foods. We now report the development of a novel assay for quantification of 2-ACBs in γ-irradiated food by liquid extraction of fat content followed by precolumn derivatization and liquid chromatography-tandem mass spectrometric (LC-MS/MS) detection. Precolumn derivatization with hydroxylamine introduced a polar functional group into the otherwise nonpolar 2-ACBs, which greatly enhanced ESI-MS response. The method was validated for extraction efficiency, precision, accuracy, and detection limit. In comparison with the current GC-MS based European official method (EN1785:2003) for 2-ACBs determination, our new LC-MS/MS method offers a more efficient sample processing protocol with reduced solvent consumption. More importantly, the combination of chemical derivatization and LC-MS/MS detection significantly enhanced the analytical sensitivity of the method, which allows confident identification of food irradiated with as little as 10 Gy. To the best of our knowledge, this is the first report of 2-ACB determination by LC-MS/MS and the first analytical method allowing confident identification of irradiated food at dosage of down to 10 Gy.

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2-Alkylcyclobutanones (2-ACBs) are uniquely formed when triglycerides-containing food products are exposed to ionizing radiation. Thus, 2-ACBs have been used as marker molecules to identify irradiated food. Most methods to determine 2-ACBs involve mass spectrometric detection after chromatographic separation. The spectrofluorometer is rarely used to determine 2-ACBs because these molecules do not fluoresce. In this study, we developed an ultra-performance liquid chromatography (UPLC) method to determine 2-ACBs. 2-ACBs were converted into fluorophores after reacting with 1-naphthalenyl hydrazine to facilitate their sensitive and selective detection using a fluorescence detector (FLD). Analysis of 2-ACBs using our developed UPLC-FLD method allows sensitive determination of 2-ACBs at a detection limit of 2 ng 2-ACBs per g of fat (30 pg/injection), which is significantly lower than that of existing analytical methods. After validation for trueness and precision, the method was applied to γ-irradiated chicken samples to determine their 2-ACB content. Comparative studies employing liquid chromatography-tandem mass spectrometric method revealed no systematic difference between the two methods, thereby demonstrating that the proposed UPLC-FLD method can be suitably used to determine 2-ACBs in irradiated foodstuffs. Graphical Abstract Determination of radiation-induced food-borne 2-dodecylcyclobutanone and 2-tetradecylcyclobutanone by combining 1-naphthalenyl hydrazine derivatization and ultra-performance liquid chromatography with fluorescence detection.