Analysis of 2‑Alkylcyclobutanones in Cashew Nut, Nutmeg, Apricot Kernel, and Pine Nut Samples: Re-evaluating the Uniqueness of 2‑Alkylcyclobutanones for Irradiated Food Identification

2-Alkylcyclobutanones (2-ACBs) have long been considered as unique radiolytic products that can be used as indicators for irradiated food identification. A recent report on the natural existence of 2-ACB in non-irradiated nutmeg and cashew nut samples aroused worldwide concern because it contradicts the general belief that 2-ACBs are specific to irradiated food. The goal of this study is to test the natural existence of 2-ACBs in nut samples using our newly developed liquid chromatography–tandem mass spectrometry (LC–MS/MS) method with enhanced analytical sensitivity and selectivity ( Ye Y. ; Liu H. ; Horvatovich P. ; Chan W. Liquid chromatography–electrospray ionization tandem mass spectrometric analysis of 2-alkylcyclobutanones in irradiated chicken by precolumn derivatization with hydroxylamine. J. Agric. Food Chem. 2013, 61, 5758−5763 ). The validated method was applied to identify 2-dodecylcyclobutanone (2-DCB) and 2-tetradecylcyclobutanone (2-TCB) in nutmeg, cashew nut, pine nut, and apricot kernel samples (n = 22) of different origins. Our study reveals that 2-DCB and 2-TCB either do not exist naturally or exist at concentrations below the detection limit of the existing method. Thus, 2-DCB and 2-TCB are still valid to be used as biomarkers for identifying irradiated food.