In situ and real-time authentication of Thunnus species by iKnife rapid evaporative ionization mass spectrometry based lipidomics without sample pretreatment.

Tuna adulteration and mislabeling are serious problem worldwide and have caused economic loss and consumer rights violation. In this study, an electrometric knife (iKnife) coupling rapid evaporative ionization mass spectrometry (REIMS) and a multivariate recognition model were developed and employed for in situ and real-time authentication of four tuna species without sample preparation. The results showed that the lipidomic profiles were successfully acquired and the differences in fatty acids and phospholipids were statistically analyzed to be significant (p < 0.05). The model displayed the superb classification accuracy (>93%) and validation (R2(Y) = 0.992, Q2 = 0.986), and the main contributors of m/z 817.64, m/z 809.68, etc. were screened out to be used as potential biomarkers. Based on this technique, the identity of blind tuna samples could be unambiguously authenticated with the results displayed on a monitor screen directly. This study provided a front-line rapid detection method to prove the authenticity of tuna species.