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Detection of nitrate and nitrite in different seafood

Chiesa, Luca, Arioli, Francesco, Pavlovic, Radmila, Villa, Roberto, Panseri, Sara
Food chemistry 2019 v.288 pp. 361-367
fish, hydrogen peroxide, ion exchange chromatography, mass spectrometry, nitrates, nitrites, oxidation, seafoods, shrimp, smoked salmon
High-performance ion-exchange chromatography with suppressed conductivity (HPIEC-SCD) was validated for the determination of nitrite (NO2−) and nitrate (NO3−) in the edible part of diverse seafood species. Samples analyzed by HPIEC-SCD that were devoid of nitrite and nitrate were subjected to HRMS using a Q-exactive Orbitrap platform. As NO2− is not detectable in Q-Exactive Orbitrap, it was necessary to perform the oxidation of NO2− to NO3−. Accordingly, suitability of NO2− oxidation by H2O2 as a part of sample preparation for HPIEC-HRMS was elaborated. The difference in the concentration of NO3− before and after H2O2 treatment was used for the evaluation of eventual NO2− presence. The edible part of 53 fish, shrimp and bivalve species presented significant differences in NO3− levels especially between farmed (median = 44 μg/g) and wild species (median = 16 μg/g). The highest concentration of NO3− was found in smoked salmon samples (median = 60 μg/g) while NO2− was not revealed in any of the samples studied.