Development of a High-Performance Liquid Chromatography-Fluorescence Method for Determination of Ethoxyquin and Its Dimer in Antarctic Krill Powder

Ethoxyquin (EQ) is a quinolone-based synthetic antioxidant that prevents lipid peroxidation and is added to consumer products and animal feeds as a preservative. Importantly, EQ is added to Antarctic krill products, and this can pose health hazards to consumers, and monitoring EQ levels in these products is an important means to ensure consumer safety. Thus, we established a method for the simultaneous analytical determination of EQ and its primary metabolite the ethoxyquin dimer (EQDM). The residual EQ and EQDM in Antarctic krill powder (AKP) were extracted with sodium carbonate solution and acetone and then extracted with n-hexane by liquid–liquid extraction. After purification by neutral alumina solid-phase extraction column and primary secondary amine, the analytes were determined by high-performance liquid chromatography (HPLC) with fluorescence detection. The calibration curves were linear in a range of 0.005–2 µg/mL for EQ and 0.05–20 µg/mL for EQDM with correlation coefficients >0.999. The recoveries ranged from 78.8% to 101% at three spiked levels. The intra- and inter-day relative standard deviations were <15%. The limits of detection were 3 and 30 µg/kg, and the limits of quantification were 10 and 100 µg/kg for EQ and EQDM, respectively. The proposed method was sensitive, accurate, easy to operate, and economical and is suitable for the determination of EQ and EQDM in AKP.