Determination of Ethoxyquin by High-Performance Liquid Chromatography with Fluorescence Detection and Its Application to the Survey of Residues in Food Products of Animal Origin

An analytical method using HPLC with fluorescence detection (HPLC-FL) has been developed and applied for the survey of residue levels of ethoxyquin in a variety of food products of animal origin. HPLC was performed using a silica octadecylsilane column, butylhydroxytolueneacetonitrilewater (0.05 + 800 + 200, v/v/v) mobile phase, and detection at excitation and emission wavelengths of 370 and 415 nm, respectively. HPLC/MS was used to confirm whether a chromatographic peak was ethoxyquin. The LOQ of the foods was 0.01 µg/g, except for pig fat and cow's milk, and the RSD (n = 6) at 0.1 µg/mL of the standard solution was 1.12. The accuracy of the calculated data of the standard solution was within the range of 94.0 to 101.2. Recoveries of ethoxyquin from the food products of cattle, pigs, chickens, and salmon were more than 71.0 with an RSD of <9.3, except for chicken liver at different concentration levels, including the lower LOQ, the maximum residue limit (MRL), and in some tissues, twice the MRL. Residue levels of ethoxyquin in 33 commercially available food products of animal origin that were purchased on the west side of the Tokyo metropolitan area were surveyed. Contents of ethoxyquin residues in three chicken fat samples by the HPLC-FL method were 0.08, 0.03, and 0.04 µg/g, all less than the MRL (5 µg/g).