Determination of the Synthetic Antioxidant Ethoxyquin and Its Metabolites in Fish and Fishery Products Using Liquid Chromatography-Fluorescence Detection and Stable-Isotope Dilution Analysis-Liquid Chromatography-Tandem Mass Spectrometry

Determination of ethoxyquin by ultra-high performance liquid chromatography with tandem mass spectrometry and a Singapore survey of ethoxyquin residues in eggs, egg products and poultry

In this study, an advanced ultra-high performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) method was developed for quantifying ethoxyquin (EQ). The approach employed a distinctive antioxidant added extraction step designed to prevent ethoxyquin decomposition and maintain analytical precision. This method effectively determines residue levels of EQ in eggs, processed egg products, poultry muscle, salmon, and liquid milk. The method was shown to have a limit of quantitation (LOQ) for eggs, milk, salmon, and chicken muscle of 1.5 µg/kg, 1.9 µg/kg, 2.1 µg/kg, and 1.2 µg/kg, respectively. The recoveries of EQ ranged from 79.2% to 107.6%, with a relative standard deviation (RSD) below 8.4%. A surveillance study for the presence of EQ in different types of eggs and poultry muscle available in Singapore was conducted and a total of 140 samples were tested. EQ residues in all samples were found to be below the U.S. Food and Drug Administration (FDA) MRLs of 500 µg/kg. Some samples of salted and preserved eggs from China were detected with higher concentration of EQ.

Seaweed Phenolics as Natural Antioxidants, Aquafeed Additives, Veterinary Treatments and Cross-Linkers for Microencapsulation

Driven by consumer demand and government policies, synthetic additives in aquafeed require substitution with sustainable and natural alternatives. Seaweeds have been shown to be a sustainable marine source of novel bioactive phenolic compounds that can be used in food, animal and aqua feeds, or microencapsulation applications. For example, phlorotannins are a structurally unique polymeric phenolic group exclusively found in brown seaweed that act through multiple antioxidant mechanisms. Seaweed phenolics show high affinities for binding proteins via covalent and non-covalent bonds and can have specific bioactivities due to their structures and associated physicochemical properties. Their ability to act as protein cross-linkers means they can be used to enhance the rheological and mechanical properties of food-grade delivery systems, such as microencapsulation, which is a new area of investigation illustrating the versatility of seaweed phenolics. Here we review how seaweed phenolics can be used in a range of applications, with reference to their bioactivity and structural properties.

Analysis of synthetic antioxidants in salmon silage using QuEChERS extraction method followed by determination by LC-MS/MS; a single-laboratory validation study

A new method was developed and in-house validated to determined ethoxyquin (EQ), butylated hydroxyanisole (BHA) and propyl gallate (PG) in fish silage and fish oil used for production of animal feed. Sample pre-treatment comprises use of QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction and gives extracts for liquid chromatography-triple quadrupole mass spectrometry analysis without matrix interferences. The results allow quantification of the antioxidants in all matrices by using deuterated internal standards and calibration curves made in solvent, as well as establishing low detection limits (0.012-0.015 mg/kg) and quantification limits (0.040-0.050 mg/kg) needed regarding the recent suspension of EQ as feed additive within the European Union. The proposed method was validated in terms of linearity, accuracy (relative error, ±1.4%), precision (RSD, ≤2.7%) and recovery (matrix effect, 97-101%) where all the parameters show acceptable results according to recognized guidelines (including EuraChem) within method validation. Combined expanded measurement uncertainty was estimated with a coverage factor of 2 by including all contributors to analytical variation, showing results of ±15% or better. The combined QuEChERS and LC-MS/MS method was successfully applied to salmon silage samples and their corresponding aqueous and oil fractions.