Determination of ethoxyquin and two of its oxidation products in fish meal by gas chromatography

Abstract

A gas chromatographic procedure for the determination of the antioxidant ethoxyquin (EQ) in fish meals using methoxyquin as internal standard is described. Recoveries of EQ from spiked meals ranged from 95 to 107%. Comparison of the results obtained with the proposed method and those given by a method applied on a routine basis using chromatography on alumina shows that the results obtained with the latter method should, on average, be corrected by multiplication by a factor of 1.1 when dealing with meals having EQ contents above approximately 30 mg kg^–1. Meals with EQ contents of less than 30 mg kg^–1 yield values by chromatography on alumina which are too high. In addition, gas chromatographic methods for the determination of two oxidation products of EQ, viz., a dimeric oxidative coupling product and a quinolone, are described. The progressive decrease of EQ and the simultaneous formation of the two oxidation products on storage of five fish meals is demonstrated.