P. He et Rg. Ackman, HPLC determination of ethoxyquin and its major oxidation products in freshand stored fish meals and fish feeds, J SCI FOOD, 80(1), 2000, pp. 10-16
A new method was developed to determine 1,2-dihydro-6-ethoxy-2,2,4-trimethy
lquinoline (EQ, ethoxyquin), 2,6-dihydro-2,2,4-trimethyl-6-quinolone (QI) a
nd 1,8'-di(1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) (DM) in fish meal
s or fish feeds, QI and DM being the oxidation products of EQ. The sample w
as first extracted with hexane. After the removal of hexane the three analy
tes were extracted from the resulting oil with acetonitrile and determined
by C-18 reverse phase highperformance liquid chromatography with a UV detec
tor set at lambda=280nm. The mobile phase was acetonitrile-0.01 M ammonium
acetate (80:20 v/v). The recoveries for EQ, QI and DM from the samples spik
ed at different levels varied in the ranges 90-100 per cent, 75-85 per cent
and 90-100 per cent respectively. At room temperature, QI and DM were the
major oxidation products of EQ in stored fish meals and fish feeds. Loss of
EQ from fish meals is faster than that from feeds, resulting in relatively
higher accumulations of QI and DM in the fish meals. Both QI and DM, espec
ially the former, were not stable during storage of either and could be fur
ther oxidised to unidentified compounds. The residue levels of these two co
mpounds were thus unpredictable during storage intervals. When the storage
temperature was increased to 50 degrees C, EQ disappeared more rapidly, but
neither QI nor DM accumulated. (C) 2000 Society of Chemical Industry.