Metabolites of ethoxyquin (EQ, 1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) in the urine of sheep and rats were separated and identified by gas chromatography-mass spectrometry (GC-MS). Sheep were given diets containing EQ or EQ.HCl (0.5% of total diet) and urine samples were collected for the first 24 h and for another 24-h period after 12 d of feeding. Rats were given EQ/corn oil (0.08 g EQ/d/rat) orally for 7 d and urine samples were collected at ambient temperature for a 24-h period following 6 d of dosing. The urine samples were extracted with ethyl acetate at pH 5, and the concentrated extracts were analyzed by GC-MS. Ethoxyquin was identified in all sheep urine samples collected during the first 24 h of feeding, and EQ and hydroxylated EQ were identified in all urine samples collected after 12 d of feeding. In contrast, EQ, hydroxylated EQ, and dihydroxylated EQ were identified in urine collected from rats fed EQ for 7 d.

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