Abstract:

The study was conducted to establish an analytical method for measuring 5-vinyl-1,3-oxazolidine-2-thione
(5-VOT) residue in eggs and to apply it on eggs from laying hens fed different levels of rapeseed meal (RSM). A total of 450
30-week-old Lohmann pink-shelled hens were randomly assigned to 3 dietary treatments, including 0%, 17.64% and 29.4%
RSM supplementation for 16 weeks (which was withdrawn during the last 4 weeks). 5-VOT was extracted with acetonitrile,
and then evaporated to dryness with a rotating evaporator under vacuum at 35 ℃. The 5-VOT was re-dissolved in 2 mL of
phosphate buffer (pH 7.0) and purified with 2 mL of n-hexane. Thereafter, the aqueous solution was transferred to a 2 mL
tube and centrifuged for 5 min at 12 000 r/min. The aqueous phase was passed through a 0.45 μm filter for HPLC analysis.
The average recovery rates of 5-VOT ranged from 81.28% to 103.28% with relative standard deviations (RSDs) between
0.75% and 5.17%. The RSDs of repeatability and precision were 2.19% and 0.82%, respectively. The further investigation
showed that 5-VOT concentrations in eggs linearly increased with the increase in either the level of dietary RSM or feeding
time. After 4 weeks of RSM withdrawal, 5-VOT residue was not detected in eggs.

Key words: high performance liquid chromatography, egg, 5-vinyl-1,3-oxazolidine-2-thione