Egg samples were collected at the farm layer immediately after
egg laying and then immediately transported to the laboratory. The
eggs were broken, and the albumen was separated from the yolk
with a household yolk separator. For amine extraction, 3 g of yolk
samples and 3 g of albumen samples were weighed in 50-mL polypropylene
centrifuge tubes, and 7 mL of trichloroacetic acid at
50 g L1 (50 g L1 TCA) was added. The tubes were agitated for
10 min in a Thermolyne type 50800 orbital shaker (Barnstead
Thermolyne, Iowa, USA) at 225 rpm and then centrifuged (12,100g)
at 4 °C for 21 min in a chilled Beckman J2 MC centrifuge (Beckman
Coulter Inc., California, USA). After centrifugation, the supernatant
was filtered through qualitative filter paper. The procedure was
repeated two more times with the addition of 7 mL and 6 mL of
50 g L1 TCA in a total of 20 mL of added acid. The resulting extracts
were stored in 0.5 mL microtubes and frozen at 20 °C for later
derivatization and chromatographic analysis.