2.3. Sample preparation
2.3.1. Extraction procedure
Approximately 1 g of sample was accurately weighed in a 10 mL
capped test tube. A 0.5 mL aliquot of the internal standard CA stock
solution, 0.5 mL hydrochloric acid–water (1:1, v/v) and 5 mL
diethyl ether were then added successively. The mixture was then
sonicated for 1 min before being allowed to separate into layers.
The upper ether layer was quantitatively transferred by an injector
to another 10 mL capped test tube.