were shaken for about 1 minute with 10 mL of n-hexane in a 50 mL centrifuge tube.
Afterwards, 20 mL of water and 200 μL (10 μg mL-1) of an internal standard 13C3-acrylamide
(an added amount corresponding to the concentration of 1000 μg kg-1 matrix) were added and
the mixture was shaken once again for approx. one minute