Rotanta 460 R, Hettich AG, Bäch, Switzerland). The supernatant was transferred into a 20 mL brownglass head-space vial. Another 10 mL of petroleum ether were added to the sample, and the process was repeated. The supernatant was added to the one taken before, resulting in approx. 12 mL of extract. An aliquot of 10 mL was transferred to a fresh 20 mL brown-glass head-space vial and 2 µL of internal standard mix (Online Resource 1: Table ) were added, equivalent to a concentration between 1 and 3 ng•mL -1 in the final sample. The extract was evaporated to dryness under a gentle stream of nitrogen. Immediately after evaporation, 100 µL of methanol, serving as solubilizer, and 10 mL of salt solution (200 g NaCl in 1 L ultrapure water) were added.