For fish sample, 50 ml of acetone was added to 20 g of sample spiked with the surrogate. The sam- ple was homogenized, centrifuged and the super- natant solution was collected. The residue sample was re-homogenized with 50 ml of acetone in the same way. The acetone phase was combined, poured into the l-l round bottom flask after which steam distillation was performed. 300 ml of distillate was collected. This is necessary for 300 ml of distillate because the first 100 ml fraction is acetone. The distillate was poured into a separating funnel, 20 g of NaCl and 20 ml of hexane were added. Analyte was extracted twice with 20 ml of hexane, the organic
phase was combined and then washed with 10 ml of pure water in order to eliminate a small amount of acetone in the hexane phase. The next procedure was performed in a similar way, and continued at the * mark in Fig. 1.