Between successive extractions, the used thin film was placed in a beaker containing 2mL of methanol and 100 mL of ([Omim][BF4]) ionic liquid, and was treated by sonication for 30 min. Next, the solvent mixture was discarded and thin film was located in a beaker containing only 2 mL of methanol, followed by sonication for 5 min; this procedure was repeated twice.