2.2.3. HCl/MeOH Procedure

The extraction solution was a 30:1 (*v*/*v*) mixture of hydrochloric acid (HCl) in methanol (MeOH). A total of 300 μL of MeOH/HCl solution were added to the sample and the extraction was performed in an ultrasonic bath for 60 min at 60 ◦C, followed by liquidliquid extraction with ethyl acetate (3 × 200 μL). The extract was dried under a gentle stream of nitrogen and dissolved in 200 μL of acetonitrile (ACN) before injection into the chromatographic systems.
