About 100 mg of finely ground and homogenized
samples were precisely weighed and added to 25 mL of 0.1 N HCl plus 75 mL
of a water:methanol 75:25 solution (v/v).
Extraction efficiency was assessed by preparing PFS
samples with and without the addition
of 2.5 mg/g of analytes and extracting for 5, 10, 15, 20, 25 and 30 min
under stirring by a magnetic device: 20 min was sufficient for
optimal extraction. After extraction, samples were filtered through
a 0.45-mm filter and injected into the chromatographic equipment.