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.