In the experiment methanol, and 80% aqueous solution of
methanol were used as extractants. Because of the polar nature
of the analyzed polyphenols higher yields gave 80% aqueous solu-
tion of methanol, in all the cases. Exemplary HPLC chromatograms
of polyphenols isolated by USAE techniques are shown in Fig. 1.
Validation of the methods was performed in terms of accu-
racy, precision LOD, and LOQ. The concentration of all standards
in calibration plots was in range 1–500 ?g mL −1 . The calibration