Gradient elution was carried out at a flow rate of 1.0 mL min1.
A PDA-100 Photodiode Array Detector was used for UV–vis measurements
and the 3D mode was set at collection rate of 1.0 Hz,
3D wavelength scan range of 250–600 nm, 3D bunch width of
1 nm and band width of 50 nm. The column compartment thermostat
was set at 25 C. The injection volume was set to 25 lL. A gradient
elution was programmed using an acidified aqueous mobile
phase A (2% acetic acid and 5% methanol) and mobile phase B
(2% acetic acid and 88% methanol). The gradient applied was as follows:
(time, solvent B): 0 min, 0%; 10 min, 25%; 25 min, 40%;
30 min, 50%; 35 min, 50%. The identification of phenolic acids in
the samples was achieved by spiking and by comparison of retention
times and maximum UV absorptions with those of standards.
The analytical properties of the chromatographic method for
the determination of 15 phenolic compounds are listed in Table 1.
Typical chromatograms at three different wavelengths (260, 280
and 320 nm) are shown in Fig. 1.