2.4.2. Analysis of phenolic compounds by HPLC
Reverse phase (RP)-HPLC system for the analysis of phenolic
compounds was used, comprising of Shimadzu LC-20AC pumps, a
SPD-M20A diode array detector and a LUNA C-18 column
(4.6 250 mm i.d., 5 lm). The composition of the solvents and
the gradient elution conditions used were described previously
by Bengoechea et al. (1997) and followed by Butsat, Weerapreeyakul,
and Siriamornpun (2009) with some modifications.
The mobile phase consisted of purified water with acetic acid
(pH 2.74) (solvent A) and acetonitrile (solvent B) at a flow rate of
0.8 ml/min. Gradient elution was performed as follows: from 0 to
5 min, linear gradient from 5% to 9% solvent B; from 5 to 15 min,
9% solvent B; from 15 to 22 min, linear gradient from 9% to 11% solvent
B; from 22 to 38 min, linear gradient from 11% to 18% solvent
B; from 38 to 43 min, from 18% to 23% solvent B; from 43 to
44 min, from 23% to 90% solvent B; from 44 to 45 min, linear gradient
from 90% to 80% solvent B; from 45 to 55 min, isocratic at
80% solvent B; from 55 to 60 min, linear gradient from 80 to 5% solvent
B and a re-equilibration period of 5 min with 5% solvent B
used between individual runs. Operating conditions were as follows:
column temperature, 38 C, injection volume, 20 ll, and
UV-diode array detection at 280 nm (hydroxybenzoic acids),
320 nm (hydroxycinnamic acids) and 350 nm (flavonols) at a
flow-rate of 0.8 ml/min. The spectra were recorded from 200 to
600 nm. The phenolic compounds in the samples were identified
by comparing their relative retention times and UV spectra with
those of authentic compounds and were detected using an external
standard method.
2.4.2. Analysis of phenolic compounds by HPLCReverse phase (RP)-HPLC system for the analysis of phenoliccompounds was used, comprising of Shimadzu LC-20AC pumps, aSPD-M20A diode array detector and a LUNA C-18 column(4.6 250 mm i.d., 5 lm). The composition of the solvents andthe gradient elution conditions used were described previouslyby Bengoechea et al. (1997) and followed by Butsat, Weerapreeyakul,and Siriamornpun (2009) with some modifications.The mobile phase consisted of purified water with acetic acid(pH 2.74) (solvent A) and acetonitrile (solvent B) at a flow rate of0.8 ml/min. Gradient elution was performed as follows: from 0 to5 min, linear gradient from 5% to 9% solvent B; from 5 to 15 min,9% solvent B; from 15 to 22 min, linear gradient from 9% to 11% solventB; from 22 to 38 min, linear gradient from 11% to 18% solventB; from 38 to 43 min, from 18% to 23% solvent B; from 43 to44 min, from 23% to 90% solvent B; from 44 to 45 min, linear gradientfrom 90% to 80% solvent B; from 45 to 55 min, isocratic at80% solvent B; from 55 to 60 min, linear gradient from 80 to 5% solventB and a re-equilibration period of 5 min with 5% solvent Bused between individual runs. Operating conditions were as follows:column temperature, 38 C, injection volume, 20 ll, andUV-diode array detection at 280 nm (hydroxybenzoic acids),320 nm (hydroxycinnamic acids) and 350 nm (flavonols) at aflow-rate of 0.8 ml/min. The spectra were recorded from 200 to600 nm. The phenolic compounds in the samples were identifiedby comparing their relative retention times and UV spectra withthose of authentic compounds and were detected using an externalstandard method.
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