3.2. Clean-up with polyamide column chromatography
Polyamide column chromatography is a good way for clean-up
of tea samples, and was used to analyze tea samples. The common
method is a two-step of elution, firstly a washing step with pure
water, then with 100% methanol to recover the FOG from the tea
brew. Considering the difference of polarity of catechins and
FOG, we add one more step of elution to separate them. After
trying a series of the organic solvents, 60% methanol was selected
as the best solution.
Table 1 shows that FOG might be effectively recovered with 60%
methanol, and about 96% absorbance was collected in the solution.
The HPLC–MS test had proved that all the FOG are in this part and
the other two parts didn’t contain any FOG compounds. Although
the absorbance at 287 nm is not exclusively due to catechins, we
could deduce when catechins were washed out based on their
absorbance spectra and their retention time on HPLC. From
Table 1 it can be withdrawn that most catechins were eluted by
100% methanol and not by 60% methanol, so that FOG compounds
could be separated from most catechins by this step. This was also
confirmed by analyzing catechins by HPLC in these eluates.
3.2. Clean-up with polyamide column chromatographyPolyamide column chromatography is a good way for clean-upof tea samples, and was used to analyze tea samples. The commonmethod is a two-step of elution, firstly a washing step with purewater, then with 100% methanol to recover the FOG from the teabrew. Considering the difference of polarity of catechins andFOG, we add one more step of elution to separate them. Aftertrying a series of the organic solvents, 60% methanol was selectedas the best solution.Table 1 shows that FOG might be effectively recovered with 60%methanol, and about 96% absorbance was collected in the solution.The HPLC–MS test had proved that all the FOG are in this part andthe other two parts didn’t contain any FOG compounds. Althoughthe absorbance at 287 nm is not exclusively due to catechins, wecould deduce when catechins were washed out based on theirabsorbance spectra and their retention time on HPLC. FromTable 1 it can be withdrawn that most catechins were eluted by100% methanol and not by 60% methanol, so that FOG compoundscould be separated from most catechins by this step. This was alsoconfirmed by analyzing catechins by HPLC in these eluates.
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