fragment ions data together with ultraviolet absorbance and retention
time.
C18-columns were used both on UHPLC and on HPLC. The HPLC
method was used for many years in the lab. Now, we tried some
new conditions with different column temperature and solvent
flow rate, and found that 40 C was better suited than 20 C.
Comparing with the HPLC method at 20 C, the better resolution
at 40 C on UHPLC resulted in sharp peaks in the UHPLC chromatogram
for the FOG compounds. Furthermore, rutin and K-grg
were separated on UHPLC under the selected condition, while
there was no separation on HPLC. The contents of these two compounds
were really different in different teas, and green tea samples
contained more K-grg while oolong tea and black tea had
much more rutin. The separation of these two compounds was further
confirmed with the addition of rutin solution to both green tea
and oolong tea samples. It is not clear whether or not this different
content is due to clone, geographic origin or manufacture or to a
combination of all factors.
Other FOG compounds, such as acylated kaempferol glycosides
could be detected on the corresponding mass tracks, however, theconcentration is much lower and not suitable to be quantified with
the current method. This is in principal in tune with the results of
Zhao et al., 2011.
The higher column temperature on UHPLC could not only isolate
rutin and K-grg, but also change the other compounds’ retention
time. Comparing the UHPLC chromatogram with the HPLC
chromatogram in Fig. 2, we could find that the elution order for
M-rut (No. 2) was delayed while Q-gal (No. 11) was ahead. It
was concluded from their peak area and related retention time,
but was not testified due to lack of standards. This might be caused
by the high temperature in UHPLC C18 column. From the HPLC theory,
column temperature could affect both the retention (e) and
control of selectivity (a) and could be used for the optimizing the
resolution of compounds on HPLC (Dolan, 2002). Obviously, the
retention of these FOG compounds was changed due to the higher
40 C column temperature, and some other FOG compounds were
also affected without changing the elution order, such as
compounds No. 15 and 16.
fragment ions data together with ultraviolet absorbance and retentiontime.C18-columns were used both on UHPLC and on HPLC. The HPLCmethod was used for many years in the lab. Now, we tried somenew conditions with different column temperature and solventflow rate, and found that 40 C was better suited than 20 C.Comparing with the HPLC method at 20 C, the better resolutionat 40 C on UHPLC resulted in sharp peaks in the UHPLC chromatogramfor the FOG compounds. Furthermore, rutin and K-grgwere separated on UHPLC under the selected condition, whilethere was no separation on HPLC. The contents of these two compoundswere really different in different teas, and green tea samplescontained more K-grg while oolong tea and black tea hadmuch more rutin. The separation of these two compounds was furtherconfirmed with the addition of rutin solution to both green teaand oolong tea samples. It is not clear whether or not this differentcontent is due to clone, geographic origin or manufacture or to acombination of all factors.Other FOG compounds, such as acylated kaempferol glycosidescould be detected on the corresponding mass tracks, however, theconcentration is much lower and not suitable to be quantified withthe current method. This is in principal in tune with the results ofZhao et al., 2011.The higher column temperature on UHPLC could not only isolaterutin and K-grg, but also change the other compounds’ retentiontime. Comparing the UHPLC chromatogram with the HPLCchromatogram in Fig. 2, we could find that the elution order forM-rut (No. 2) was delayed while Q-gal (No. 11) was ahead. Itwas concluded from their peak area and related retention time,but was not testified due to lack of standards. This might be causedby the high temperature in UHPLC C18 column. From the HPLC theory,column temperature could affect both the retention (e) andcontrol of selectivity (a) and could be used for the optimizing theresolution of compounds on HPLC (Dolan, 2002). Obviously, theretention of these FOG compounds was changed due to the higher40 C column temperature, and some other FOG compounds werealso affected without changing the elution order, such ascompounds No. 15 and 16.
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