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.