Grape seed flavan-3-ols are highly to moderate polar species,
thus they are usually analysed by reverse-phase HPLC (RP-HPLC)
(Santos-Buelga et al., 2003), using a C18 bonded stationary phase
and gradient elution. Elutions of 60–90 min are carried out mostly
when purified samples are assessed (Bartolome´ et al., 1996).
Nevertheless, for achieving separation of most of the monomeric
and dimeric flavan-3-ols with direct injection of the sample, longer
elutions (90–120 min) and slower gradients (up to 15–20% of the
less polar mobile phase component) are preferred Some oligomers with degree of polymerisation of up to 4 and
degree of galloylation of up to 2 have been separated in this way,
but the increasing number of species and the decreasing levels of
their amounts with the increase of their molecular masses usually
lead to their overlapping and hiding with/in other species. An
additional problem is the presence of highly polymerised and
complex, chromatographically non-separable procyanidins, which
elute together under the resolved peaks as a broad baseline drift
(‘‘background hump’’) and which require the introduction of
previous purification procedures, such as liquid-liquid or solidphase
extraction
Grape seed flavan-3-ols are highly to moderate polar species,thus they are usually analysed by reverse-phase HPLC (RP-HPLC)(Santos-Buelga et al., 2003), using a C18 bonded stationary phaseand gradient elution. Elutions of 60–90 min are carried out mostlywhen purified samples are assessed (Bartolome´ et al., 1996).Nevertheless, for achieving separation of most of the monomericand dimeric flavan-3-ols with direct injection of the sample, longerelutions (90–120 min) and slower gradients (up to 15–20% of theless polar mobile phase component) are preferred Some oligomers with degree of polymerisation of up to 4 anddegree of galloylation of up to 2 have been separated in this way,but the increasing number of species and the decreasing levels oftheir amounts with the increase of their molecular masses usuallylead to their overlapping and hiding with/in other species. Anadditional problem is the presence of highly polymerised andcomplex, chromatographically non-separable procyanidins, whichelute together under the resolved peaks as a broad baseline drift(‘‘background hump’’) and which require the introduction ofprevious purification procedures, such as liquid-liquid or solidphaseextraction
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