Determination of key flavonoid aglycones by means of nano-LC for the analysis of dietary supplements and food matrices.

A method for the analysis of flavonoids (myricetin,quercetin,naringenin,hesperitin,and kaempferol), with interesting bioactivity,has been developed and validated utilizing nano-LCtechnique. In order to find optimal conditions,capillarycolumns(75 micron id × 10cm) packed with different types of stationaryphases, Kinetex C18 core-shell (2.6 micron particle size),Hydride-based RP-C18(sub-2 micron particle size),and LiChrospher100 RP-18endcapped(5 micron particle size) were evaluated. The method wa svalidated using Hydride-based RP-C18stationaryphase,with sub-2 micron particle size. A good chromatographic performance, expressed in terms of repeatability(RSD,in the range 1.63-4.68% for peak area) column-to-column reproducibility (RSD not higher than 8.01% forpeak area), good linearity and sensitivity was obtained. In particular limit of detection values between 0.07 and 0.31 microg/mL werea chieved with on column focusing technique.The method was applied to th determination of studied flavonoids in dietary supplements as well as in food matrices.The amount of quercetin found in the first analyzed dietary supplement,was in agreement to the labele dcontent.In the othersamples, where the content of flavonoids was not labeled, most of the studied flavonoids were determined in amounts somewhere comparable to those reported in literature.