Application of derivative spectrophotometry to determination of flavonoid mixtures.

Derivative spectrophotometry (DS) was applied to determination of flavonols and a flavon in two-compound mixtures by means of 'zero-crossing' technique. Selected mixtures were, quercetin-kaempferol, quercetin-myricetin and quercetin-luteolin. The developed method was used as a complementary technique to a HPLC system, which does not separate quercetin and luteolin.