Analysis of phenolic and flavonoid compounds in juice beverages using high-performance liquid chromatography with...

Analysis of phenolics and flavonoids in juice beverages using reversed-phase HPLC with coulometric array detection is described. Sixteen serial coulometric detectors were used for on-line resolution of co-eluting compounds and generation of voltammetric data. Within each class of compounds, oxidation potential corresponded to specific substitution patterns where: catechol < methoxycatechol < monohydroxyl < methoxyl. Twenty-seven standard compounds were resolved in a 45-min run. The limits of detection were in the low ng/ml range with a linear response range of at least three orders of magnitude. Intra-run retention time variation was < 1% (R.S.D.) and adjacent sensor response ratios varied by < 5% (R.S.D.). The utility of this technique in generating multivariate data for differentiation of juices and juice mixtures is shown.