An HPLC-coulometric electrode array detection (CEAD) based method for the determination
of protocatechuic acid, chlorogenic acid, rutin (quercetin-3-O-rutinoside), nicotiflorin (kaempferol-3-Orutinoside)
and quercetin in elderberry juice was developed. Sample work up for the determination of
phenolic acids included solid phase extraction (SPE). For the analysis of flavonoids, simple dilution and
centrifugation steps were sufficient. The compounds were separated isocratically on the same reversed
phase column using two different mobile phases to prevent long retention times and tailing of the aglycone
peaks. The analytes were then detected at twelve coulometric cells. The current/voltage curves contributed
to compound identification and to verification of the peak purity of the separated compounds.
Additionally, LC-ESI-MS in the negative ion scan mode was applied for qualitative analysis. Quantification
of the compounds was carried out by standard addition method. The content in elderberry juice varied
between 785 mg/l for rutin and 2.8 mg/l for quercetin. The presented rapid and reliable method can be
used to differentiate between elderberry juices of different origins. Coulometric electrode array detection
was applied for the first time for the determination of these compounds in elderberry juice.
Dedicated to em. O. Univ. Prof. Dr. Adolf Neckel on the occasion of his 90th birthday.
Keywords: Phenolic compounds, identification, quantitation, HPLC-CEAD, HPLC-ESI-MS, elderberry juice.
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