Olive mill wastewaters: quantitation of the phenolic content and profiling of elenolic acid derivatives using HPLC-DAD and HPLC/MS² with an embedded polar group stationary phase

Abstract

Olive mill wastewaters (OMWs) are important by-products of olive oil production. The wide availability and the forbidding economic costs of OMWs disposal have generated interest in their possible exploitation as a sustainable source of polyphenols. The development and optimisation of improved analytical methods for the detailed characterisation of polyphenol molecular profiles after production and during storage conditions are thus required. A new analytical method based on reverse-phase HPLC separation of polyphenols in OMWs on an embedded-polar group (EPG) stationary phase is proposed as an alternative to conventional C18 columns. The procedure was used for the quantitation of 11 polyphenols, using diode-array detection (DAD), and achieving quantitation limits equal to or lower than 0.1 µg g⁻¹. The same chromatographic set-up, coupled with high resolution tandem mass spectrometry (HPLC/ESI-Q-ToF), allowed us to identify hydroxytyrosyl esters of elenolic acid, whose relative abundance is proposed for monitoring the ageing of OMWs during storage.

Keywords:

• Olive mill wastewaters
• HPLC-DAD
• HPLC/MS2
• RP-Amide
• Polyphenols

Acknowledgements

The authors are grateful to Dr. Francesca Gambineri Laboratori ARCHA srl Unipersonale (Pisa) for the support and the stimulating discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.