Preliminary investigation on three extraction methods of phenolic compounds from olive mill wastewater

The main by-product of olive oil processing is a mill wastewater, which is characterized by high concentration of phenolic substances (currently polyphenols). In this paper, the isolation of such substances from olive mill wastewater, by different methods, was tested and discussed. Particularly, solid-phase extraction and liquid–liquid methods were compared, in which two different procedures are illustrated for the last method. Quantification of phenolic and o-diphenolic substances in the extracts was performed by the traditional Folin–Ciocalteau method and the sodium molybdate reaction, respectively. The evaluation of their effectiveness was based on thin layer chromatography (TLC). Furthermore, the traces relative to phenolic compounds in the extracts were carried and the tentative identification of six peaks was carried out by HPLC with diode array (DAD) and mass spectrometric detection (MSD).