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A method was developed for the determination of simple phenolic compounds (PCs) in waste waters from olive oil production plants by liquid chromatography (LC). The sample under examination was acidified to pH 2 to precipitate proteins, acetone was added to eliminate the colloidal fraction, and hexane was used for extraction to eliminate lipidic substances. The solution obtained was filtered and injected into the LC system; the wavelength selected for the spectrophotometric detection was specific for PCs, so that carbohydrates, organic acids, and short-chain free fatty acids did not interfere. Recoveries of 9 PCs spiked to a real sample were 90-100% for concentrations ranging from 20 to 2000 mg/L for each analyte.

A method for the determination of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in fruit juices by high-performance liquid chromatography (HPLC) is described. The method is based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent separation of these derivatives. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives of carbonyl compounds is thus avoided, and direct injection of the sample into the HPLC system is allowed. The procedure offers a high specificity and a detection limit of the order of 10(-8) mol/L. Recoveries of 95-98% are obtained from apple juice spiked at different levels with both analytes. The reproducibility (mean of six determinations) is +/- 2% for F and +/- 3% for HMF.