Magnetic fiber headspace solid-phase microextraction of Ferulago angulata volatile components using Preyssler-type polyoxometalate/metal-organic framework/silica aerogel sorbent.

A new hybrid of silica aerogel with a Preyssler-type polyoxometalate and MIL-101(Cr) metal-organic framework was prepared and used as a highly porous fiber coating for headspace solid-phase microextraction of Ferulago angulata volatile components. Applying a permanent magnetic field to the sorbent increased the extraction efficiency for most of the plant's components, up to 5.53 times. Optimization of the extraction parameters was carried out using a GC-MS instrument and by a simplex method. The extraction efficiency of the P5W30/MIL-101(Cr)/silica aerogel fiber exceeded 3.5 times of a mesoporous SBA-15 fiber. The prepared fiber was stable in multiple injections with relative standard deviations of 5.3 to 10.9% for 5 replicates. The proposed method was successfully applied to the extraction and identification of volatile components of some F. angulata samples. According to the results obtained by GC-FID, ß-bourbonene, ß-gurjunene, ß-elemene and cedrenol were the main components of the plant.

Reversed-phase dispersive liquid-liquid microextraction with multivariate optimization for sensitive HPLC determination of tyrosol and hydroxytyrosol in olive oil.

A reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) method coupled to HPLC was developed for the extraction of hydroxytyrosol (HTy) and tyrosol (Ty) from virgin olive oil. In this first application of the RP-DLLME method to non-polar samples, the phenolic compounds were directly extracted into an aqueous micro-drop, which could be injected into a chromatography column without any further pretreatment. A glass test tube with lengthened conical bottom was fitted inside a centrifuge tube in this work for more efficient withdrawal of the sedimented phase with a microsyringe. The volumes of water and ethyl acetate, the pH of water and the centrifuge time as four effective parameters on the extraction were optimized by a central composite design (response surface) method. Five replicated analyses under the optimized conditions (i.e., 0.2 mL ethyl acetate as disperser and 100 µL water at pH 11 as the extraction solvent) resulted in recoveries of 104.3 and 97.6%, and relative standard deviations of 5.75 and 4.57 for HTy and Ty, respectively. The detection limit of the method (3σ) was 0.043 mg L(-1) for HTy and 0.032 mg L(-1) for Ty. The method was successfully applied to the determination of HTy and Ty in five olive oil samples.