Stir bar sorptive extraction coupled with GC/MS applied to honey: optimization of method and comparative study with headspace extraction techniques

The stir bar sorptive extraction (SBSE) techniques, coupled with gas chromatography–mass spectrometry, were successfully applied to the study of Eucalyptus honey’s for the determination of volatile organic compounds (VOCs). An optimization of the extraction method was carried out and the variables, NaCl concentration (used as matrix modifier), and the concentration of honey solution were studied targeting the whole VOCs composition. After the evaluation of the experiments, the best condition for the extraction of honey volatile components was 2 mol/L of NaCl and the more concentrated honey solution (0.5 g of honey per mL of water). Additionally, the results were compared with those obtained by two headspace (HS) techniques, namely solid-phase microextraction (SPME) and dynamic headspace (DHS). SBSE volatiles differ qualitatively and quantitatively from those obtained by the SPME and DHS methods. In any event, the chemical composition of Eucalyptus honey volatiles extracted by all three techniques shows the presence of some typical floral markers. Our results confirm a general trend reported in the literature, which show the higher sensitivity of SBSE in the extraction of less volatile compounds in comparison with HS methods

Variation of the chemical composition of waste cooking oils upon bentonite filtration

The chemical composition and the color of samples of waste cooking oils (WCOs) were determined prior to and after filtration on two different pads of bentonite differing in particle size. The volatile fraction was monitored by headspace solid-phase microextraction (HS-SPME) coupled with gas-chromatography, while the variation of the composition of the main components was analyzed by 1H NMR. Both techniques allowed the detection of some decomposition products, such as polymers, terpenes, and derivatives of the Maillard process. The analysis of the chemical composition prior to and after bentonite treatment revealed a tendency for the clays to retain specific chemical groups (such as carboxylic acids or double bonds), independent of their particle size. A pair comparison test was conducted in order to detect the sensory differences of the intensity of aroma between the WCO treated with the two different bentonites. In addition, characterization of the bentonite by means of powder X-ray diffraction (XRD) and thermogravimetric measurements (TG) was performed