Headspace-solid phase microextraction-gas chromatography as a tool to define an index that establishes the retention capacity of the wine polymeric fraction towards ethyl esters

A headspace-solid phase microextraction followed by gas chromatographic analysis (HS-SPME-GC) was developed to be applied in the study of the interactions between the wine polymeric fraction and the ethyl esters: ethyl hexanoate, ethyl octanoate, and ethyl decanoate. Wine models (WM) were prepared with 10% (v/v) aqueous ethanol at pH 3.5 with distinct wine polymeric concentrations prepared from white wine of Vitis vinifera L. var. Fern?o-Pires: 1.0 g L(-1) (PWM1), with a polymeric concentration approaching the real one in wine; 10.0 g L(-1) (PWM10); and 30.0 g L(-1) (PWM30), saturated with polymeric fraction. A reference wine model (RWM) was prepared without polymeric fraction. Each volatile compound (4.0 mg L(-1)) was added separately to the RWM and to the WM with the three levels of polymeric material (PWM). From the retention index (RI) calculated for each compound using the formula: [RI = 1 - (C(RWM) - C(PWM))/C(RWM)], where C(RWM) is the concentration of the compound in the RWM and C(PWM) is the concentration of the compound in the given PWM, the retention capacity of each wine polymeric fraction towards the three esters was established. The higher retention indexes were observed for ethyl decanoate, the more hydrophobic compound, and for the PWM with higher concentration. Furthermore, this study also suggested that the retained compounds are dosed to the headspace, which may promote the perception of their aroma for a longer period of time.     

Process for detecting <Emphasis Type="Italic">Helicobacter pylori</Emphasis> using aliphatic amides

Helicobacter pylori diagnosis is fundamental in the management of gastrointestinal pathologies, whose current clinical guidelines support a non-invasive ‘test-and-treat’ strategy. As such, the present work reports the basis of a new, low-cost, specific breath test based on the detection of volatile carboxylic acids resulting from the hydrolysis of short-chain aliphatic amides by H. pylori amidases. Propionamide and butyramide, which are metabolized by amidases to propionic and butyric acids, were elected for this study. Conditions for the extraction of these acids from a vapour phase were optimized concerning the use of solid-phase microextraction (SPME) followed by gas chromatography–quadrupole mass spectrometry (GC–qMS) analysis. SPME–GC–qMS was then used to detect the acids released into a vapour phase upon incubation of a H. pylori reference strain J99 or a clinical specimen with the amides. These experiments have demonstrated that the administration of less than 9 mg of propionamide and/or butyramide to H. pylori cultures, in loads recognized to cause infection (10⁶–10⁹ cells), resulted in the formation of detectable and/or quantifiable amounts of propionic and/or butyric acids after 30 min incubation. As such, propionic and butyric acids can be used as biomarkers for H. pylori upon incubation with the corresponding amides. SPME–GC–qMS was also used to verify the hepatic stability of the acids. These experiments were conducted in mouse liver cells and revealed no signs of metabolization that could compromise their bioavailability in future in vivo assays. Moreover, SPME–GC–qMS permitted the detection of both acids in amounts as low as 0.8 μg in systems mimicking exhaled breath, demonstrating the sensitivity of the method for these compounds.     

On the low-lying excited states of sym-triazine-based herbicides.

We report a joint computational and luminescence study on the low-lying excited states of sym-triazines, namely, 1,3,5-triazine (1) and the ubiquitous herbicides atrazine [6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine (2)] and ametryn [6-methylthio-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine (3)]. Geometrical structures, energetics, and transition and state properties of I and 2 were computed at the TD-DFT, CASSCF, and CASPT2 levels of theory. The fluorescence and phosphorescence emission spectra, lifetimes, and fluorescence quantum yields were measured for the three compounds, and from these, the energies of the lowest excited states and their corresponding radiative rates were determined. The predictions from CASPT2 calculations are in good agreement with the experimental results obtained from the luminescence studies and allow the interpretation of different absorption and emission features.