Determination of lactones in wines by headspace solid-phase microextraction and gas chromatography coupled with mass spectrometry.

Application of headspace solid-phase microextraction (HS-SPME) coupled with high-resolution gas chromatographic (HRGC) analysis was studied for determining lactones in wines. Six different SPME fibers were tested, and the influence of different factors such as temperature and time of desorption, ionic strength, time of extraction, content of sugar, ethanol, tannins and anthocyanins, and pH and influence of SO2 were studied. The proposed HS-SPME-GC method is an appropriate technique for the quantitative analysis of γ-butyrolactone, γ-hexalactone, trans-whiskey lactone, γ-octalactone, cis-whiskey lactone, γ-nonalactone, γ-decalactone, δ-decalactone, and γ-undecalactone in wines. Method reproducibility and repeatability ranged between 0.6 and 5.2% for all compounds. Detection limit for γ-butyrolactone was 0.17 mg/L and a few µg/L for the rest of the compounds. The optimized method has been applied to several wine samples.

Optimisation of a solid-phase microextraction procedure for the determination of triazines in water with gas chromatography-mass spectrometry detection.

A procedure based on solid-phase microextraction (SPME) and gas chromatography-mass spectrometry, operating in the chemical ionisation mode, was developed and optimised in order to determine 10 triazines in water samples. Five different SPME fibers available for analysis [polydimethylsiloxane (PDMS) 100 microm, polyacrylate (PA) 80 microm, PDMS-divinylbenzene (DVB) 65 microm, Carbowax (CW)-DVB 65 microm, and Carboxen (CAR)-PDMS 75 microm] were tested, and PDMS-DVB was selected. To enhance the sensitivity of the SPME, variables affecting adsorption and desorption steps such as temperature, time, pH and ionic strength of the solution were optimised. Detection limits obtained were ranged between 2 and 17 ng l(-1), and precision values were below 8% for the selected PDMS-DVB fiber. The optimised method was applied to real water samples and no triazines were detected.

Selenium and mercury concentrations in sweet and dry bottled wines from the Canary Islands, Spain.

The concentrations of selenium and mercury were determined by atomic absorption spectrophotometry in sweet and dry bottled wines from the Canary Islands, Spain. The concentrations of mercury ranged from 2.6 to 4.9 microg x l(-1) for sweet wines, and from 1.5 to 2.6 microg x l(-1) for dry wines, differences (p < 0.05) being observed according to the island of production and type of wine, but not with respect to vintage. The concentration of selenium varied between 1.0 and 2.0 microg x l(-1) for sweet wines, and between 0.6 and 1.6 microg x l(-1) for dry wines. Differences were found in the mean concentrations according to the type of wine. Dry wines produced in La Palma presented a higher (p < 0.05) mean content than those observed in the wines of El Hierro and Lanzarote.

Determination of esters in dry and sweet white wines by headspace solid-phase microextraction and gas chromatography.

Headspace solid-phase microextraction (HS-SPME) was studied for the high-resolution gas chromatographic (HRGC) analysis of esters in wines. Five different SPME fibers were tested and the influence of different factors such as temperature and time of desorption, extraction time, extraction technique, stirring, sample and vial volume, sugar and ethanol content were studied and optimised using model solutions. The proposed HS-SPME-GC method is an appropriate technique for the quantitative analysis of esters in dry and sweet white wines.

Comparison of different coatings in solid-phase microextraction for the determination of organochlorine pesticides in ground water.

A solid-phase microextraction (SPME) procedure using three commercialised fibers (Carbowax-divinylbenzene, Carboxen-polydimethylsiloxane and divinylbenzene-Carboxen-polydimethylsiloxane) is presented for the determination of a selected group of organochlorine compounds in water samples. The extraction performances of these compounds were compared using fibers with two and three coatings. The optimal experimental procedures for the adsorption and desorption of pesticides were determined. The limits of detection with the divinylbenzene-Carboxen-polydimethylsiloxane fiber at levels below ng l(-1) were similar or lower than values presented in the literature for several of these compounds using polydimethylsiloxane fiber. The advantages of using this fiber, such as no salt addition, are discussed. Finally, the optimised procedures were applied successfully for the determination of these compounds in polluted ground water samples.

[Algorithm for automatic endocardium identification in digital echocardiography image sequences]. / Algorithmus zur automatischen Endokarderkennung in digitalen echokardiographischen Bildsequenzen.

The present paper describes an automated procedure for the detection of left ventricular internal wall edges in digital echocardiographic image sequences. The proposed procedure is divided into three steps and programmed in C/UNIX. It includes the use of a specially designed, application-specific adaptive spatio-temporal filter for noise reduction in echocardiographic image sequences, local 3-D histogram equalization for augmented contrast, and segmentation of the left ventricle using a regional growth method. When designing the adaptive spatio-temporal filter, we took into account the fact that the background noise is correlated in tangential orientation due to beam deflection at interfaces characterized by a large impedance "jump". Using the specially designed filter, the background noise is successfully reduced without degrading the ventricular contours. The simulation results presented highlight the performance of the proposed method in an exemplary manner.

Evaluation of Osilinus attratus as a bioindicator organism to monitor oil pollution in the Canary Islands.

Concentrations of n-alkanes and PAHs in the visceral mass of the marine winkle Osilinus attratus taken from three locations on the southeast coast of Tenerife (Canary Islands, Spain) over a two-year period, were evaluated at monthly intervals in order to assess if this small marine winkle may be used as bioindicador organism. Factor analysis and cluster analysis were applied in order to determine if it was possible to relate sampling areas to potential sources of petroleum contamination.

[Tenth anniversary of chapter Falcon's: notes for the history of the Venezuelan Association for the Advancement of Science (AsoVAC)]. / A diez años de la creación del capítulo Falcón: apuntes para una historia de la Asociación Venezolana para el Avance de la Ciencia (AsoVAC).

Chapter Falcón of the Venezuelan Association for the Advancement of Science (AsoVAC) was chartered in 1984. In this essay we outline and analyze the circumstances and elements that made possible the establishment of this chapter. The key factors probably were a tight relation with Universidad Nacional Experimental Francisco de Miranda (UNEFM), which allowed to advance several common projects; the selection of realistic projects that could be "read" as organizational muscle; setting of goals that could be achieved with the resources at hand; and taking advantage of some of the psychological traits of Falcón State inhabitants. This chapter's future is pondered under the light of the unusual responsibilities that it will face during this year: mainly the organization of the AsoVAC annual convention, which will be held in Falcón for the first time.