Browsing by Author "Bravo, Manuel A."

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    CHEMOMETRIC OPTIMIZATION OF AN EXTRACTION PROCEDURE USING TARTARIC ACID FOR BUTYLTIN COMPOUNDS FROM SEDIMENT SAMPLES BY GC-PFPD
    (2015) Bravo, Manuel A.; Flores, Marcos; Parra, Sonnia; Quiroz, Waldo; Maxwell, Paulette; Mester, Zoltan
    In this study a simple extraction procedure was developed to minimize the sulfur interferences on the determination of butyltin in sediment samples based on extraction with tartaric acid solution. The optimal conditions were determined using an experimental design methodology and these were achieved using a solution of tartaric acid (0.5 M) with methanol (30 % v/v) for 12 hours in an orbital shaker. This protocol could be followed by a liquid-liquid extraction and this organic phase can be analyzed directly by gas chromatography with pulsed flame photometric detection (GC-PFPD) without any further cleanup due to interferences from elemental sulfur were completely eliminated. The accuracy of the procedure was verified analyzing two reference materials (CRM) (BCR-646, freshwater sediment and PACS-2, marine sediment) and comparing the results to the certified values, the optimized method produced satisfactory results certified values in the CRMs. Finally, harbour sediment samples were analyzed in order to evaluate the suitability of the method for organotin control in complex environmental samples containing high concentrations of sulfur compounds.
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    Global issues in setting legal limits on soil metal contamination: A case study of Chile
    (2022) Tapia-Gatica, Jaime; Selles, Ivan; Bravo, Manuel A.; Tessini, Catherine; Barros-Parada, Wilson; Novoselov, Alexey; Neaman, Alexander
    The establishment of legal limits for soil contamination with trace elements is a global issue that has not yet been resolved. However, the resolution of any global problem begins at the national level. In this vein, we present the case of Chile, the world's leading copper producer, where soil contamination by trace elements in mining areas has been severe. We evaluated the magnitude of the ecological and human health risks from exposure to arsenic (As), copper (Cu), zinc (Zn), and lead (Pb) in soils of the La Ligua and Petorca basins, two important mining areas in Chile. Contrary to what might be expected in soils affected by Cu mining activities, As was identified as the most hazardous element in the studied soils, both in terms of ecological and human health risks. On the other hand, Chile does not currently have specific legislation establishing legal limits on soil contamination with trace elements. Since Chile is geochemically similar to New Zealand, Mexico, and Italy, we used the limits of these three countries as benchmarks. We determined the background concentrations of As, Cu, Zn, and Pb in the soils of the two river basins under study and found that they tend to exceed the limits established by foreign laws. We also found that the differences in background elemental concentrations in the studied soils were primarily due to the varied lithology of soil-forming rocks. This means that absolute "one-limit-fits-all" values of element concentrations may not be adequate to regulate the level of soil contamination in areas affected by mining. As a fundamental first step, it is necessary to establish background soil concentrations of trace elements in each river basin in Chile. It is clear that Chile urgently needs to move from rubber-stamping foreign laws to the development of national legislation on soil metal contamination.
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    hr Hydrophobic deep eutectic solvent as extractant phase for determining six carcinogenic polycyclic aromatic hydrocarbons in tea and coffee infusion samples
    (2023) Mesias-Salazar, Angela; Rebolledo-Robles, Kevin; Salazar-Gonzalez, Ricardo; Bravo, Manuel A.; Lucena, Rafael; Toledo-Neira, Carla
    In this work, an analytical methodology was developed for determining polycyclic aromatic hydrocarbons (PAHs) in tea and coffee samples. The new analytical methodology uses a hydrophobic deep eutectic solvent (DES), consisting of a thymol and lidocaine mixture, for the extraction of the analytes under dispersive liquid-liquid microextraction. The extraction procedure was optimized considering several variables (extraction phase composition, sample volume, vortexing and centrifugation time). Under optimum conditions, an using ultrahigh-performance liquid chromatography with fluorescence detection as instrumental technique, the limits of detection were 39 and 53 ng & BULL;L-1 in tea and coffee samples, respectively. The precision expressed as relative standard deviation was better than 6.3 %.The relative recoveries were in the 60.7-85.2 % interval. The proposed method was successfully applied to the analysis of tea and coffee samples. The levels found for the six carcinogenic PAHs are between 10-45 & mu;g & BULL;L-1 for tea infusions and 6-31 & mu;g & BULL;L-1 for coffee infusions. The methodology is defined as an excellent green method with a score of 80 using the analytical Eco-scale.