DQFA-Artículos
URI permanente para esta colecciónhttps://hdl.handle.net/10953/276
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Examinando DQFA-Artículos por Autor "Ayora-Cañada, María José"
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Ítem Analytical pyrolysis (Py-GC-MS) for the assessment of olive mill pomace composting efficiency and the effects of compost thermal treatment(Elsevier, 2022) Peña-Rueda, Marta; Comino-Romero, Francisco; Aranda-Sanjuán, Víctor; Domínguez-Vidal, Ana; Ayora-Cañada, María JoséComposting is an interesting solution for recycling the large amount of residues typically generated in olive oil production areas, particularly olive mill pomace. Bulking agents must be added to wet olive mill pomace for composting. The diversity of the materials used (such as olive tree-pruning residues, animal manure, or straw) and the variable proportion, in which they are mixed, are responsible for the heterogeneity and variability of the quality of the produced compost. For this reason, a comprehensive characterization of compost organic matter is necessary to gain information about its stability and maturity useful as well as to predict its behavior as a soil amendment. In this work, fresh olive mill pomace and four composted olive mill pomace samples were characterized using analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC-MS). Results showed a large variety of pyrolysis products, many of which had a specific biochemical origin. Pyrolysis-GC-MS revealed a decrease in fatty acids and aliphatic compounds content with composting, along with carbohydrates degradation and an increase in phenolic and N-compounds levels. Furthermore, the differences observed in organic matter characteristics had an impact on agronomic aspects (water repellency and phytotoxicity). Thus, the occurrence of fatty acids in incompletely composted materials (mainly palmitic and cis-vaccenic acids) was associated with increased phytotoxicity and higher water repellency. The presence of chicken manure in the mixtures was proved to favor the humification process and the production of stabilized compost (characterized by a lower Aliphatic-C/Aromatic-C ratio and higher N-heterocycles content). Furthermore, in this work, the effectiveness of applying thermal treatments to improve compost quality has been evaluated. Analysis of the Py-GC-MS results by means of principal component analysis (PCA) revealed thermal rearrangement, predominantly aromatization, and loss of functional groups of carbohydrates, lignin, and proteins, at temperatures above 225 ºC. Interestingly, the results suggest that materials with a non-effective or incomplete composting process can be transformed by thermal treatment into more stable products, exhibiting similar agronomic characteristics as those have that undergone a more efficient biotransformation.Ítem Comparing mapping and direct hyperspectral imaging in stand-off Raman spectroscopy for remote material identification(Wiley, 2019) Gasser, Christoph; González-Cabrera, María; Ayora-Cañada, María José; Domínguez-Vidal, Ana; Lendl, BernhardStand-off Raman spectroscopy offers a highly selective technique to probe unknown substances from a safe distance. Often, it is necessary to scan large areas of interest. This can be done by pointwise imaging (PI), that is, spectra are sequentially acquired from an array of points over the region of interest (point-by-point mapping). Alternatively, in this paper a direct hyperspectral Raman imager is presented, where a defocused laser beam illuminates a wide area of the sample and the Raman scattered light is collected from the whole field of view (FOV) at once as a spectral snapshot filtered by a liquid crystal tunable filter to select a specific Raman shift. Both techniques are compared in terms of achievable FOV, spectral resolution, signal-to-noise performance, and time consumption during a measurement at stand-off distance of 15 m. The HSRI showed superior spectral resolution and signal-to-noise ratio, while more than doubling the FOV of the PI at laser power densities reduced by a factor of 277 at the target. Further, the output hyperspectral image data cube can be processed with state of the art chemometric algorithms like vertex component analysis in order to get a simple deterministic false color image showing the chemical composition of the target. This is shown for an artificial polymer sample, measured at a distance of 15 m.Ítem Monitoring organic matter transformation of olive oil production residues in a full-scale composting plant by fluorescence spectroscopy(Elsevier, 2024-08) Peña-Rueda, Marta; Domínguez-Vidal, Ana; Llorent-Martínez, Eulogio; Aranda-Sanjuán, Víctor; Ayora-Cañada, María JoséComposting wet olive mill pomace, the main by-product of two-phase centrifugation systems, is an attractive valorization strategy in the context of regenerative agriculture. A comprehensive study of the changes in fluorescence signatures during the co-composting of this residue with olive tree pruning wastes and animal manure in a full-scale composting plant was performed. This compost showed more complex features than others at the initial stages of the process, exhibiting a singular band in the synchronous spectrum (500 nm) here attributed to polyphenol-pectin interactions. PARAFAC-derived components from Excitation-Emission matrices (EEMs) of water extracts were compared with those of fractions isolated following alkaline extraction at different maturity stages. The increase with composting of the component associated with humic-like substances (Ex 225, 365 nm/Em 476 nm) was more marked in the isolated humic acid fraction than in water extracts. Thus, the predominance of fulvic-like substances in water extracts explains inconsistencies previously reported about the relevance of the humic-like component during the composting process and the extent of humification. Finally, the correlation between PARAFAC components and several compost maturity parameters was studied. The negative correlation between the protein-like component and the germination index was explained by the protein-polyphenol interactions reflected in the emission spectra of this component. A strong positive correlation between both fulvic and humic fluorescent components and cation exchange capacity was found. In general, mature compost showed C/N ≤ 20 and no phytotoxicity (GI around 60%) although differences related to the heterogeneity of the large composting pile were important.Ítem Monitoring UV-accelerated alteration processes of paintings by means of hyperspectral micro-FTIR imaging and chemometrics(Elsevier, 2021) González-Cabrera, María; Domínguez-Vidal, Ana; Ayora-Cañada, María JoséWe explored the potential of infrared hyperspectral microimages to investigate the alteration of organic binders in pictorial layers after artificial UV light ageing. A set of paint mockups was prepared considering three different binders, namely, rabbit glue (a collagen-based proteinaceous binder), linseed oil (representative of drying oils) and egg tempera (a mixture of egg yolk and linseed oil). Four pigments (vermilion, orpiment, azurite and lead white) were considered in order to investigate the influence of pigment-binder interaction, following color changes by means of fiber optic reflectance spectroscopy (FORS). FTIR micro-images provided a representative picture of the complex and heterogeneous structure of paintings since each pixel contained the whole spectrum of the sample area from it was recorded. Principal component analysis (PCA) was used to analyze the FTIR images data in order to extract useful information about spectral changes taking place during UV induced ageing. Significant trends were observed, mainly depending on the binders and their degradation as a consequence of UV exposition in this pilot study on model samples. Several processes, such as the oxidation of proteins with the formation of carbonyl moieties and changes in amide band positions have been detected in the case of rabbit skin glue. The evaporation of linseed oil, probably due to the breakdown of the triacylglycerols, has been noticed for the binder alone but not when it was mixed with the pigments. In these cases, other spectral features depending on the pigment have been observed in the loading plots upon oxidation, namely the broadening of the carbonyl band, the appearance of carboxylic and dicarboxylic acids and the formation of metal carboxylates. For egg tempera, the main changes detected were related to the oxidation of lipidic components present in egg yolk fraction. Furthermore, in this case, the trend observed in the score graphs suggested that the presence of lead white accelerates its oxidation. It is interesting to note the major stability of the colored pigments when using this binderÍtem Multisensor hyperspectral imaging approach for the microchemical analysis of ultramarine blue pigments(Nature portfolio, 2022) González‑Cabrera, María; Wieland, Karin; Eitenberger, Elisabeth; Bleier, Anna; Brunnbauer, Lukas; Limbeck, Andreas; Hutter, Herbert; Haisch, Christoph; Lendl, Bernhard; Domínguez-Vidal, Ana; Ayora-Cañada, María JoséThis work presents a multisensor hyperspectral approach for the characterization of ultramarine blue, a valuable historical pigment, at the microscopic scale combining the information of four analytical techniques at the elemental and molecular levels. The hyperspectral images collected were combined in a single hypercube, where the pixels of the various spectral components are aligned on top of each other. Selected spectral descriptors have been defined to reduce data dimensionality before applying unsupervised chemometric data analysis approaches. Lazurite, responsible for the blue color of the pigment, was detected as the major mineral phase present in synthetic and good quality pigments. Impurities like pyrite were detected in lower quality samples, although the clear identification of other mineral phases with silicate basis was more difficult. There is no correlation between the spatial distribution of the bands arising in the Raman spectra of natural samples in the region 1200–1850 cm−1 and any of the transition metals or rare earth elements (REE). With this information, the previous hypothesis (based on bulk analysis) attributing these bands to luminescence emissions due to impurities of these elements must be revised. We propose the consideration of CO2 molecules trapped in the cages of the aluminosilicate structure of sodalite-type. Additionally, correlation between certain Raman features and the combined presence of Ca, P, and REE, in particular Nd, was detected for the lowest quality pigment. Our results highlight the usefulness of fusing chemical images obtained via different imaging techniques to obtain relevant information on chemical structure and properties.Ítem Natural or synthetic? Simultaneous Raman/luminescence hyperspectral microimaging for the fast distinction of ultramarine pigments(Elsevier, 2020) González-Cabrera, María; Arjonilla, Paz; Domínguez-Vidal, Ana; Ayora-Cañada, María JoséGenuine ultramarine has been one of the most precious blue pigments employed since ancient times. It used to be obtained by crushing and grinding the lapis lazuli rock and selectively extracting the blue mineral lazurite. Since 1828, when it was produced the synthetic version, the use of this much less expensive material became widespread and synthetic ultramarine blue replaced the natural one in painting palettes. The distinction between natural and synthetic ultramarine is, therefore, an important goal in authentication issues. Here, we present a hyperspectral microRaman imaging analysis, complemented with the characterization of ultramarine pigment samples in terms of colour, elemental composition and identification of crystalline phases by means of fiber optics reflection spectroscopy (FORS), X-Ray Fluorescence (XRF) and X-Ray diffraction (XRD), respectively. We show that a characteristic luminescence signature, easily detected in the course of standard Raman spectroscopic analysis using 785 nm as excitation, is indicative of the natural origin of the ultramarine blue pigments. Furthermore, simultaneous Raman/luminescence hyperspectral microimages allow the distinction between natural pigments of different quality thanks to the different intensity and spatial distribution of the lazurite characteristic band at 548 cm 1 and those of the luminescent impurities in the region between 1200 and 2000 cm 1. The establishment of a range of quality between different samples of lapis lazuli was also attempted taking into account the variations in the intensity of the Raman bands located at 548 cm 1 and 1286 cm 1. Finally, the feasibility of using the simultaneous Raman/luminescence features for authentication of ultramarine blue in a real historical context, even with non-invasive investigations, is illustrated with examples of different types of blue decorations from several halls of the Alhambra monumental ensemble, in Granada.Ítem Raman and Fourier transform infrared microspectroscopies reveal medieval Hispano–Muslim wood painting techniques and provide new insights into red lead production technology(Wiley, 2019) Arjonilla, Paz; Domínguez-Vidal, Ana; Correa, Elena; Domene-Ruiz, María José; Ayora-Cañada, María JoséThis paper describes the study of two Nasrid polychrome wooden ceilings from the Alhambra monumental ensemble using vibrational spectroscopic techniques. The study is focused on the identification of the constituent materials and execution techniques used employing non‐invasive and non‐destructive scientific investigation methods. Information about both inorganic (pigments) and organic (binders and coatings) materials has been obtained without the need for time‐consuming procedures. A complex stratigraphy involving the use of a protective priming layer of red lead covered with animal glue and white lead was revealed. The identification of Raman signatures of different lead oxide compounds, including lead‐tin oxide (Pb2SnO4), in the priming layer, allowed us to hypothesize the synthesis of red lead (Pb3O4) from litharge (α‐PbO), a common by‐product of the cupellation process used since antiquity for silver production. Furthermore, the pigments employed in hidden drawings found in the reverse of the wood pieces of one of the ceilings were also studied and compared with those found in the visible external face.Ítem Romantic restorations in the Alhambra monument: Spectroscopic characterization of decorative plasterwork in the Royal Baths of Comares(Wiley, 2019) Arjonilla, Paz; Ayora-Cañada, María José; Rubio-Domene, Ramón; Correa, Elena; de-la-Torre-López, María José; Domínguez-Vidal, AnaThe polychrome plasterwork decorations of the Room of the Beds in the RoyalBath of Comares of the Alhambra monumental ensemble have been studiedusing Raman microspectroscopy and complementary techniques. This areakeeps the testimony of the controversial restorations carried out in the 19thcentury in an attempt to imitate the lost original appearance of the authenticNasrid plasterwork. Raman spectroscopy and energy dispersive X‐ray fluores-cence have been employed to identify the pigments and extenders. Scanningelectron microscopy–energy dispersive X‐ray spectroscopy has been used togain additional information about the morphology of the painting layers. Addi-tionally, infrared microspectroscopy provided insight into the nature of theorganic materials employed as binders. Vermillion, synthetic ultramarine blue,hematite, and carbon black were clearly identified in red, blue, brown, andblack decorations by Raman spectroscopy. Green decorations were executedwith a copper‐arsenic pigment that could not be unambiguously identifiedalthough the presence of Raman bands typical of arsenate stretching bandscould point to alteration processes of copper arsenite pigments. Regardingthe execution technique, the pictorial layer was applied over a preparationlayer of white lead that also contained barite using a proteinaceous binder.The presence of anglesite and other phases related to hydrocerussite alterationdue to humidity and salts was also evidenced. Finally, a comparison of thematerials found in this redecoration with those identified in original Nasriddecorations has been performed, revealing noticeable differences in both thematerials and the execution technologiesÍtem Understanding the compositional changes of organic matter in torrefied olive mill pomace compost using infrared spectroscopy and chemometrics(Elsevier, 2023) Peña-Rueda, Marta; Comino-Romero, Francisco; Aranda-Sanjuán, Víctor; Ayora-Cañada, María José; Domínguez-Vidal, AnaComposting olive mill pomace (OMP), the major by-product of the olive oil industry, is an attractive waste management practice in the context of sustainable food production. Thermal treatment of compost at mild temperatures (torrefaction) can aid to improve its characteristics as a soil amendment. This study aims to understand the chemical changes occurring during torrefaction of olive mill pomace-based (OMP) compost, as well as to evaluate the treatment effects on compost at different stages of maturation. Here, treatments at different temperatures (175, 225, and 275 °C) and duration (from 1 to 5 h) have been employed to obtain a sort of torrefied samples. In general, the H/C and O/C atomic ratios of compost samples decreased with torrefaction temperatures, which suggests an incipient coalification of the organic matter. Furthermore, the results showed that a combination of FT-NIR and FT-MIR spectroscopy using a low-level data fusion strategy is very sensitive to the molecular changes occurring both in the composting process and during heating. Principal Component Analysis (PCA) of the merged spectra revealed that the changes at 175 °C are mainly the loss of water (O–H contributions at 3300 and 5169 cm−1) together with the degradation of proteins (observed in the decrease of amide I and II characteristic bands). Furthermore, the samples heated at this temperature can still be differentiated by their initial maturation stage. On the other hand, thermochemical changes occurring at higher temperatures are more intense and make the samples more alike, independently of the composting time. When heating above 225 °C, the loss of O–H happens together with the decrease of aliphatic moieties, reflected in the bands 2920 and 2850 cm−1 (FT-MIR) and 4258, 4323, 5665, and 5781 cm−1 (FT-MIR). This can be attributed to the thermal degradation of cellulosic materials and, additionally, to the degradation of the residual oil in the case of poorly composted samples. Heated samples are characterized by the presence of carbonyl groups (1709 cm−1) and humic-like complex and polymerized aromatic structures (1579 cm−1). Since the characteristics of the torrefied compost at 275 °C are very similar regardless of the initial maturation stage, torrefaction may be a very interesting way to reduce the composting time of olive mill pomace to obtain a high-quality organic amendment for soil application.