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Galetta M.A.,University of the Republic of Uruguay | Reina L.,University of the Republic of Uruguay | Resquin F.,Instituto Nacional Of Investigacion Agropecuaria Tacuarembo | Mantero C.,University of the Republic of Uruguay | And 4 more authors.
Journal of Analytical and Applied Pyrolysis | Year: 2014

Analytical pyrolysis (Py-GC/MS) at 500 °C was applied to study wood composition of Eucalyptus species (Eucalyptus grandis, Eucalyptus dunnii and Eucalyptus benthamii) which are relevant for pulping in Uruguay. Multivariate data treatments mainly principal component analysis and discriminant analysis were used to explore differences between the original wood cultivars. Multivariate analyses with automatic backwards variable selection indicated that simplified methoxyphenol patterns (up to 10 compounds) are sufficient for wood discrimination in terms of species and geographical origin but also with purposes of forecasting the ease of delignification of the resulting pulps measured as active alkali. No additional chemotaxonomical accuracy was achieved when the data sets were enlarged with carbohydrate-derived products. On the other side, discriminant or forecasting models (partial least squares and multiple linear regression) were much less significant when based on individual diagnostic compounds, groups of compounds, or the classical syringyl-to-guaiacyl (S/G) ratio. Principal component analysis indicated that the variability in lignin composition due to bioclimatic variations (spatial replications) was more significant than that due to phylogenetic differences (species and cultivars). © 2014 Elsevier B.V. All rights reserved.

Gonzalez-Perez J.A.,IRNAS CSIC | Jimenez-Morillo N.T.,IRNAS CSIC | de la Rosa J.M.,IRNAS CSIC | Almendros G.,MNCN CSIC | Gonzalez-Vila F.J.,IRNAS CSIC
Journal of the Science of Food and Agriculture | Year: 2016

BACKGROUND: Pyrolysis-compound specific isotopic analysis (Py-CSIA: Py-GC-(FID)-C-IRMS) is a relatively novel technique that allows on-line quantification of stable isotope proportions in chromatographically separated products released by pyrolysis. Validation of the Py-CSIA technique is compulsory for molecular traceability in basic and applied research. In this work, commercial sucrose from C4 (sugarcane) and C3 (sugarbeet) photosystem plants and admixtures were studied using analytical pyrolysis (Py-GC/MS), bulk δ13C IRMS and δ13C Py-CSIA. RESULTS: Major pyrolysis compounds were furfural (F), furfural-5-hydroxymethyl (HMF) and levoglucosan (LV). Bulk and main pyrolysis compound δ13C (‰) values were dependent on plant origin: C3 (F, -24.65 ± 0.89; HMF, -22.07 ± 0.41‰ LV, -21.74 ± 0.17‰) and C4 (F, -14.35 ± 0.89‰ HMF, -11.22 ± 0.54‰ LV, -11.44 ± 1.26‰). Significant regressions were obtained for δ13C of bulk and pyrolysis compounds in C3 and C4 admixtures. Furfural (F) was found 13C depleted with respect to bulk and HMF and LV, indicating the incorporation of the light carbon atom in position 6 of carbohydrates in the furan ring after pyrolysis. CONCLUSION: This is the first detailed report on the δ13C signature of major pyrolytically generated carbohydrate-derived molecules. The information provided by Py-CSIA is valuable for identifying source marker compounds of use in food science/fraud detection or in environmental research. © 2015 Society of Chemical Industry © 2016 Society of Chemical Industry.

Gonzalez-Perez J.A.,IRNAS CSIC | Jimenez-Morillo N.T.,IRNAS CSIC | de la Rosa J.M.,IRNAS CSIC | Almendros G.,MNCN CSIC | Gonzalez-Vila F.J.,IRNAS CSIC
Journal of Chromatography A | Year: 2015

Polyethylene is probably the most used plastic material in daily life and its accurate analysis is of importance. In this communication the chemical structure of polyethylenes is studied in detail using conventional analytical pyrolysis (Py-GC/MS), bulk stable isotopic analysis (IRMS) and pyrolysis compound specific stable isotopic analysis (Py-CSIA) to measure stable isotope proportions (δ13C, δ15N and δD) of polyethylene pyrolysis compounds. Polyethylene pyrolysis yields triplet peaks of n-alkanes, α-alkenes and α,ω-alkanedienes. No differences were found for bulk δ13C among different polyethylene types. However, conspicuous differences in δD were evident. It was possible to assign structure δ13C and δD values to specific polyethylene pyrolysis products in the range 12-18 carbon chain length. Conspicuous differences were found for the pyrolysis products with unsaturated moieties showing significant higher δD values than saturated chains (alkanes) that were deuterium depleted. In addition, a full isotopic fingerprinting (δ13C, δ15N and δD) for a dye (o-chloroaniline) contained in a polyethylene is reported. To the best of our knowledge this is the first application Py-CSIA to the study of a synthetic polymer. This hyphenated analytical technique is a promising tool to study synthetic materials, providing not only a fingerprinting, but also allowing the traceability of the polymerization process and the origin of the materials. © 2015 Elsevier B.V.

Gonzalez-Perez J.A.,IRNAS CSIC | Almendros G.,MNCN CSIC | De La Rosa J.M.,IRNAS CSIC | Gonzalez-Vila F.J.,IRNAS CSIC
Journal of Analytical and Applied Pyrolysis | Year: 2014

Large number of studies has demonstrated the usefulness of flash pyrolysis in association with GC-MS in releasing diagnostic volatile compounds informing about the complex composition of natural organic matter (NOM). This knowledge is of interest as regards monitoring agricultural and environmental processes including pollution. In this context the term NOM comprises a wide array of biomacromolecules (lignins, polysaccharides, proteins, lipid polymers, etc.), as well as complex three-dimensional macromolecules, either labile or recalcitrant, and which are referred to with generic terms such as dissolved organic matter, humic substances and black carbon. In this communication an updated overview on recent advances achieved by analytical pyrolysis in the structural characterization of recalcitrant/fossil/NOM is presented, with particular focus in the detection of polycyclic aromatic compounds (PAHs) within complex organic matrices. © 2014 Elsevier B.V.

Tinoco P.,Alfonso X El Sabio University | Almendros G.,MNCN CSIC | Gonzalez-Vila F.J.,IRNAS CSIC | Sanz J.,IQOG CSIC | Gonzalez-Perez J.A.,IRNAS CSIC
Journal of Soils and Sediments | Year: 2015

Purpose: Aromaticity of soil organic matter has often been considered an independent index of biogeochemical maturity, recalcitrance, and persistence of C in soils. The structural characteristics of soil humic acids (HAs) from various origins are studied by bi- and multivariate statistical exploratory analyses to select chemical descriptors surrogated to aromaticity. Materials and methods: Structural features of 16 HAs were determined using analytical pyrolysis, wet chemical oxidation, and a variety of spectroscopic analyses. Data management was approached by (a) linear correlations between classical HAs structural descriptors and the concentration of aromatic C as seen by 13C NMR spectra as independent variable and (b) multivariate statistics to define HA aromaticity as an emergent property defined by the shared contribution of a set of variables. Results and discussion: Significant correlations were found between HAs optical density (465 nm; E4) and aromatic C regions (13C NMR). These also paralleled the intensity of the Fourier Transform Infrared Spectroscopy (FT-IR) bands ascribed to aromatic structures. Likewise, significant positive correlations were observed between E4 and aromatic compounds released by wet chemical degradation, with negative correlations with yields of aliphatic and lignin-derived methoxyphenols released by pyrolysis. Conclusions: Multivariate classification of HAs’ analytical descriptors allows the identification of variables, i.e., E4, H/C atomic ratio, intensity of aromatic C in the 13C NMR region between 110–140 and 140–160 ppm, and yield of benezenecarboxylic acids after chemical degradation, as surrogates for HAs’ aromaticity. This HA characteristic is also responsive to the variability between environmental scenarios, mainly the effect of wildfires and soil management (clearing and cultivation). © 2014, Springer-Verlag Berlin Heidelberg.

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