scholarly journals An easy and reliable method for syringyl: guaiacyl ratio measurement

TAPPI Journal ◽  
2017 ◽  
Vol 16 (03) ◽  
pp. 145-152
Author(s):  
Raquel Prado ◽  
Lisa Weigand ◽  
Shikh M.S.N.S. Zahari ◽  
Xabier Erdocia ◽  
Jason Hallett ◽  
...  
Keyword(s):  
Quantum Coherence ◽  
Partial Least Squares Regression ◽  
Attenuated Total Reflection ◽  
Gas Chromatography Mass Spectrometry ◽  
Least Squares Regression ◽  
Pyrolysis Gas ◽  
Simple Method ◽  
Ratio Measurement ◽  
Complex Process ◽  
G Ratio

Lignin structure elucidation is one of the main targets for biorefinery related research. Because of its complexity, obtaining reproducible results in a straight-forward way is very important. One of the values that is used to compare different lignins is the syringyl:guaiacyl (S/G) ratio, which has been measured in different ways. The most reliable result is obtained for nitrobenzene oxidation, but this involves a complex process. In this work, the S/G ratios measured by pyrolysis-gas chromatography mass spectrometry (py-GCMS) and heteronuclear single quantum coherence-nuclear magnetic resonance (HSQC-NMR) spectroscopy were compared with attenuated total reflection infrared (ATR-IR) spectroscopy results to establish a reliable, quick, and simple method for the measurement. To achieve this, two mathematical models were applied with multivariate data analysis software. A partial least squares regression model for py-GCMS gave the best result.

scholarly journals Predictive modelling of the water contact angle of surfaces using attenuated total reflection – Fourier transform infrared (ATR-FTIR) chemical imaging and partial least squares regression (PLSR)

The Analyst ◽  
2018 ◽  
Vol 143 (15) ◽  
pp. 3729-3740 ◽  
Author(s):  
S. Mukherjee ◽  
J. Á. Martínez-González ◽  
D. P. Dowling ◽  
A. A. Gowen
Keyword(s):  
Contact Angle ◽  
Fourier Transform ◽  
Partial Least Squares Regression ◽  
Predictive Modelling ◽  
Chemical Imaging ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Least Squares Regression ◽  
Water Contact ◽  
Simple Method

A simple method to model and predict the surface wettability using a combination of ATR-FTIR imaging and PLSR modelling.

scholarly journals Are agricultural plastic covers a source of plastic debris in soil? A first screening study

2021 ◽  
Author(s):  
Zacharias Steinmetz ◽  
Paul Löffler ◽  
Silvia Eichhöfer ◽  
Jan David ◽  
Katherine Muñoz ◽  
...  
Keyword(s):  
Attenuated Total Reflection ◽  
Gas Chromatography Mass Spectrometry ◽  
Short Term ◽  
Pyrolysis Gas ◽  
Wind Drift ◽  
Plastic Debris ◽  
Fine Soil ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Screening Study ◽  
External Sources

Abstract. Agricultural plastic covers made from polyethylene (PE) and polypropylene (PP) offer increased yields and an improved crop quality. However, such covers are suspected of partially breaking down into smaller debris and thereby contributing to soil pollution with microplastics. To scrutinize this, we randomly sampled 240 topsoil cores (0–5 cm) from eight fields covered with fleeces, perforated foils, and plastic mulches for less than two years. Samples from the field periphery (50 m perimeter) served as reference. Visual plastic debris > 2 mm was analyzed by Fourier transformed infrared spectroscopy with attenuated total reflection (FTIR–ATR). Smaller, soil-associated plastic debris was dispersed from 50 g of fine soil (≤ 2 mm) using sodium hexametaphosphate solution and density-separated with saturated NaCl solution. The collected PE, PP, and polystyrene (PS) debris was selectively dissolved in a mixture of 1,2,4-trichlorobenzene and p-xylene at 150 °C and quantified by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). We counted six PE and PS fragments > 2 mm in two out of eight fields. By contrast, Py-GC/MS analysis revealed PE, PP, and PS contents > 1 µg g−1 in seven fields (17 % of all samples). In three fields, PE levels of 3–35 µg g−1 were associated with the use of thinner and less durable perforated foils (40 µm thickness). This was slightly more pronounced at field edges where the plastic covers are turned and weighted down. By contrast, 50 µm thick PE films were not indicated to emit any plastic debris. PP contents of 5–10 µg g−1 were restricted to single observations in the field centers of three sites. On one site, we found expanded PS particles >2 mm that concurred with elevated PS levels (8–19 µg g−1) in the fine soil. Both PP and PS were distributed indistinctly across sites so that their source remained unresolved. In addition, the extent to which plastic contents of up to 7 µg g−1 in the field periphery of some sites were attributed to wind drift from the covered fields or from external sources needs to be investigated in future studies. Yet, our results suggest that the short-term use of thicker and more durable plastic covers should be preferred to limit plastic emissions and accumulation in soil.

scholarly journals New Insights on Structures Forming the Lignin-Like Fractions of Ancestral Plants

2021 ◽  
Vol 12 ◽  
Author(s):  
Jorge Rencoret ◽  
Ana Gutiérrez ◽  
Gisela Marques ◽  
José C. del Río ◽  
Yuki Tobimatsu ◽  
...  
Keyword(s):  
Structural Information ◽  
2D Nmr ◽  
Plant Evolution ◽  
Pteridium Aquilinum ◽  
Gas Chromatography Mass Spectrometry ◽  
Aryl Ether ◽  
Pyrolysis Gas ◽  
Alkyl Aryl ◽  
Two Samples ◽  
G Ratio

In the present work, lignin-like fractions were isolated from several ancestral plants –including moss (Hypnum cupressiforme and Polytrichum commune), lycophyte (Selaginella kraussiana), horsetail (Equisetum palustre), fern (Nephrolepis cordifolia and Pteridium aquilinum), cycad (Cycas revoluta), and gnetophyte (Ephedra fragilis) species– and structurally characterized by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy. Py-GC/MS yielded marker compounds characteristic of lignin units, except in the H. cupressiforme, P. commune and E. palustre “lignins,” where they were practically absent. Additional structural information on the other five samples was obtained from 2D-NMR experiments displaying intense correlations signals of guaiacyl (G) units in the fern and cycad lignins, along with smaller amounts of p-hydroxyphenyl (H) units. Interestingly, the lignins from the lycophyte S. kraussiana and the gnetophyte E. fragilis were not only composed of G- and H-lignin units but they also incorporated significant amounts of the syringyl (S) units characteristic of angiosperms, which appeared much later in plant evolution, most probably due to convergent evolution. The latter finding is also supported by the abundance of syringol derivatives after the Py-GC/MS analyses of these two samples. Regarding lignin structure, β−O−4′ alkyl-aryl ethers were the most abundant substructures, followed by condensed β−5′ phenylcoumarans and β−β′ resinols (and dibenzodioxocins in the fern and cycad lignins). The highest percentages of alkyl-aryl ether structures correlated with the higher S/G ratio in the S. Kraussiana and E. fragilis lignin-like fractions. More interestingly, apart from the typical monolignol-derived lignin units (H, G and S), other structures, assigned to flavonoid compounds never reported before in natural lignins (such as amentoflavone, apigenin, hypnogenol B, kaempferol, and naringenin), could also be identified in the HSQC spectra of all the lignin-like fractions analyzed. With this purpose, in vitro synthesized coniferyl-naringenin and coniferyl-apigenin dehydrogenation polymers were used as standards. These flavonoids were abundant in H. cupressiforme appearing as the only constituents of the moss lignin-like fraction (including 84% of dimeric hypnogenol B) and their abundance decreased in those of S. Kraussiana (with amentoflavone and naringenin representing 14% of the total aromatic units), and the two ancient gymnosperms (0.4–1.2%) and ferns (0–0.7%).

scholarly journals Material Analysis and a Visual Guide of Degradation Phenomena in Historical Synthetic Polymers as Tools to Follow Ageing Processes in Industrial Heritage Collections

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 121
Author(s):  
Till Krieg ◽  
Cristian Mazzon ◽  
Elena Gómez-Sánchez
Keyword(s):  
Synthetic Polymers ◽  
Attenuated Total Reflection ◽  
Gas Chromatography Mass Spectrometry ◽  
Pyrolysis Gas ◽  
Industrial Heritage ◽  
Visual Damage ◽  
Material Information ◽  
Underlying Processes ◽  
Heritage Collections

Identifying the most vulnerable plastics and monitoring their deterioration is one of the main problems within heritage collections with historical synthetic polymers. Gathering and interpreting data about material and degradation phenomena in a collection reveals its conservation needs. A systematic survey of the collection can help towards this purpose. Surveys aiming at inspecting and documenting damages rely on several tools in order to fulfill their purpose. Firstly, objective descriptions of the damages that may appear, and secondly, the means of acquiring and interpreting material information. To address these needs, this article presents (a) a visual damage catalogue of degradation phenomena in plastic and rubber materials, and (b) the implementation of Fourier-transform infrared spectroscopy (FTIR) and pyrolysis–gas chromatography–mass spectrometry (py-GCMS) for the identification of analytically challenging rubber materials and of blooming phenomena. The damage catalogue is based solely on visual and olfactory signs, so that the assessment is independent of possible causes of damages and underlying processes, with the purpose of allowing objectivity to prime over interpretation. The limitations of the use of FTIR in the identification of heavily compounded rubbers in museum surveys is highlighted, and examples are presented. The use of py-GCMS on these cases conveniently allowed the identification of the constituting monomers of several rubber materials where FTIR could not provide a univocal classification of the material present. The study of several cases of blooming allowed the identification of diverse compositions and origins, showing that the description of a degradation phenomenon is only the first step towards its understanding. Unveiling the nature of a particular case of blooming is particularly critical when conservation treatments, such as the removal of a (potentially protecting) layer, are planned. For this purpose, attenuated total reflection-FTIR (ATR-FTIR) as a surface technique was particularly useful.

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