A modified ionization difference UV–vis method for fast quantitation of guaiacyl-type phenolic hydroxyl groups in lignin

Chen, Lan; Wei, Xiaoxiao; Wang, Huan; Yao, Min; Zhang, Liming; Gellerstedt, Göran; Lindström, Mikeal E; Ek, Monica; Wang, Shuangfei; Min, Douyong

doi:10.1016/j.ijbiomac.2022.01.035

Cited by 10 publications

(21 citation statements)

References 38 publications

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“…46 However, the increasing tendency of Ph-OH contents after lignin phenola- tion could be well reflected by UV spectroscopy quantification, to a certain extent, which is a facile and fast method to reveal the degree of phenolation. In addition, considering the negative absorbance, we corrected the Ph-OH contents according to the modified ionization difference UV spectroscopy to give a range, 50 as shown in Tables S2 and S3. Phenol plays a dual role of reactant and solvent during lignin phenolation.…”

Section: ■ Introductionmentioning

confidence: 99%

Revealing the Structural Influence on Lignin Phenolation and Its Nanoparticle Fabrication with Tunable Sizes

et al. 2022

ACS Sustainable Chem. Eng.

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Phenolation is one of the most efficient ways to improve lignin's reactivity by increasing phenolic hydroxyl (Ph-OH) contents and active sites. However, due to its complex structural nature, the lignin structure significantly impacts the phenolation and its following nanoparticle fabrication. In this study, phenolation of cellulolytic enzyme lignin (CEL) and kraft lignin (KL) of Simao pine was conducted under appropriate acidcatalyzed conditions and the resultant phenolated lignins were comprehensively characterized. The main structural difference between KL and CEL arises from the content of β-aryl ether bonds, leading to varied increments of Ph-OH contents in phenolation. Size-controlled lignin nanoparticles (LNPs) were successfully prepared from phenolated lignins with lower molecular weight, lower aliphatic-OH content, and higher level of Ph-OH groups. The average diameters and surface charges of LNPs varied from 60 to 120 nm and −30 to −55 mV, respectively, which highly depended on the phenolation degree of lignin, especially the content of Ph-OH groups. It indicates that the structural features of phenolated lignin could facilitate LNP fabrication with tunable sizes. This study reveals the structural influences on lignin phenolation and its nanoparticle fabrication, providing new insights into the size-controlled design, preparation, and application of LNPs.

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Section: ■ Introductionmentioning

confidence: 99%

Revealing the Structural Influence on Lignin Phenolation and Its Nanoparticle Fabrication with Tunable Sizes

et al. 2022

ACS Sustainable Chem. Eng.

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“…Going back to the results in Figure , the methods by Lin & Dence as well as Gärtner et al did not surpass 2.4 mmol/g phenolic hydroxyl for either SKL1 or ASL1. , Both methods therefore provided an underestimation. In the case of the method by Chen et al, an overestimation is evident for SKL1 with all tested solvents but 2-methoxyethanol/water. It is interesting to note that this method yielded only 1.3 mmol/g with 2-methoxyethanol/water, since the method was originally calibrated with exactly this solvent and guaiacyl-type lignin, such as SKL1.…”

Section: Resultsmentioning

confidence: 95%

“…It has been indicated by other authors that a higher lignin absorptivity would be achieved with the better solvent. , To test this concept, the absorptivity of SKL1 and ASL1 at 280 nm was plotted against the HSP distance (Ra) from the sphere center, which was calculated from the difference of solvent and lignin HSP in eq . The underlying theory of the HSP model is that the lower the Ra value, i.e., the lower the distance from the sphere center, the better the solvent for dissolving the polymer.…”

Section: Resultsmentioning

confidence: 99%

“…This broad range of values attests a poor quality to the results, as in theory the values should agree. The phenolic hydroxyl according to Gärtner et al is in agreement with Lin & Dence, where Gärtner et al tended to yield on average higher values. , The results according to Chen et al were two to three times as much than the latter two. The overall trend, however, was the same when comparing different solvents.…”

Section: Resultsmentioning

confidence: 99%

“…By subtracting the neutral from the alkaline spectrum, the ionization difference spectrum is obtained . Different authors have correlated this difference spectrum with the abundance of phenolic hydroxyl groups in model compounds. ,, These methods can furthermore distinguish between structures such as conjugated, saturated, and α-carbonyl. Third, chemical modification of the lignin macromolecule can be probed by UV spectrophotometry.…”

Section: Introductionmentioning

confidence: 99%

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Ultraviolet Spectrophotometry of Lignin Revisited: Exploring Solvents with Low Harmfulness, Lignin Purity, Hansen Solubility Parameter, and Determination of Phenolic Hydroxyl Groups

Ruwoldt¹,

Opedal²,

Syverud³

2022

ACS Omega

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In this article, we explored solvents with lower harmfulness than established systems for UV spectrophotometry of lignin. By measuring the absorptivity in DMSO solvent at 280 nm, the purity of the lignin samples was addressed and compared with Klason and acid-soluble lignin. The general trend was an increasing absorptivity with increasing lignin purity; however, considerable scattering was observed around the sample mean. The Hansen solubility parameter (HSP) of four technical lignins was furthermore determined. The model was in line with the UV measurements, as solvents closer in HSP correlated with a higher absorptivity. Ethylene glycol was identified as a good solvent for lignin with low UV-cutoff. In addition, mixtures of propylene carbonate, water, and ethanol showed good suitability and a low cutoff of 215 nm. While DMSO itself was poorly suited for recording alkali spectra, blending DMSO with water showed great potential. Comparing three methods for determining phenolic hydroxyl units by UV spectrophotometry showed some discrepancies between different procedures and solvents. It appeared that the calibrations established with lignin model compounds may not be fully representative of the lignin macromolecule. More importantly, the ionization difference spectra were highly affected by the solvent of choice, even when using what are considered "good" solvents. At last, a statistical comparison was made to identify the most suitable solvent and method, and the solvent systems were critically discussed. We thus conclude that several solvents were identified, which are less harmful than established systems, and that the solubility of lignin in these is a crucial point to address when conducting UV spectrophotometry.

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Enzymatic hydrolysis of corn stover lignin by laccase, lignin peroxidase, and manganese peroxidase

Zhang

Dong

Song

et al. 2022

Bioresource Technology

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A modified ionization difference UV–vis method for fast quantitation of guaiacyl-type phenolic hydroxyl groups in lignin

Cited by 10 publications

References 38 publications

Revealing the Structural Influence on Lignin Phenolation and Its Nanoparticle Fabrication with Tunable Sizes

Revealing the Structural Influence on Lignin Phenolation and Its Nanoparticle Fabrication with Tunable Sizes

Ultraviolet Spectrophotometry of Lignin Revisited: Exploring Solvents with Low Harmfulness, Lignin Purity, Hansen Solubility Parameter, and Determination of Phenolic Hydroxyl Groups

Enzymatic hydrolysis of corn stover lignin by laccase, lignin peroxidase, and manganese peroxidase

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