Analysis of the substituent distribution along the chain of water-soluble methyl cellulose by combination of enzymatic and chemical methods

Saake, Bodo; Lebioda, Sascha; Puls, Jürgen

doi:10.1515/hf.2004.013

Cited by 19 publications

(27 citation statements)

References 24 publications

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“…In the forthcoming second part of the study, we will show how solid-state NMR can be used for the determination of the DS values of solid methylated celluloses. These results will be compared with data from alternative (wet-chemical or spectroscopic) analyses (Saake et al 2004). …”

Section: Introductionmentioning

confidence: 99%

Solid-state NMR studies of methyl celluloses. Part 1: regioselectively substituted celluloses as standards for establishing an NMR data basis

et al. 2008

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Three methyl celluloses with completely uniform substitution pattern, 2-O-methyl cellulose (1), 3-O-methyl cellulose (2) and 6-O-methyl cellulose (3), were prepared according to the cationic ring opening polymerization approaches starting from substituted 1,2,4-orthopivalate derivatives of D-glucose. These samples allowed for the first time to sort out the methyl substitution effects on solid-state NMR chemical shifts and relaxation. Dipolar dephasing experiments allowed the detection and assignment ( 1 H, 13 C) of the methyl groups. In 1 and 2, these resonances overlapped with those of C-6, whereas in 3, the methyl signal experienced a low-field shift into the region of C-2,3,5. 13 C T 1 experiments were used to verify different relaxation behavior of the carbon sites, particularly the short relaxation time of at the carbon substitution site next to the methyl groups. This effect was used to unambiguously identify the 13 C chemical shifts of the carbons carrying the methoxyl substituent, although they overlap with all resonances in the C-2,3,5 region. The data obtained for the standard samples with uniform substitution will now be used as the basis for determining methylation patterns and substitution degree in commercial methyl celluloses.

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Section: Introductionmentioning

confidence: 99%

Solid-state NMR studies of methyl celluloses. Part 1: regioselectively substituted celluloses as standards for establishing an NMR data basis

et al. 2008

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“…The overall DS values of the four samples (named as H142-H145) were 1.96, 1.53, 1.05 and 0.51, respectively (Saake et al 2004). …”

Section: Wet Chemical Analysismentioning

confidence: 98%

“…The degree of substitution and the distribution of methyl substituents between the substitution sites were determined according to the previously published protocols (Saake et al 2004). In short, standard compounds of glucopyranosides with different methyl substitution patterns were produced by acid hydrolysis of a methyl cellulose sample and chromatographic separation of the constituents (one trisubstituted, three disubstituted, three monosubstituted and one nonsubstituted glucopyranose).…”

Section: Wet Chemical Analysismentioning

confidence: 99%

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Solid-state NMR studies of methyl celluloses. Part 2: Determination of degree of substitution and O-6 vs. O-2/O-3 substituent distribution in commercial methyl cellulose samples

Karrasch

Jäger

Saake³

et al. 2009

Cellulose

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Solid state NMR spectroscopy was applied to determine the overall degree of substitution (DS) and the degrees of substitution at C-6 (DS C-6 ) and C-2/3 (DS C-2/3 ). Four commercial methyl cellulose samples were used, having a DS between 0.51 and 1.96 as determined by wet-chemical analysis. The strategy and optimization of the NMR data acquisition as well as the data evaluation procedures are explained in detail. Optimization of the approach mainly comprised (a) maximizing the signal by choice of NMR probe, MAS spinning frequency and B 0 field, (b) minimizing the measurement time by a Torchia-type experiment and (c) suppressing probe background by rotor-synchronized echo detection. Data evaluation used simply the integration of three different spectral ranges in the 13 C NMR spectrum. The results of the experiments were in good agreement with the wet-chemical data. The NMR approach takes about the same analysis time as the conventional hydrolysis/chromatography analysis. However, it is a generally applicable and simple alternative without need for an extended sample preparation which is most useful if wet-chemical/ chromatographic analyses are undesired or unavailable. Further studies have to concentrate on the validation of the analytical method and application to a larger sample array.

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“…Lately, enzymes have especially been used by the groups of Gorton and Tjerneld [4][5][6][7] and of Puls and Saake [8][9][10][11] in cellulose ether analysis. Degraded samples have been investigated by SEC-MALLS/RI and fractions obtained have been studied with respect to their monomer composition.…”

Section: Introductionmentioning

confidence: 99%

The Applicability of Enzymes in Cellulose Ether Analysis

Adden

Melander

Brinkmalm

et al. 2009

Macromolecular Symposia

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Summary: Six methyl cellulose (MC) samples, one with a DS of 1.32 and five with a DS between 1.83 and 1.88, were degraded with five different enzymes or enzyme preparations containing endoglucanases. The main goal was to investigate whether enzymes could be used for determination of heterogeneity of the substituent distribution along the cellulose chain. To obtain information about the heterogeneity it was necessary to gather information on how the enzymes affect hydrolysis. Monomer composition and methyl distribution in the polymer chain were analyzed after total or partial random hydrolysis and appropriate derivatization by GC and MS, respectively, and used as reference data for the evaluation of the enzymatic hydrolysis. Size exclusion chromatography with multi angle light scattering and refractive index detection (SEC-MALLS/RI) was used to estimate molar mass distribution of the MCs before and after hydrolysis. Electrospray and matrix assisted laser desorption/ionization (ESI and MALDI) in combination with various MS analyzers were compared with respect to quantification of the degradation products directly and after perdeuteromethylation. Methyl group distribution in the oligomeric fractions and the average DS/DP were calculated from ESI mass spectra. With help of the reference analysis, patterns could be corrected for the unspecific contribution of end groups. By labelling and ESI-MS n , our knowledge about the tolerance of the enzyme's sub-sites with respect to the number of methyl groups could be improved. A novel standard addition method in combination with electrospray ionization ion trap mass spectrometry (ESI-IT MS) was used to determine the amount of formed oligomers.

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Analysis of the substituent distribution along the chain of water-soluble methyl cellulose by combination of enzymatic and chemical methods

Cited by 19 publications

References 24 publications

Solid-state NMR studies of methyl celluloses. Part 1: regioselectively substituted celluloses as standards for establishing an NMR data basis

Solid-state NMR studies of methyl celluloses. Part 1: regioselectively substituted celluloses as standards for establishing an NMR data basis

Solid-state NMR studies of methyl celluloses. Part 2: Determination of degree of substitution and O-6 vs. O-2/O-3 substituent distribution in commercial methyl cellulose samples

The Applicability of Enzymes in Cellulose Ether Analysis

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