| 1. |
- Alipour, Nazanin, et al.
(författare)
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Release of micro- and nanoparticles from a polypropylene/clay nanocomposite, a methodology for controlled degradation and evaluation
- 2021
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 319
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Tidskriftsartikel (refereegranskat)abstract
- A methodology was developed for qualitative assessment and characterisation of particle losses from nanocomposites during service life. The methodology can be generalised to other systems where the material fragments during ageing and can be extended to quantitative analysis. A chamber was constructed for ageing of selected materials, which enabled effective collection and subsequent analysis of released particles. A combination of scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy was found to be suitable for characterising particles in terms of size, shape and content. The methodology was tested on a common nanoclay composite with polypropylene as the matrix. There was no need for physical/mechanical wear to generate particles, slow flow of air and elevated temperature led to cracking and fragmentation of the material, and subsequent release of nanocomposite particles containing embedded or protruding clay. The release of pure clay particles and polypropylene particles was also detected. Using the methodology, it was observed that even in ‘mild’ degradation conditions (pure thermo-oxidation with no wear), fillers and nanocomposite particles can be released to the environment, which is an environmental and health concern. © 2021 The Authors
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| 2. |
- Enebro, Jonas, 1979-, et al.
(författare)
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A New Approach for Studying Correlations between the Chemical Structure and the Rheological Properties in Carboxymethyl Cellulose
- 2007
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 8:10, s. 3253-3257
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Tidskriftsartikel (refereegranskat)abstract
- Two model sodium carboxymethyl celluloses (CMC) with similar monomer composition but with significant differences in the viscoelastic properties, that could not be assigned to variations in the average molar mass or molar mass distribution, were investigated with respect to the fraction of nonsubstituted cellulose segments in the polymers. The CMCs were hydrolyzed by a purified highly selective endoglucanase. The average molar mass and molar mass distribution of the enzyme products, as measured by size-exclusion chromatography with online multi-angle light scattering and refractive index detection (SEC/MALS/RI), revealed that the enzyme-catalyzed hydrolysis was more effective on one of the CMCs. To investigate whether this was due to a higher fraction of nonsubstituted cellulose segments in the polymer, the concentrations of nonsubstituted enzyme products, e.g., cellotetraose and cellopentaose, were measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). It was concluded that the two CMCs displayed significant differences in the fraction of nonsubstituted cellulose segments. Furthermore, the CMC with the strongest attractive intermolecular interactions, according to rheometry, also contained the highest fraction of nonsubstituted cellulose segments.
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| 3. |
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| 4. |
- Enebro, Jonas, et al.
(författare)
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Improved matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of carboxymethyl cellulose
- 2006
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 20:24, s. 3693-3698
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Tidskriftsartikel (refereegranskat)abstract
- A refined sample preparation procedure for matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) was developed for the evaluation of the degree of substitution (DS) in partially depolymerised carboxymethyl cellulose (CMC). By adding ammonium sulphate to the sample mixture prior to the analysis, good quality mass spectra could be acquired. The usual time-consuming search for 'sweet-spots' at the crystalline rim of the MALDI target spot was also avoided. This quality improvement made it possible to investigate whether various positions on the target spot generated mass spectra in which the measured DS varied. The accuracy and reproducibility of the sample preparation procedure were tested by applying it on three commercial CMCs. The study shows that the DS values that were calculated from the spectra acquired from the centre region of the MALDI target spot were in better agreement with the DS provided by the supplier than were the values obtained from the large crystals at the target spot rim. This observation could be one reasonable explanation for the higher DS values reported in other publications. By applying our refined MALDI sample preparation procedure DS values that were in good agreement with the values provided by the manufacturer could be obtained. This indicates that MALDI-TOFMS of partially depolyrnerised CMCs can be used for an estimation of the DS as a complement to the more established methods, e.g. NMR, titrimetry, and chromatographic techniques.
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| 5. |
- Enebro, Jonas, 1979-, et al.
(författare)
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Investigation of endoglucanase selectivity on carboxymethyl cellulose by mass spectrometric techniques
- 2009
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 16:2, s. 271-280
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Tidskriftsartikel (refereegranskat)abstract
- The benefits of applying cellulose selective enzymes as analytical tools for chemical structure characterization of cellulose derivatives have been frequently addressed over the years. In a recent study the high selectivity of cellulase Cel45A from Trichoderma reesei (Tr Cel45A) was utilized for relating the chemical structure to the flow properties of carboxymethyl cellulose (CMC). However, in order to take full advantage of the enzymatic hydrolysis the enzyme selectivity on the cellulose substrate must be further investigated. Therefore, the selectivity of Tr Cel45A on CMC was studied by chemical sample preparation of the enzyme products followed by mass spectrometric chemical structure characterization. The results strongly suggest that, in accordance with recent studies, also this highly selective endoglucanase is able to catalyze hydrolysis of glucosidic bonds adjacent to mono-substituted anhydroglucose units (AGUs). Furthermore, the results also indicate that substituents on the nearby AGUs will affect the hydrolysis.
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| 6. |
- Enebro, Jonas, 1979-, et al.
(författare)
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Liquid Chromatography combined with Mass Spectrometry for the Investigation of Endoglucanase Selectivity on Carboxymethyl Cellulose
- 2009
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 344:16, s. 2173-2181
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Tidskriftsartikel (refereegranskat)abstract
- Endoglucanases are useful tools in the chemical structure analysis of cellulose derivatives. However, knowledge on the endoglucanase selectivity, which is of central importance for data interpretation, is still limited. In this study, new reverse-phase liquid chromatography mass spectrometry (LC-MS) methods were developed to investigate the selectivity of the endoglucanases Cel5A, cel7B, Cel45A, and Cel74A from the filamentous fungus Trichoderma reesei. The aim was to improve the identification of the regioisomers in the complex mixtures that are obtained after enzymatic hydrolysis. Reduction followed by per-O-methylation was performed in order to improve the separation in reverse-phase LC, increase MS sensitivity, and to facilitate structure analysis by MS/MS of O-carboxymethyl glucose and cellooligosaccharides. The cellulose selective enzymes that were investigated displayed interesting differences in enzyme selectivity on CMC substrates.
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| 7. |
- Enebro, Jonas, 1979-
(författare)
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New Mass Spectrometric Methods for Structure Analysis of Carboxymethyl Cellulose
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carboxymethyl cellulose (CMC) is a cellulose derivative, made from cellulose by introduction of carboxymethyl groups along the molecules. The properties of CMC are affected by several parameters where the molar mass and molar mass distribution, degree of substitution (DS) and the distribution pattern along, and between, the cellulose molecules are the most prominent. In the present thesis we have investigated the use of various mass spectrometric techniques, such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and electrospray ionization MS (ESI-MS), for characterization of the chemical structure of CMC. We here present a refined sample preparation procedure for MALDI that greatly facilitates the spectrum acquisition and improves the quality of the mass spectrum when analyzing partially hydrolyzed CMC. The refined method allows for estimation of the DS in CMC samples as a complement to more expensive and laborious methods. We also show that by combining MALDI-TOFMS with selective hydrolysis, by purified endoglucanase, and size-exclusion chromatography (SEC) it is possible to differentiate between CMCs of similar monomer composition but differences in the substitution pattern. Our findings show that the CMC containing longer non-substituted cellulose segments along the polymer backbone also displayed the highest intermolecular interactions in solution, as measured by rheometry. In order to take full advantage of the selective hydrolysis, provided by purified endoglucanases, more information regarding their selectivity on CMC must be investigated. We therefore present methods where chemical sample preparation of the oligomeric enzyme products is performed in order to facilitate the chemical structure characterization by ESI-MS/MS and liquid chromatography MS (LC-MS). These methods provides valuable information regarding the substituent distribution along the oligomeric enzyme products, and thereby gives indications regarding the selectivity of the endoglucanases on CMC substrates. From our finding we are able to present interesting information regarding the selectivity of four endoglucanases (Cel7B, Cel5A, Cel45A and Cel74A) from the filamentous fungus Trichoderma reesei and provide plausible explanations to their apparent differences in selectivity on CMC.
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| 8. |
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| 9. |
- Jakubowicz, Ignacy, et al.
(författare)
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Challenges in the search for nanoplastics in the environment—A critical review from the polymer science perspective
- 2021
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Ingår i: Polymer testing. - : Elsevier Ltd. - 0142-9418 .- 1873-2348. ; 93
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Tidskriftsartikel (refereegranskat)abstract
- Nanoplastics (NPs), which we define in this paper as solid plastic particles with the size <1 μm, unintentionally produced from the degradation and fragmentation of larger plastic objects are probably the least known area of plastic litter but are suspected to pose the greatest risk to the environment. However, no NPs have been detected in natural environments to date. This review attempts to provide a critical overview from the polymer science perspective of the relevant scientific literature, which could facilitate finding secondary NPs in natural environments. The information on secondary NPs has been scarce due to the big challenges in sampling, separation, and detection of these nanoscale particles. This review highlights the most important challenges and obstacles and discusses the mechanisms of generation of secondary NPs. It provides also a critical overview on modern instrumentation, newly developed workflows, promising techniques for sampling and sample preparation, and detection methods including spectroscopies (Raman and FT-IR), microscopies (SEM and TEM) and mass spectrometry (GC–MS and ToF–SIMS). We conclude that finding NPs in natural environments is plausible yet uncertain, which drives towards the development of a methodology for collection, separation and identification of NPs in environmental matrices along with a thorough evaluation of the process of formation of secondary NPs, their fate and effects on living organisms and the environment. To find nanoplastics in natural environments it is important to know the process of their formation, their fate, and experimental constraints.
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| 10. |
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