| 1. |
- Liu, Jun, et al.
(author)
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Profiling the substitution pattern of xyloglucan derivatives by integrated enzymatic hydrolysis, hydrophilic-interaction liquid chromatography and mass spectrometry
- 2016
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In: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1463, s. 110-120
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Journal article (peer-reviewed)abstract
- Plant polysaccharides constitute arguably the most complex family of biomacromolecules in terms of the stereochemistry and regiochemistry of their intramolecular linkages. The chemical modification of such polysaccharides introduces an additional level of complexity for structural determinations. We have developed an integrated analytical procedure combining selective enzymatic hydrolysis, hydrophilic interaction liquid chromatography (HILIC), and mass spectrometry (MS) to describe the substitution pattern of xyloglucan (XyG) and its chemo-enzymatic derivatives (cationic, anionic, and benzyl aminated). Enzymatic hydrolysis of XyG derivatives by a xyloglucan-specific endoglucanase (XEG) generates oligosaccharides amenable for mass spectrometric identification with distinct structures, based on enzymatic substrate recognition and hydrolytic pattern. Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF-MS) and electrospray ionisation mass spectrometry (ESI-MS) offer qualitative mass profiling of the chemical derivatives. Separation and identification of the complex oligosaccharide profiles released by enzymatic hydrolysis is achieved by hyphenation of hydrophilic interaction liquid chromatography with mass spectrometry (HILIC-ESI-MS). Further fragmentation by tandem mass spectrometry (ESI-MS/MS) in positive mode enables the structural sequencing of modified XyG oligosaccharides and the identification of the substituent position without further derivatisation. This integrated approach can be used to obtain semi-quantitative information of the substitution pattern of hemicellulose derivatives, with fundamental implications for their modification mechanisms and performance.
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| 2. |
- Sullivan, Mitchell A., et al.
(author)
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Improving size-exclusion chromatography separation for glycogen
- 2014
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1332, s. 21-29
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Journal article (peer-reviewed)abstract
- Glycogen is a hyperbranched glucose polymer comprised of glycogen beta particles, which can also form much larger composite alpha particles. The recent discovery using size-exclusion chromatography (SEC) that fewer, smaller, alpha particles are found in diabetic-mouse liver compared to healthy mice highlights the need to achieve greater accuracy in the size separation methods used to analyze alpha and beta particles. While past studies have used dimethyl sulfoxide as the SEC eluent to analyze the molecular size and structure of native glycogen, an aqueous eluent has not been rigorously tested and compared with dimethyl sulfoxide. The conditions for SEC of pig-liver glycogen, phytoglycogen and oyster glycogen were optimized by comparing two different eluents, aqueous 50 mM NH4NO3/0.02% NaN3 and dimethyl sulfoxide/0.5% LiBr, run through different column materials and pore sizes at various flow rates. The aqueous system gave distinct size separation of alpha- and beta-particle peaks, allowing for a more detailed and quantitative analysis and comparison between liver glycogen samples. This greater resolution has also revealed key differences between the structure of liver glycogen and phytoglycogen.
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| 3. |
- Vilaplana, Francisco, et al.
(author)
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Analysis of brominated flame retardants in styrenic polymers : Comparison of the extraction efficiency of ultrasonication, microwave-assisted extraction and pressurised liquid extraction
- 2008
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1196:1-2, s. 139-146
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Journal article (peer-reviewed)abstract
- The extraction efficiency of pressurised liquid extraction (PLE), microwave-assisted extraction (MAE), and ultrasonic-assisted extraction (UAE) under different conditions has been compared for the recovery of the most commonly employed brominated flame retardants (BFRs) from styrenic polymeric Matrixes. A HPLC-MS/MS method has been proposed for the simultaneous separation and quantification of tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD) diastereomers, and decabromodiphenyl ether (deca-BDE) in the polymeric extracts. PLE results in complete extraction of TBBPA and HBCD (95-100% recovery), and intermediate recovery Fates for deca-BDE (50%). MAE, on the other hand, gives comparable performance to PLE for HBCD, but lower extraction yields for TBBPA and mainly deca-BDE. Ultrasonication, finally, offers relatively low extraction recoveries (10-50%). The proposed analytical procedures could be used for the effective identification and quantification of BFRs in styrenic plastics and for quality purposes in recycling facilities that deal with styrenic fractions from waste electrical and electronic equipment (WEEE).
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| 4. |
- Vilaplana, Francisco, et al.
(author)
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Analytical methodology for multidimensional size/branch-length distributions for branched glucose polymers using off-line 2-dimensional size-exclusion chromatography and enzymatic treatment
- 2011
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1218:28, s. 4434-4444
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Journal article (peer-reviewed)abstract
- Instrumental and procedural optimizations are developed for a new method to obtain 2-dimensional distributions for branched homopolymers based on size and branching. The method uses 2-dimensional off-line size-exclusion chromatography (SEC) and chemical debranching, in this case using debranching enzymes on branched glucose polymers. This treatment, first presented for the 2D weight and number distributions of starch [F. Vilaplana, R.G. Gilbert, Macromolecules 43 (2010) 7321] is applied here to give 2D weight distributions as functions of size and branch length for glycogen, amylose, and native starch containing both amylopectin and amylose. Completely dissolved polysaccharides are first fractionated by size (hydrodynamic volume) using preparative SEC; the collected fractions are then debranched by addition of isoamylase, and the size distributions of the corresponding branches are analyzed for each fraction using analytical SEC with differential refractive index and with multiple-angle laser light scattering detection. Operational parameters have been optimized to provide sufficient separation resolution for each dimension (size of the whole branched macromolecule and size of the resulting branches after debranching) and to minimize degradation. These 2-dimensional distributions bring out new features in the structure of these branched polysaccharides, and offer a useful tool to elucidate relations between biosynthesis, structure, and properties.
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| 5. |
- Vilaplana, Francisco, et al.
(author)
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Emission pattern of semi-volatile organic compounds from recycled styrenic polymers using headspace solid-phase microextraction gas chromatography-mass spectrometry
- 2010
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1217:3, s. 359-367
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Journal article (peer-reviewed)abstract
- The emission of low molecular weight compounds from recycled high-impact polystyrene (HIPS) has been investigated using headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass Spectrometry (GC-MS). Four released target analytes (styrene, benzaldehyde, acetophenone, and 2-phenylpropanal) were selected for the optimisation of the HS-SPME sampling procedure, by analysing operating parameters such as type of SPME fibre (polarity and operating mechanism), particle size, extraction temperature and time. 26 different compounds were identified to be released at different temperatures from recycled HIPS, including residues of polymerisation, oxidated derivates of styrene, and additives. The type of SPME fibre employed in the sampling procedure affected the detection of emitted components. An adsorptive fibre such as carbowax/polydimethylsiloxane (CAR/PDMS fibre) offered good selectivity for both non-polar and polar volatile compounds at lower temperatures: higher temperatures result ill interferences from less-volatile released compounds. An absorptive fibre as polydimethylsiloxane (PDMS) fibre is Suitable for the detection of less-volatile non-polar molecules at higher temperatures. The nature and relative amount of the emitted compounds increased with higher exposure temperature and smaller polymeric particle size. HS-SPME proves to be a suitable technique for screening the emission of semi-volatile organic compounds (SVOCs) from polymeric materials; reliable quantification of the content of target analytes in recycled HIPS is however difficult due to the complex mass-transfer processes involved, matrix effects, and the difficulties in equilibrating the analytical system.
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