Silylation, cellulose

Figure 7.3.6. Total ion chromatogram for pyrofysed hydroxypropyl methyl cellulose silylated and separated on a DB5 column.

Figure 1. Cellulose silylation with hexame yldisilazane in liquid anounonia. ...

Figure 2. Cellulose Silylation with Hexamethyldisilazane in Liquid Ammonia [33]...

Notes Cellulose (Whatman) PTMSP, poly(trimethyl silyl propine) PS, polystyrene PP, polypropylene PE, polyethylene PA 66, polyamide 66 PA 6, polyamide 6 PVP, poly(vinyl pyrrolidone) PPO, poly(2,6-dimetyl-l,4-phenylene oxide) PMMA, poly(methyl methacrylate) PETP, polyethylene terephthalate) Irganox 1010 is a Ciba anti-oxidant. 

D. Fabbri, G. Chiavari, S. Prati, I. Vassura and M. Vangelista, Gas chromatography/mass spectrometric characterisation of pyrolysis/silylation products of glucose and cellulose, Rapid Commun. Mass Spectrom., 16, 2349 2355 (2002). 

Urea in kidney dialysate can be determined by immobilizing urease (via silylation or with glutaraldehyde as binder) on commercially available acid-base cellulose pads the process has to be modified slightly in order not to alter the dye contained in the pads [57]. The stopped-flow technique assures the required sensitivity for the enzymatic reaction, which takes 30-60 s. Synchronization of the peristaltic pumps PI and P2 in the valveless impulse-response flow injection manifold depicted in Fig. 5.19.B by means of a timer enables kinetic measurements [62]. Following a comprehensive study of the effect of hydrodynamic and (bio)chemical variables, the sensor was optimized for monitoring urea in real biological samples. A similar system was used for the determination of penicillin by penicillinase-catalysed hydrolysis. The enzyme was immobilized on acid-base cellulose strips via bovine serum albumin similarly as in enzyme electrodes [63], even though the above-described procedure would have been equally effective. 

The DEAE cellulose is then hydrolyzed to substituted glucoses and glucose, which are silylated. The relative quantities of OH-2, OH-3, and OH-6 DEAE glucose are determined via gas chromatography. The fraction of total reactivity under these conditions for each of these hydroxyls is given in Table 5.4. 

Cellulose acetate butyrate and hydrolyzable silanes were reacted at 80 C for 10 h to give a silyl group-modified CAB for coating application [154]. 

Figure 5.2.15. The chromatogram of a silylated cellulose pyrolysate obtained off-line at 51Cf C with a filament flash pyrolyser.

Spectra interpretation can also be done by utilizing additional information, such as Cl spectral information for the same compound, etc. One useful procedure applied for example for the analysis of the pyrolysate of cellulose [45bJ is to use derivatization with BSTFA and derivatization with d9-BSTFA. The retention times in the GC/MS trace are practically not different for the material silylated by the two reagents. However, the two spectra corresponding to one derivatized material are different, and the difference... 

Cellulose pyrolysis has been studied in detail from a variety of points of view mainly related to chemical utilization of wood pyrolysis products or to fire related problems. Analytical pyrolysis of cellulose is not often used as a tool for cellulose detection, but it is a common procedure for studying the pyrolysis products. A variety of analytical procedures have been applied for this study, pyrolysis/gas chromatography/mass spectrometry (Py-GC/MS) being the most common [11-16]. Besides Py-GC/MS, other analytical procedures also have been utilized, such as Py-MS [17,18], Py-IR [19], and off-line Py followed by HPLC [20]. The Py-MS spectrum of cellulose was shown in Figure 5.4.1 (B). Some procedures applied GC/MS on derivatized pyrolysis products (off-line), the derivatization being done by silylation [21], permethylation, perbenzoylation [22], etc. Information about cellulose also has been obtained from the analysis of pyrolysis products of several cellulose derivatives, such as O-substituted cellulose [23]. Also the study of cellulose crystalline structure with X-ray during pyrolysis has been used [23a] to generate information about the pyrolysis mechanism. 

The chromatographic trace shown in Figure 7.2.1 was obtained from the cellulose pyrolysate generated at 590° C followed by off-line silylation with bis(trimethylsilyl) trifluoroacetamide (BSTFA). 

Figure 7.2.1. Cellulose pyrolysate obtained at 59CP C and trimethylsilylated. The separation was done on a methyl silicone with 5% phenyl silicone type column. 1 1,2-dihydroxyethane, 2 2-hydroxypropionic (lactic) acid, 3 hydroxy acetic (glycolic) acid, 4 turanmethanol, 5 peak from silylation reagents, 6 1,3-dihydroxypropanone, 7 1,4-dioxane-2,5-diol, 8 1,3-dioxolane-4,5-diol, 9 1,3-dihydroxybenzene, 10 2-methyl-1,4-dioxane-2,5-diol, 11 1,4-dihydroxybenzene, 12 3-hydroxy-2-(hydroxymethyl)-2-cyclopenten-1-one, 13 2-hydroxy-5-(hydroxymethyl)-4(H)-pyran-4-one, 14 1,2,3-trihydroxybenzene, 15 internal standard, 16 an anhydrosugar, 17 levoglucosan (1,6-anhydro-p-D-glucopyranose), 18 a monosaccharide, 19 an anhydrosugar, 20 an anhydrosugar, 21 1.6-anhydro-P-D-glucofuranose .

The characteristic ions for some peaks shown in Figures 7.2.1, 7.2.2 and 7.2.3, which were identified in the silylated pyrolysates of cellulose, are given in Table 7.2.2. 

Figure 7.2.5. Upper trace A TIC for cellulose pyrolysate obtained at 59(f C and silylated, identical to the trace shown in Figure 7.2.1 (some peak identifications can be obtained by comparing the retention times and the shape of the chromatograms).

Table 7.3.8. Peaks identified in the TiC of hydroxypropyi methyl cellulose pyrolysate silylated and separated on a DBS column.

Table 16.2.7. Peak identifications for the chromatogram of silylated smoke from a commercial cigarette (continued). Chromatogram from Figure 16.2.3 tentative source of individual components obtained by pyrolysis is also shown. (SM = small molecules Ps = polysaccharides including cellulose, pectins, hemicellulose etc. AP=amidated pectin Pr = protein Ma = Maillard polymers.)...

The separation characteristics of a considerable variety of other TLC supports were also tested using different dye mixtures (magnesia, polyamide, silylated silica, octadecyl-bonded silica, carboxymethyl cellulose, zeolite, etc.) however, these supports have not... 

Ionic liquids have also been used as solvents in other cellulose derivatisation reactions including etherification [166], carboxymethylation [160], phthalation [167, 168], sulfation [169], sulfonation [169], carbanilation [159, 162], silylation [170], succinylation [171], tritylation [172] and tosylation [173],... 

CMA involves five steps(14,16,18) a) reaction of cellulose with N, N-diethylaziridiniun chloride [DBC, Figure 2], b) total hydrolysis of the DEAE-cellulose to glucose and DEAE-glucoses, c) fermentation to remove the unmodified glucose, d) silylation of the DEAE-glucoses, and e) gas-liquid chromatograf ic analysis. 

K. Petzold, A. Koschella, D. Klemm, and B. Heublein, Silylation of cellulose and starch—selectivity, structure analysis, and subsequent reactions. Cellulose, 10 (2003) 251-269. 

W. Mormann, J. Demeter, and T. Wagner, Partial silylation of cellulose with predictable degree of silylation—Stoichiometric silylation with hexamethyldisi-lazane, Macromol. Chem. Phys., 200 (1999) 693-697. 

Native cellulose are commonly modified by physical, chemical, enzymic, or genetic means in order to obtain specific functional properties, and to improve some of the inherent properties that limit their utility in certain application. Physical/surface modification of cellulose are performed in order to clean the fiber surface, chemically modify the surface, stop the moisture absorption process, and increase the surface roughness. " Among the various pretreatment techniques, silylation, mercerization, peroxide, benzoylation, graft copolymerization, and bacterial cellulose treatment are the best methods for surface modification of natural fibers. 

Gousse, C., Chanzy, H., Excoffier, G., Soubeyrand, L., and Fleuiy, E. (2002). Stable suspensions of partially silylated cellulose whiskers dispersed in organic solvents, Po/ 22 v 4-3,2645-2651. 

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