Cellulose phases preparation

Figure 2. Nematic phase patterns formed in the cellulose solutions prepared from solvent composition of 24.5/75.5 cellulose concentration, 14g/100mL DP, 450 (a and b) immediately after dissolution.

Figure 9. Electron mlcrophotograph of the dry regenerated cellulose membrane prepared through micro-phase separation method primary particles are observed In a secondary particle with a diameter of ca. 300 nm.

The pore size distribution N(r), experimentally determined for the regenerated cellulose membrane prepared through the micro-phase separation method, is compared with the theoretical N(r) in Figure... 

Hirai, A., Inui, O., and Horii, F. (2008). Phase separation behavior in aqueous suspensions of bacterial cellulose nanocrystals prepared by sulfuric acid treatment, Lanamuir. 25(1), 497-502. 

X-ray investigations showed that in contrast to CNP, the cellulose particles prepared after regeneration from 65 to 66 wt% SA possessed a diffuse X-ray dif-fractogram typical for the amorphous phase state (Figure 9.11). 

Acetylated cellulose plates, prepared by esterification of cellulose with acetic acid or acetic anhydride, are used for reversed-phase TLC. Plates are available with varying degrees of acetylation ranging from 10 to 40% the polarity of the layer decreases with increasing acetylation. Enantiomeric compounds were resolved by RP-TLC on microcrystalline triacetyl cellulose using 2-propanol-water (6 4) as the mobile phase (Lepri, 1995). 

The CNTs-fiUed cellulose nanocomposites prepared with various fabrication techniques included phase inversion, vacuum filtration, and flash freezing (Li et al. 2013a, b, c, d, e Qi et al. 2013a, b, c El Badawi et al. 2014). The CNTs-filled... 

The availabihty of spray-dried lactose, microcrystaUine cellulose, and other excipients allows for the use of granular rather than powdered phases. This eliminates some of the problems of particle segregation according to size (demixing) and even flow to the die. Direct compression eventually may be the preferred method of tablet preparation. 

In this context, the enantiomeric pair containing the eutomer of cyclothiazide can be resolved by HPLC on cellulose-derived coated CSPs. Nevertheless, the poor solubility of this compound in solvents compatible with this type of support makes this separation difficult at preparative scale. This operation was achieved with a cellulose carbamate fixed on allylsilica gel using a mixture of toluene/acetone as a mobile phase [59]. 

A precursor in the synthesis of a promising calcium sensitizing agent from E. Merck [33], a chiral thiadiazin-2-one EMD 53986, 3,6-Dihydro-5-[l,2,3,4-tetrahy-dro-6-quinolyl]-6-methyl-2H-l,3,4-thiadiazin-2-one [26]. The study was performed using Celluspher , a CSP prepared from cellulose tri(p-methylbenzoate) according to a patent from Ciba-Geigy [34]. The spherical particles had a mean particle diameter of 20 3 pm and the mobile phase was pure methanol. 

The analysis of a pharmaceutical tablet (6) requires sample preparation that is little more complex as most tablets contain excipients (a solid diluent) that may be starch, chalk, silica gel, cellulose or some other physiologically inert material. This sample preparation procedure depends on the insolubility of the excipient in methanol. As the components of interest are both acidic and neutral, the separation was achieved by exploiting both the ionic interactions between the organic acids and the adsorbed ion exchanger and the dispersive interactions with the remaining exposed reverse phase. 

Some part of the cellulose fraction is redirected to make cellulose derivatives, such as cellulose acetate, methyl and ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. These derivatives find multiple applications, for instance, as additives in current products (e.g., paints, lacquers) of chemical industry. Typically, the preparation of cellulose derivatives takes place as a two-phase reaction cellulose is pretreated, for example, with alkali, and a reagent is added to get the substitution. Usually no catalyst is needed [5]. 

These aspects of solvent property similarly apply to precoated impregnated silica gel plates, e.g., by ammonium sulfate, silver nitrate, or magnesium acetate, as well as to microcrystalline cellulose precoated plates. On preparative RP phases, water has the lowest elution power. Therefore, more polar or aqueous solvents should be preferred. In contrast to HPTLC RP-18 layers, on which such aqueous solutions remain as a drop on the surface and are not able to penetrate through the lipophilic layer, on preparative RP phases, pnre aqneons application solutions can be apphed owing to the minor degree of C18 modification. 

Of course, preparative or semipreparative separation of substances of clinical interest is realized not only on silica gels or impregnated silica gels, but favorable results are also obtained on different stationary phases (e.g., cellulose or ion exchangers). 

A modified nucleotide found in RNA sequencing could either be a new nucleotide of unknown chemical structure or it could correspond to an already known modified nucleotide (up to now about 90 different modified nucleotides have been identified in RNA). Keith [124] proposed preparative purifications of major and modified ribonucleotides on cellulose plates, allowing for their further analysis by UV or mass spectrometry. Separation was realized by two-dimensional elution using the following mobile phases (1) isobutyric acid-25% ammonia-water (50 1.1 28.9,... 

There is a wide variety of commercially available chiral stationary phases and mobile phase additives.32 34 Preparative scale separations have been performed on the gram scale.32 Many stationary phases are based on chiral polymers such as cellulose or methacrylate, proteins such as human serum albumin or acid glycoprotein, Pirkle-type phases (often based on amino acids), or cyclodextrins. A typical application of a Pirkle phase column was the use of a N-(3,5-dinitrobenzyl)-a-amino phosphonate to synthesize several functionalized chiral stationary phases to separate enantiomers of... 

Online detection using 4H nuclear magnetic resonance (NMR) is a detection mode that has become increasingly practical. In a recent application, cell culture supernatant was monitored on-line with 1-dimensional NMR for trehalose, P-D-pyranose, P-D-furanose, succinate, acetate and uridine.33 In stopped-flow mode, column fractions can also be analyzed by 2-D NMR. Reaction products of the preparation of the neuromuscular blocking compound atracurium besylate were separated on chiral HPLC and detected by 4H NMR.34 Ten isomeric peaks were separated on a cellulose-based phase and identified by online NMR in stopped-flow mode. 

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