Nitrocellulose fractionation

Fig. 106. Nitrogen contents of extracted nitrocellulose fractions according to G. G. Jones and Miles [16a] CO HH nitrocellulose, 12.20% N, high viscosity, unkiered (II) HX nitrocellulose, 12.26% N, low viscosity (III) HX nitrocellulose, 12.07% N, low viscosity (IV) Guncotton, unkiered, 13.14% N (V) Guncotton, kiered, 12.95% N (VI) Guncotton, kiered, 12.93% N (VII) Pyro nitrocellulose, 12.70% N (VUI) Nitro-woodpulp, 11.30% N (IX) Nitroramie (73.5% soluble...

Fig. 108. Chromatographic separation of nitrocellulose fractions (quantity of fractions in mg/g and their molecular weight Af Claesson [116]).

These opposing tendencies may defeat the purpose of the fractional precipitation process. The fractional precipitation of crystalline polymers such as nitrocellulose, cellulose acetate, high-melting polyamides, and polyvinylidene chloride consequently is notoriously inefficient, unless conditions are so chosen as to avoid the separation of the polymer in semicrystalline form. Intermediate fractions removed in the course of fractional precipitation may even exceed in molecular weight those removed earlier. Separation by fractional extraction should be more appropriate for crystalline polymers inasmuch as both equilibrium solubility and rate of solution favor dissolution of the components of lowest molecular weight remaining in the sample. 

Figure 1. Electrophoretic profiles ofglucan synthase fractions purified from red beet. Proteins were transferred to nitrocellulose and stained by colloidal gold followed by silver overlay. Lane 1, solubilized enzyme (CSGS) Lane 2, reconstituted glucan synthase (RCGS).

Figure 2. Electrophoretic profiles of glucan synthase fractions purified from celery. Proteins were transferred to nitrocellulose and stained by colloidal gold. Symbols PM, plasma membranes SOL, CHAPS-solubilized RC, reconstituted glucan synthase preparations. Plasma membranes were isolated by two-phase partitioning. Specific activities of the three membrane preparations were 398, 1355, and 626 nmol/min/mg, respectively. The low specific activity of RC relative to SOL may be a reflection of enzyme instability following the gel filtration step.

The specific labeled separated protein fractions blotted on a nitrocellulose membrane or specific immunoflxation-separated protein fractions in polyacrylamide after isoelectric focusing make it possible to detect some additional bands in CSF, i.e., IgM, IgA, free kappa or lambda light chains of specific antibodies (i.e., antiherpes, anti-borrelia, or anti-HIV) (LI, M3). 

FIG. 3.5. Plots of ir/RTc versus concentration (a) various cellulose acetate fractions in acetone (data from A. Bartovics and H. Mark, J. Am. Chem. Soc., 65, 1901 (1943)) and (b) nitrocellulose in three different solvents (data from A. Dobry, J. Chem. Phys., 32, 50 (1935)). 

Alcohol from dehydration contains a certain quantity of nitrocellulose, i.e. its soluble fractions, mostly degraded, and a certain amount in suspension. Experiments have shown that about 2.2 g of dissolved nitrocellulose and 1.3 g of nitrocellulose in suspension—a total 3.5 g—occur in 11. of 70% alcohol from centrifuges. Sometimes however, the content of nitrocellulose in the alcohol may reach 10-12 g/1. 

Nitrocellulose granules, partially colloided, of sizes ranging from a few microns to a fraction of millimetres are suggested. The best known of the described methods was developed by the Hercules Powder Company [54]. It uses densified nitrocellulose originally developed for the lacquer industry, with an average particle size of 0.25 mm. 

The solubility of nitrocellulose in a solvent is defined by the percentage in this nitrocellulose of the fraction soluble in the solvent in question. 

In more recent experiments, Edelmann [95] has followed the depolymerization of nitrocellulose in dilute (0.5%) solution. He reported that nitrocellulose of an average polymerization degree n = 1060, and containing considerably amounts of the n > 2500 fraction, was degraded after being subjected for 1 and 4 hr to the action of ultrasonic waves of 800 kc/sec to an average polymerization degree of n = 910 and 630 respectively. By fractionation, the presence of a small quantity of n = 1400 was established in the latter. 

Long ago it has been established that nitrocellulose is not a homogeneous substance. The earliest experiments in this field were made by Stepanov [100] who used the method of fractional precipitation from an acetone solution by the addition of water. Stepanov added different amounts of water stepwise to a solution of nitrocellulose in acetone to obtain fractions varying slightly, corresponding with the nitrogen content. The first and least soluble fraction contained 13.15% of nitrogen, while the N-content of the last, fifth portion, was 12.90%. 

Duclaux et al. [101] came to other conclusions for he established that particular fractions differed only in the viscosity of solutions the nitrogen content being the same. In order to precipitate nitrocotton from its acetone solutions the authors added acetone-water mixtures, richer and richer in water until finally pure water was added. A range of fractions was separated from nitrocellulose acetone solution of viscosity 0.1 P (poises). The viscosity of the first fraction was 0.603 P, and that of the last 0.007 P (2% solutions). 

Identical results of fractionating nitrocellulose by successive dissolution and precipitation have also been reported by other authors, e.g. Brunswig [102] Kumi-chel [103], Lacape [55], Glikman [104]. 

In other experiments, the opposite method of fractionation by dissolution was applied. In this way G. Meissner [107] prepared a soluble fraction with a nitrogen content of 10.28%, in quantity about 4% by extracting a specimen of nitrocellulose with 12.17% N using 50 50 ether-alcohol. The insoluble part was composed of nitrocellulose of 12.32% N. 

Nitrocellulose has also been extracted with alcohol, the residue then being treated with a mixture of ether and ethanol (60 40 by volume, Berl and Hefter [108]). Three fractions were isolated the first soluble in alcohol, the second soluble in ether-alcohol, and the third an insoluble residue. The fractions differed in nitrogen content. The lowest nitrogen content was found in the first fraction and the highest in the third fraction (Table 58). 

Nitrogen content of original nitrocellulose Solubility, % Nitrogen content of fractions, % ... 

Extensive research into the fractional partition of nitrocellulose by means of acetone-water mixtures was carried out by Rogovin and Glasman [111]. The results of these experiments are given in the Table 59. 

Kruger [113] tried fractionating nitrocellulose by diffusion. The principle of the method was that a nitrocellulose solution in acetone, methyl alcohol or amyl acetate diffused into a pure solvent layer on the surface of the solution. Clearly molecules of smaller size penetrate more rapidly. A nitrocellulose solution of 12.8% N was separated into two layers in this way after 42 days diffusion. The lower fraction comprised nitrocotton with a nitrogen content of 13.1% N, the upper layer one of 12.1% N. 

The fractionating of nitrocellulose by chromatographic absorption has also been described. As reported by Claesson [116] a 1.5% nitrocellulose solution in... 

Western blotting has become an important, modern technique for analysis and characterization of proteins. The procedure consists of, first, the electrophoretic transfer (blotting) of proteins from polyacrylamide gels to synthetic membranes. The transferred blots are then probed using immunological detection methods to identify proteins of specific structure and/or function. In this experiment, bovine serum will be fractionated by SDS-PAGE and the proteins blotted onto a nitrocellulose membrane. Serum glycoproteins will be identified by their specific interaction with the lectin concanavalin A. 

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