Cellulose extraction

The amount of cellulose in lignocellulosic systems, can vary depending on the species and age of the plant. Table 21.1 shows the chemical composition of some common natural plant fibers. 

However, there are some methods for extraction of cellulose from plants. Han and Rowell s (1996) method describes a procedure for extraction of holocellulose, hemicelluloses, cellulose and lignin [18]. The method consists of four principle steps (1) preparation of sample (grinding of the wood), (2) removal of extractives, (3) preparation of holocellulose (removal of lignin), (4) preparation of a-cellulose (removal of hemicellulose). Several other procedures for a-cellulose extraction from wood samples have already been described during the last decades. Older methods used benzene-methanol instead of toluene-ethanol as organic solvent for the second step. Toluene-ethanol works as well as benzene-methanol mixture, and reduces health risks associated with the use of benzene and methanol. 

The method of Sheu and Chiu (1995) involves two main steps (1) extraction with benzene-ethanol in a soxhlet extractor for 12 hours, followed by (2) bleaching and soaking in NaClO -CHjCOOH solution. At the end of the procedure, they also soaked their cellulose in distilled water at 70°C for 6 hours [22]. As cited in [22], Loader et al. (1997) also presented a method in which they cut samples into fine slivers (-40 mm) and use organic solvent (2 1 toluene-methylated spirit azeotrope) only for softwood. Finally, samples take place in an ultra-sonic bath, which enhances the removal extracts. 

In addition, Borella et al. (2004) presented a method that is quite similar to Han and Rowell s (1996) method. They foxmd that fine milling the samples is very important for (1) avoiding sample inhomogeneity leading to increased measurement uncertainty, and (2) permitting complete a-cellulose extraction. 

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Polymers. Hydrocarbons from petroleum and natural gas serve as the raw material for virtually all polymeric materials commonly found in commerce, with the notable exception of rayon which is derived from cellulose extracted from wood pulp. Even with rayon, however, the cellulose is treated with acetic acid (qv), much of which is manufactured from ethylene (see Fibers, regenerated cellulosics). 

The first recommended soil method for oxime carbamates is the method of Honing et al. by HPLC/MS. The LOQ of the method, specifically for aldicarb, methomyl, and oxamyl, is 0.05mgkg. Soil (lOg) is Soxhlet extracted for 16h with acetone-dichloromethane (1 1) using double-thickness cellulose extraction thimbles (80 X 22-mm i.d.). Prior to extraction, the Soxhlet system and the thimbles are cleaned for 14 h by refluxing with methanol. The extracts are removed and concentrated nearly to dryness in a rotary evaporator operating at 35 °C evaporation to dryness... 

Weigh a finely ground representative crop sample (20 g for grain or 10 g for straw) into a cellulose extraction thimble. Assemble a Soxhlet extractor using a 500-mL round-bottom flask containing 200 mL of acetone and boiling chips. Place the extraction... 

Epstein S, Yapp CJ, Hall JH (1976) The determination of the D/H ratio of non-exchangeable hydrogen in cellulose extracted from aquatic and land plants. Earth Planet Sci Lett 30 241-251 Epstein S, Thompson P, Yapp CJ (1977) Oxygen and hydrogen isotopic ratios in plant cellulose. Science 198 1209-1215... 

Cellulose extraction thimbles and glass wool Condenser... 

Weigh exactly 20 ae 1 g of sample into cellulose extraction thimbles. Cover the top of each thimble with glass wool to prevent floating. 

Cellulose extraction thimble Cotton wool plug Heating mantle Soxhlet apparatus 30°C forced air oven... 

Weigh accurately 5.0 g of starch into a cellulose extraction thimble and cover the mouth with a cotton wool plug. 

With tanning extracts adulterated with cellulosic extracts, the indirect method does not, however, give reliable results, since cellulosic extracts contain non-tannins which are fixed by the hide powder. In such a case the tannin should be determined by the direct method, since these non-tannins have no appreciable action on permanganate the difference between the results of the two methods will give an approximate indication of the extent of the adulteration, if this is at all marked. 

As regards extracts, their composition varies greatly according both to the methods of preparation and purification and to the degree of concentration. With these the possibility of adulteration, especially with glucose, molasses, cellulose extracts and mineral salts, is to be considered. Addition of sulphurous anhydride or sulphites is allowed, for either clarification or preservation of the extract the proportion of total sulphurous acid may reach and even exceed 2%. 

Table IV. Viscosity of Cotton Cellulose Extracted with Various...

Activation of amino-a-carboline, 2-amino-l -methyl-6-phenylimidazo[4,5-fcjpyridine, and a copper phthalocyanine cellulose extract of cigarette smoke condensate by cytochrome P-450 enzymes in rat and human liver microsomes. Cancer Res., 51, 5284-5291. 

The proportion of cellulose extracted by the chloroform treatment has also been determined, and it turns out to be very small (less than 4%). The cellulose molecules must thus be arranged alternately in crystalline and amorphous zones. The proportion of cellulose that is wholly amorphous is very small, since only 4% of fi ee acetylated... 

Although samples are vacuum-dried during the process of cellulose extraction (see above), it has been demonstrated that moisture is readily absorbed from the air (Edwards et ah, 1994). Furthermore, due to the small sample size, any moisture can have a significant effect on the final analysis. It is therefore important to adhere to the following procedure designed to remove all traces of atmospheric moisture that may cause sample contamination. 

Edwards, T. W. D., R. J. Elgood B. B. Wolfe, 1997. Cellulose Extraction from Lake Sediments for... 

Chauhan, G. S., Mishra, B. N., Dhiman, S. K., Guleria, L. K., and Kaur, I. (2000). Polymers from renewable resources Kinetics of 4-vinyl pyridine radiochemical grafting onto cellulose extracted from pine needles, Radiot h em., 58,181-190. 

Viscose fibers - also known under the name rayon -are mamnade cellulosic fibers. Cellulose - extracted from wood (wood pulp) - reacts with 18% caustic soda to give alkali cellulose, which is treated with carbon disulfide after the so-called preripening (breakdown of the cellulose molecules into smaller units), the white alkali cellulose changing into orange—yellow cellulose xanthogenate. Diluted... 

Table 14.1 Mechanical properties of NR films reinforced with cellulose nanocrystals and microfibrils (MF) cellulose extracted from the date palm tree obtained from the tensile tests Young s modulus ( ), strain at break ( R) and strength.

As shown in Figure 21.7, at first, kenaf fiber was prepared from the bast part of kenaf stems. The cellulose extraction of kenaf fiber was then carried out using the Han and Rowell method [18]. Since cellulose is very hygroscopic material, the obtained cellulose was packed imder vacuum packaging. Cellulose and the other materials were blended in the internal mixer and were then compressed using the hot press machine to be converted into sheet form. Finally, the sheet forms of treatments were evaluated by standard tests [21]. 

S. BoreUa, G. Menofi md M. Leuenberger. Scunple homogeneity md cellulose extraction from plant tissue for stable isotope jmcdyses, in Handbook of stable isotope analytical techniques, P.A. Groot, (Ed.), Voliune 1, pp. 507-522, Elsevier (2004). 

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