Fiber Extraction methods

Hot water retting (biological) Mechanical separation (physical) Chemical extraction (chemical) Enzymatical extraction (chemical) Ultrasonic separation (physical) Steam-explosion (physical) [56] 

In the course of these procedures, the non-cellulosic parts are removed in specific proportions and the cellulosic fibers are exposed and seperated [56]. Each method has its advantages and disadvantages in terms of the yield and quality of the extracted fibers 

---

Bodros and Baley [37] studied the tensile properties of water retted nettle fibers. Bacci et al. [39] investigated fiber yield of nettle cultivation and quality of fibers extracted by alkalization. Bacci et al. [38] compared the effects of different fiber extraction method combinations including water retting, mechanical decortication and enzymatic treatments on resultant fibers chemical composition and tensile properties. Bajpai et al. [40,41] prepared nettle fiber-reinforced poly lactic acid (PLA) and PP composites by compression molding. Bajpai et al. [42] studied the effects of various environments on the tensile strength of nettle fiber-reinforced PP composites. 

Table 11.1 List of Academic Literature on Agro-Residual Fibers, Extraction Methods, Studied Characterics. 

All bast (stem) fibers (flax, kenaf, ramie, nettle, hemp, jute) as well as hard fibers (caroa, sisal) are suitable as for reinforcing fibers for natural fiber reinforced polymer composites, if they have a high tensile modulus and sufficient tensile strength. In addition to cultivation site, type and harvest, the properties of natural fibers depend significantly on the fiber extraction method. An extraction to technical fiber grades, i.e. production of bundles with different number of single fibers, is generally sufficient for use in plastics composites. The properties of such extracted fibers may be described as follows ... 

Detergent Methods. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) methods (2), later modified for human foods (13), measure total insoluble plant cell wall material (NDF) and the cellulose—lignin complex (ADF). The easily solubilized pectins and some associated polysaccharides, galactomaimans of legume seeds, various plant gums, and seaweed polysaccharides are extracted away from the NDF. They caimot be recovered easily from the extract, and therefore the soluble fiber fraction is lost. 

Extraction methods, amounts, and lengths of various natural fibers and their physical and chemical properties are given in Tables 2 and 3. 

Table 2 Extraction Methods, Amount, and Length of Various Natural Fibers...

Headspace SPME is a solventless extraction method where a silica fiber coated with adsorbant or absorbant polymer material is exposed to a gas phase to extract analytes. The food of interest is placed in a closed or open container (such as a mouth simulator). After extraction, the fiber is desorbed in a GC injection port for separation and detection of the extracted analytes. 

Oil (Aa 4-38) determines oil content in a dried sample of oil-bearing material by extraction with petroleum ether. This method is specific for cottonseed, which first must be fumed with hydrochloric acid to prevent oil adsorption to the fiber. Additional methods exist for other oilseeds. Oxygen Stability Index (OSI) (Cd 12b-92) measures the oxidation induction period of fat sample (essentially the time for a sample to exhaust its antioxidant properties) under conditions of the test. 

The methodology developed to date has led to a marked improvement in the accuracy with which release rates can be measured from hollow fiber formulations. A careful combination of methods such as the combined use of the airflow and extraction methods discussed here with the appropriate combination of quantification methods will ultimately lead to a better understanding of the various factors affecting the release of materials from controlled release devices. 

Under normal conditions it would appear that the enzyme is secreted from cells in close association with its substrate. By conventional extraction methods (physiological buffers), most of the lysyl oxidase activity is not released from insoluble connective tissue fibers (33,34). It is only released after extraction with denaturants, such as urea. Further, it is difficult to handle in solution because of its tendency to form aggregates. 

In the grafting onto fibers or Aims, the homopolymer occluded in the grafting product is generally removed by extraction with a selective solvent TWs method is in itself relatively simple and hence the most widely used, though time-consuming. However, it is pointed out that an preciable amount of homopolymer is furthermore extracted if the unreacted substrate polymer has been previoudy removed. According to Staimett and collaborators the conventional extraction method is inadequate to obtain the pure graft copolymer free of homopolymers, unless both homopolymers are subjected to a repeated, alternate extraction. We have also revealed that the alternate extraction is necessary for separation in various cases . However, there are serious problems with respect to the extractability of homopolymers. 

Conditions for the optimization of SPME of phenol and chlorophenol soil contaminants were investigated end analysis was by GC-FID. The method was applied to soil analysis after acute contamination in industrial sites. The method was validated by comparison with an EPA certified extraction method . Soil samples were suspended in water and the extracted phenols were acetylated in situ with acetic anhydride in the presence of potassium bicarbonate. Acid was added after the end of the derivatization and SPME was performed by placing a poly(dimethylsiloxane) fiber in the headspace. End analysis was performed by introducing the fiber into the injector of a GC-MS apparatus. LOD was in the sub-ppm range, with good precision, sensitivity and linearity . ... 

Lezaniiz, J., Barri, T., Jonsson, J. A., Skog, K. (2008). A simplified hoUow-fiber supported hquid membrane extraction method for quantification of 2-amino-l-methyl-6-phenyhmidazo[4,5-b]pyridine (PhIP) in urine and plasma samples. Anal. Bioanal. Chem., 390, 689-96. 

HS-SPME-GC-MS showed that residual methyl methacrylate is released during thermal annealing of PMMA [40]. SPME fiber was carboxen/PDMS. The extraction time and temperature was 2 hours at 70 °C. A multiple headspace extraction method using a carboxen/PDMS fiber was developed for the quantitative determination of vinyl chloride monomer in PVC [41]. To reduce the equilibrium time, the PVC sample was finely ground before the extraction. Quantitative SPME methods have also been developed to determine vinyl chloride in liquid and solid samples [42] and to determine terephthalic acid and vinyl acetate monomers from aqueous solutions [43]. 

Solid-phase micro-extraction (SPME) first became available to analytical researchers in 1989. The technique consists of two steps first, a fused-silica fiber coated with a polymeric stationary phase is exposed to the sample matrix where the analyte partitions between the matrix, and the polymeric phase. In the second step, there is thermal desorption of analytes from the fiber into the carrier gas stream of a heated GC injector, then separation and detection. Headspace (HS) and direct insertion (DI) SPME are the two fiber extraction modes, whereas the GC capillary column mode is referred to as in-tube SPME. The thermal desorption in the GC injector facilitates the use of the SPME technology for thermally stable compounds. Otherwise, the thermally labile analytes can be determined by SPME/LC or SPME/GC (e.g., if an in situ derivatization step in the aqueous medium is performed prior to extraction). Different types of commercially-avarlable fibers are now being used for the more selective determination of different classes of compounds 100 /rm polydimethylsiloxane (PDMS), 30 /rm PDMS, 7 /rm PDMS, 65 /rm carbowax-divinylbenzene (CW-DVB), 85 /rm polyacylate (PA), 65 /rm PDMS-DVB, and 75 /rm carboxen-polydimethyl-siloxane (CX-PDMS). PDMS, which is relatively nonpolar, is used most frequently. Since SPME is an equilibrium extraction rather than an exhaustive extraction technique, it is not possible to obtain 100% recoveries of analytes in samples, nor can it be assessed against total extraction. Method validation may thus include a comparison of the results with those obtained using a reference extraction technique on the same analytes in a similar matrix. 

Advantages of SPME to traditional extraction methods should promote advances in the field of herbicide chemistry. However, SPME has some limitations, such as analyte carryover, fiber damage at extreme pH, salt-related problems, and low sensitivity in some complex soil samples. Advancements are being made in the refinement of the SPME technique. The HPLC/SPME interface has then been improved, and new mixed phases based on solid/liquid sorption (e.g., CW-DVB and PDMS-DVB) have been developed in recent years for the analysis of compounds by HPLC. A modified accessory to the HPLC system, called in-tube SPME, was developed. This device aspirates and dispenses samples from vials with the syringe in the inject position and then desorbs with aspirated solvent in the load position. Returning the valve to the inject mode will transfer analytes to the analytical column. ... 

---