Fractionation procedures for

Microwave extraction realized at 120 °C for 30 min with Hexane -Acetone (3 2 V/V) as the extraction solvent was identified as the most effective extraction procedure for isolation of TPH from biotic matrices. The aim of this research is to develop a silica gel and alumina fractionation procedure for plant sample extraction. Column chromatography with two solvents (chloroform and hexane dichloromethane) as a mobile phase were used for clean-up of extract. In this research the efficiency of recovery received from chloroform as a mobile phase. 

The methylene blue reaction can also be used in a fractionation procedure for surfactants. The complexes with methylene blue can be collected in an organic solvent, concentrated, dissolved in methanol, and separated by high-performance liquid chromatography [205]. A variation of this method, permitting the collection of surfactant from large volumes of sample, should be workable in seawater. 

Zinbo, M., D. Schuetzle, D. P. H. Hsieh, N. Y. Kado, J. M. Dasiey, and L. A. Gundel, An Improved Fractionation Procedure for the Bioassay-Directed Chemical Analysis of Ambient Air Particulate Extracts, Anal. Sci., 8, 461-468 (1992). 

The aims of protein purification, up until the 1940s, were simply academic. To then, even the basic facts of protein structure were not fully appreciated, and pure proteins were needed just to study structure and test the rival theories of the pre-DNA days. During the Second World War, an acute need for blood proteins led to development of the Cohn fractionation procedure for purification of albumin and other proteins from serum (Cohn et al., 1946). This was the inception of large-scale protein purifications for commercial purposes Cohn fractionation continues to be used to this day. 

Many different sample preparation procedures have been employed, ranging from simple filtration of juice products to solvent extraction, and extraction by SPE using C, 8, Sephadex LH-20 (49,50,52), and Amberlite XAD-2 (51,54,57). The Amberlite XAD-2 cleaning step has been used for many phenolic extracts, especially for fruit purees, to remove the sugars and other polar compounds. However, due to the low recovery rate with Amberlite XAD-2 for certain phenol glycosides, a modified sample preparation technique is needed, especially for quantification of ar-butin in pear juice and blends (54). Figure 6 describes the fractionation procedure for phenolics using a Sephadex LH-20 column (58). 

Klinkow, N. and M. Jekel. 1999. Use of toxicity-directed fractionation procedures for the localization and identification of toxicants in wastewater and environmental samples—a review. Vom Wasser 93 325-348. 

Leenheer and Huffman (1976) have developed a fractionation procedure for aquatic organic solutes called dissolved organic carbon (DOC) fractionation. The procedure for the analytical DOC fractionation is shown in Figure 3. Hydrophobic solutes are first removed from water by adsorption on Am-berlite XAD-8 resin, hydrophilic bases in the effluent are removed by cation-exchange resins, and hydrophilic acids in the effluent are removed by anion-exchange resins. Aquatic humic substances occur primarily in the... 

Stuber, H. A., and Leenheer, J. A. (1978). Assessment of a resin based fractionation procedure for monitoring organic solutes from oil shale retorting wastes. In Establishment of Water Quality Monitoring Programs, (L. G. Everett and Schmidt, K. D., eds.). American Water Resources Assoc., Minneapolis, MN, pp. 266-272. 

Isolated nerve endings (synaptosomes) in superfusion represent an ideal preparation for the study of neurotoxicant action. Indeed the use of such an approach to examine the interaction of pharmacological agents with ion channels in vertebrate synaptosomal preparations is well established ( 3), (40. It is only relatively recently that fractionation procedures for invertebrate synaptosomes have been optimized and superfusion techniques applied to the study of drug and toxin action in insects (J ), ( 5). In the present communication we have attempted to clarify the mode of action of certain insecticidal neurotoxicants by determining their effects on transmitter release in the presence and absence of channel specific modulators. 

Fortunately, at this time, there were developments in the techniques for the fractionation of macromolecules at a 1967 ACS Symposium, a review of the existing fractionation procedures for cellulases (4) revealed that, although notable successes had been achieved, better methods for the purification and characterization of the enzyme components were needed. Towards the end of 1961, developments in the production of gel-filtration media and of ion-exchange forms of the same materials made possible the application of these techniques to the separation of the components of the cellulase system. 

Chong, C.N., Hoh, Y.M., and Wang, C.W. 1992. Fractionation procedures for obtaining cocoa butter-like fat from enzymatically interesterified pahn olein, JAOCS, 69 137-140. 

SEC analysis can be used very effectively in combination with Corbett separation, solvent or supercritical solvent fractionation, and other fractionation procedures for the purpose of understanding asphalt composition and aging. Figure 2 shows chromatograms for an asphalt cut into a 60% top fraction and a 40% bottom fraction by supercritical pentane (15). The top 60% was fractionated into four fractions by supercritical pentane (Figure 3), and the bottom... 

Cell fractionation Details of the fractionation procedure for cytoplasmic material freed of nuclei and mitochondria has been described in detail in a previous publication [7]. However, a brief description is given in a chart (Figure 1). Figure 2 shows the densities of the sucrose in the linear gradient of each collected fraction. The fractions were collected by a peristaltic pump (Pharmacia Inc.) from the bottom of the tube containing subcellular particles. 

Much effort has been expended on the purification of the transfer RNA fraction as a whole, and on the separation of individual acceptor RNA s from each other. In general, earlier fractionation procedures for total cellular RNA have been lechecked in order to determine their applicability to the separation of sRNA from microsomal RNA. It was found that the fraction soluble in 1 AT NaCl (77, 78), and which is also eluted from ECTEOIA columns by neutral salt solutions, corresponds to sRNA. The same is true of the fraction which is soluble in cold absolute ethanol after precipitation of total RNA with cold TCA (79). Webster (76) has achieved a twelvefold purification in the over-all amino accepting ability of sRNA from pea seedlings by fractional precipitation with aqueous ethanol. 

A. Isolation and Determination of Lipids and Higher Fatty Acids. B. Preparation and itnalysis of Phospholipids and Derivatives. C. Fractionation Procedures for Higher and Lower Fatty Acids. D. Preparation and Assay of Cholesterol and Ergosterol. 

Because of their diversity and complexity as well as the gradual internationalization of the different standards, it has proven necessary to standardize the methods of sample preservation, handling, fractionation, and analysis throughout the chain of separation and treatment. All these stages are the object of precise protocols established by official national and international organizations. They describe in as minute detail as possible the procedures employed not only for each analysis but very often giving different procedures for the same analysis in different matrices. These are the standards or standardized methods discussed in Chapter 7. 

A procedure for determining the stoichiometry between two reactants by preparing solutions containing different mole fractions of one reactant also known as Job s method. 

Dual solvent fractional extraction (Fig. 7b) makes use of the selectivity of two solvents (A and B) with respect to consolute components C and D, as defined in equation 7. The two solvents enter the extractor at opposite ends of the cascade and the two consolute components enter at some point within the cascade. Solvent recovery is usually an important feature of dual solvent fractional extraction and provision may also be made for reflux of part of the product streams containing C or D. Simplified graphical and analytical procedures for calculation of stages for dual solvent extraction are available (5) for the cases where is constant and the two solvents A and B are not significantly miscible. In general, the accurate calculation of stages is time-consuming (28) but a computer technique has been developed (56). 

The early immunoglobulin products prepared by cold-ethanol fractionation were found to be free from transmitting hepatitis infection (106,108) this was not the case with products prepared by alternative methods (109). Subsequentiy, some batches of intravenous immunoglobulin transmitted hepatitis infection (110), emphasizing the importance of estabHshing vaHdated procedures for dealing with potential viral contaminants (111). 

The detergent method for insoluble fiber superseded the cmde fiber method and became the method of choice for insoluble fiber analysis until the 1980s, when methods were developed to recover soluble fiber as well. Some analysts still prefer the NDF procedure for insoluble fiber. The method is simple, inexpensive, reproducible, and amenable to routine assays. The disadvantage is the inabiUty to recover the soluble fraction. See Reference 14 for more information on detergent methods. 

One of the most widely applicable and most commonly used methods of purification of liquids or low melting solids (especially of organic chemicals) is fractional distillation at atmospheric, or some lower, pressure. Almost without exception, this method can be assumed to be suitable for all organic liquids and most of the low-melting organic solids. For this reason it has been possible in Chapter 4 to omit many procedures for purification of organic chemicals when only a simple fractional distillation is involved - the suitability of such a procedure is implied from the boiling point. 

Dried with Linde type 5A molecular sieves or Na2S04 and fractionally distd at reduced pressure. Alternatively, it was refluxed with, and distd from, BaO. Also purified by fractional crystn from the melt and distd from zinc dust. Converted to its phosphate (m 135°) or picrate (m 223°), which were purified by crystn and the free base recovered and distd. [Packer, Vaughn and Wong J Am Chem Soc 80 905 1958.] The procedure for purifying via the picrate comprises the addition of quinoline to picric acid dissolved in the minimum volume of 95% EtOH to yield yellow crystals which are washed with EtOH and air dried before recrystn from acetonitrile. The crystals are dissolved in dimethyl sulfoxide (previously dried over 4A molecular sieves) and passed through a basic alumina column, on which picric acid is adsorbed. The free base in the effluent is extracted with n-pentane and distd under vacuum. Traces of solvent are removed by vapour phase chromatography. [Mooman and Anton J Phys Chem 80 2243 1976.]... 

Most purification procedures for a particular protein are developed in an empirical manner, the overriding principle being purification of the protein to a homogeneous state with acceptable yield. Table 5.5 presents a summary of a purification scheme for a selected protein. Note that the specific activity of the protein (the enzyme xanthine dehydrogenase) in the immuno-affinity purified fraction (fraction 5) has been increased 152/0.108, or 1407 times the specific activity in the crude extract (fraction 1). Thus, xanthine dehydrogenase in fraction 5 versus fraction 1 is enriched more than 1400-fold by the purification procedure. 

Sulfates and nitrates are known and in all cases they decompose to the oxides on heating. Double sulfates of the type M (S04)3.3Na2S04.12H20 can be prepared, and La (unlike Sc and Y) forms a double nitrate, La(N03)3,2NH4N03.4H20, which is of the type once used extensively in fractional crystallization procedures for separating individual lanthanides. 

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