Fractionation Schemes

Whatever the fractionation scheme used, the fraction is removed as overhead from the debutanizer. References 45 and 46 give ethylene manufacturing process. 

Fraetionation dissoeiation extraetion involves both the chemical reaction and the fractionation scheme for the separation of components by their difference in dissociation constants as described by Colby [in Hanson (ed.). Recent Advances in Liquid-Liquid Extraction, Pergamon, New York, 1971, chap. 4]. 

Our most recent work with B megapotamica has been with the isolation of large quantities of baccharinoids from a 1800 Kg collection. The workup of the crude extract (ca. 30 Kg of black tarry material) of this plant material was conducted by Dr. Fred Boettner of Polyscience, Inc. This near Herculean task required tremendous quantities of solvents, column packings and time to complete. An outline of the fractionation scheme is presented in Figure 2. Fractions F6-F11 contain a large number of baccharinoids. To date, we have characterized over twenty macrocyclic trichothecenes found in B mega-... 

Figure 1. Solvent Fractionation Scheme Using Silicon Gel Column for Crude Oil and Shale Oil.

These yields are also given on the basis of 100 g of original dry coal before fractionation. The bottom line of the table shows the mass of each fraction obtained from 100 g of dry coal. For every 100 g of original dry coal an additional 100 g of extraneous material was present. Elemental balances and other evidence (]J showed this to be made up almost entirely of phenol chemically combined with the coal material, with traces present of residual solvent associated with the fractions as a result of the coal preparation and fractionation scheme. Note that with fractions A and B no solid residue was obtained. 

When analyses are complete, a fractionation scheme is used to determine organic and inorganic sulphur constituents (Fig. 12.5). 

Initial studies designed to obtain a valid subcellular fractionation scheme for rainbow trout liver illustrated the aryl-hydrocarbon (benzo[a]pyrene] hydroxylase activity separated with glucose-6-phosphatase (35). This observation indicated that the trout hemoprotein P-450-mediated monooxygenation system was located within the endoplasmic reticulum (microsomal fraction). 

The n-paraffin separation process utilizes the conventional Sorbex flow scheme shown in Figure 8.1. There are three main sections of a Sorbex unit depicted (i) adsorbent chambers, (ii) Sorbex rotary valve, (iii) product/desorbent fractionation columns. As indicated earlier, desorbent is typically recycled to the Sorbex adsorbent chambers via fractionation. Figure 8.1 depicts a post-Sorbex fractionation scheme using a light desorbent. This term refers to the boiling point of the... 

Fig. 1.3 Fractionation schemes for extracts from the red alga Gigartina skottsbergii. a The initial classic small molecule isolation scheme and b alternative protein isolation scheme...

The pharmacologic studies indicated that intrinsic pharmacokinetics of 5-FU hinder their ability to reproduce the conditions required for radiosensitization. Indeed, the short half-life of the drug (from hepatic removal) preclude anything other than addictive effects when bolus drug is added to any variety of radiation fractionation scheme. These two sets of requirements together demonstrated that a continuous infusion (in which drug is made present for at least 24 h after each radiation fraction) would be optimal. In summary, 5-FU is a potent radiosensitizer under the following defined circumstances. 

Nishioka, M. G., C. C. Chuang, and B. A. Petersen, Development and Quantitative Evaluation of a Compound Class Fractionation Scheme for Bioassay-Directed Characterization of Ambient Air Particulate Matter, Environ. Ini., 11, 137-146 (1985). 

Isolation-Fractionation Scheme. Figure 1 illustrates the isolation-fractionation scheme devised and evaluated in this study. Step 1 The test solution was first acidified to pH 2 and passed through the XAD-8 column by gravity flow at a rate of 15 bed volumes/h. The last portion of the test solution remaining in the column was displaced from the resin by 1 bed volume of 0.01 N HC1 rinse, which was combined with the original test solution. Step 2 The hydrophobic acid fraction was desorbed with 0.25 bed volumes of 0.1 N NaOH followed by 1.5 bed volumes of OFW. Step 3 The test solution effluent from the XAD-8 (pH 2) was adjusted to pH 10 with 1 N NaOH and recycled through the XAD-8 column at a flow rate of 15 bed volumes/h. Following the sample, 2.5 bed volumes of OFW were used to rinse the XAD-8 column. The rinse was com-... 

An isolation-fractionation scheme for the separation of trace organic solutes from natural and drinking waters has been developed. This process involves the separation of a number of organic solutes into several fractions on the basis of their sorptive characteristics onto different adsorbents under varying pH conditions. The specific adsor-... 

Tentatively Identified Artifact Contaminants from Resin Fractionation Scheme... 

When the samples and resins were handled properly, contaminants introduced throughout the isolation-fractionation scheme were found to be minimal. Therefore, it is felt that the proposed process can be properly scaled up to handle large quantities of water for the preparation of concentrates for biological and chemical characterization. 

Figure 2. Fractionation scheme for an extract of chlorinated water, indicating TA100 mutagenicity of the resulting fractions. ++, mutagenic (p = 0.5-5.0) +, mutagenic (p < 0.5) and —, not significantly different from negative controls (p > 0.05). The slope values were calculated as revertants per liter equivalent of water per milliliter of incubate. (Reproduced with permission from reference 16. Copyright 1986 Water Research...

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