Extractives examples

Extraction techniques for polymeric matrices can be divided into traditional and new . The traditional techniques include Soxhlet extraction, boiling under reflux, shaking extraction and sonication. All these methods are at atmospheric pressure. When the sample is added to a solvent, which is boiled under reflux (i.e. at the highest possible temperature without applying an external pressure) extractions tend to be much faster than Soxhlet extractions. Examples are the Soxtec ,... 

Principles and Characteristics In boiling under reflux procedures a small amount of ground polymer (typically 3g) is placed in a headspace jar (typically 100 mL) and solvent (typically 30 mL) is added. After sealing, the jar is placed in an oven at a temperature where the solvent slowly refluxes. The solvent is, therefore, at the highest temperature possible without applying an external pressure. Consequently, reflux extractions tend to be much faster than Soxhlet extractions. Examples are Soxtec , Soxtherm , FEXTRA and intermittent extraction. Whilst, in theory, partitioning of the analyte between the polymer and solvent prevents complete extraction, this hardly ever constitutes a problem in practice. As the quantity of solvent is much larger than that of the polymer, and the partition coefficients usually favour the solvent, very low additive levels in the polymer result at equilibrium. Any solvent or solvent mixture can be used. 

An essential step in industrial solvent extraction is the regeneration of the extractant. This can be done in many ways, e.g., by distillation, evaporation, or stripping (back-extraction). While distillation and evaporation do not discriminate between solutes (the diluent is simply removed by heating), stripping, by careful choice of strip solution and conditions, can be made highly selective. Alternatively, aU the solutes can be stripped and then subjected to a selective extraction by changing the extractant examples of both types of process will be found in Chapter 13. The possibilities are many, and it may be worthwhile to explore new paths. 

Schedule 2 is intended for drugs that also have a high potential for abuse and for addiction but do have a currently accepted medical use, albeit often a highly restricted one. These drugs include many opiates that are used medically, as well as certain coca extracts. Examples include fentanyl and methadone (the latter being used medically for maintenance of heroin addicts). 

Extraction example If q = 3, then 4 of the solute remains in phase 1 after one extraction. A second extraction reduces the concentration to 4 of the value after the first extraction =... 

The detector can be used to confirm electronegativity, but there are no good theories linking the structure of practical compounds to electronegativity. In contrast to the ECD, the microcoulomet-ric detector can be made quantitatively specific for chlorine, at the expense of sensitivity. In the food extract example, good procedure would be to rerun the extract on a coulometric detector. 

Diuron from soil Diuron spiked Tama soil was the extraction example used in the six vessel multi-vessel extractor. As is illustrated in Table III, the average recovery for these samples was 97.3% and the relative standard deviation was 6.6%. When these results are compared to those obtained with the classical extraction techniques, equivalent recoveries were achieved. However, the precision associated with the classical extraction was typically 20%. Acceptable recovery ranges in classical residue analysis are from 70 to 125%. Comparing these precisions with those obtained with a one vessel SFE device, the... 

Phenyl Metabolite of NUSTAR from Wheat The phenyl metabolite of NUSTAR was the extraction example used for twelve vessel multivessel extractor. As is illustrated in Table IV, the average recovery for these samples was 91.0%, with a relative standard deviation of 12.4%. Two samples were lost in this extraction example. The loss was attributed to overpressurization of the extraction system. The wheat sample which is ground with dry ice in a blender as a standard sample handling procedure for classical as well as the supercritical fluid extraction, frequently contains small fine particles. These particles can readily block the 0.45 pm frits at the end of the extraction vessel. The advantage of our system, is that the loss of one sample in the series does not interfere with the accurate extraction of the rest. 

The so-called "trapped sites" of classical mobile-site, liquid ion exchanger electrodes belong to a category of compounds known as ion association extractants. Examples are long-chain diesters of phosphoric acid and tricaprylylmethylammonium (Aliquat) ions. The latter cation was studied extensively by Freiser and co-workers (1-3 ) in the design of anion sensors. 

Up until now, most of the published work on the SFE of natural products has been concerned primarily with nonpolar substances such as essential oils, lipids, flavor, and fragrance ingredients. However, recent reports have shown that some polar plant constituents (e.g. flavonoid glycosides, proteins, and steroidal glycosides) can be extracted by SFE as effectively as conventional organic solvent extraction. Examples of SFE applications for natural products are well reviewed in several literature sources [19-22]. 

FIGURE 9.2 Stage diagram for countercurrent multistage liquid-liquid extraction (Example 9.1). 

Acetic-acid extraction examples in this chapter used both isopropyl ether and 1-butanol. Which is a better solvent Why ... 

GC-MS analyses of the extracts obtained after rutheniumtetroxide oxidation revealed either compounds previously described as hydolysis or BBr3 treatment products or novel compounds only occuring in RuCE extracts. Examples for the first group of anthropogenic contaminants are linear alkylbenzenes (LAB) with 11 to 13 carbon side chain length,... 

A food extract, such as a lemon extract, is really not a chemical extraction but consists of the essential oils that are mechanically pressed out of lemon skin and then kept in a 45% solution of alcohol. A drug extract is called a tincture. Tinctures are usually alcohol solutions and are liquid-solid extractions. Examples are the tincture of iodine, oil of wintergreen, oil of clove, and oil of peppermint. Cosmetic extracts such as ambergris, musk, castor, and benzoin, are called essences and are used to make perfumes. 

Figure 4.12 Flow sheet for zirconium-hafnium extraction example.

FIGURE 20.13 McCabe-Thiele diagram extraction (Example 20.3). 

Stage number in rectifying section also mass flow rate of water in extract (Example 20.3), kg/h or Ib/h Critical pressure, bars... 

To obtain fluorescence lifetimes time correlated single photon counting (TCSPC) was used. In TCSPC, the elapsed time is measured between an excitation pulse from a pulsed laser and a detected photon. A histogram of the elapsed times provides a fluorescence decay curve, from which the fluorescence lifetime, Zf, is extracted. Examples of decay curves for bare silica and single R6G molecules on silica taken with a near-field probe are shown in Fig. 11 [21]. 

For many years, in most cases synthetic polyelectrolytes such as PDADMAC or PEI as PC, and PAC, PAMPS, or PSS as PA were used for complex formation. But at present, the application of so-called natural polymers is of growing importance in the field of complex formation. Natural polymers occur in nature and can be extracted. Examples are chitosan as well as polysaccharides such as starch, pectin, or alginate. Natural polymers are used because of their good biodegradability and high biocompatibility in a wide range of applications in industry. They can have cationic charge (chitosan) [137] or can be modified with cationic as well as hydro-phobic units [74]. 

The multiple-extraction example shown here illustrates that several extractions with small volumes is more efficient than a single extraction procedure. This is always true provided the partition coefficient is neither very large nor very small. If the partition coefficient Kp for a substance between two solvents is very large Kp > 100) or very small Kp < 0.01), multiple extractions (using the same total amount of solvent) do not significantly increase the efficiency of the extraction process. ... 

The idea is then to invoke the MSG Method twice, so as to tune the admissibility parameters a and b according to these construction categories. Remember that for admissible examples of arity a + 2b, the last b parameters are constructed from the middle b parameters, while the first a parameters may or may not be used in these constructions. So we first apply the MSG Method on the extracted examples that fall into the first construction category (because the word all allows us to fix a = 0 and b=l), and we then apply it on all the other extracted examples (where a = 2 and b = 0). 

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