Frequently used extractants

Tantalum and niobium processing - liquid - liquid extraction 

TBP is less soluble and less dangerous but is more problematic due to its relatively high density. This can lead to poor stratification, especially during the stripping process. Hence, insufficient separation of the strip solution from the extractant can lead to additional contamination, by phosphorous, of the final products [458, 462]. 

Alcohols with a C8 - C12 chain length, characterized by low solubility in aqueous media, may have a particular commercial potential as perspective extractants for tantalum and niobium hydrometallurgical processing. Particular emphasis has been placed recently on the investigation of tantalum and niobium extraction using octanol (C8H 80) in the forms of 1-octanol and 2-octanol [462, 466 - 473]. 

Alternative Isopropylaceton Phosphoric acid Capiyl alcohol  

Properties Methyl wo-butyl ketone (MIBK) Tributyl phosphate (TBP) 2-octanol 

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Zirconium ores contain 1+3% of hafnium, and the construction requirement demands its contents to be less than a hundredth part of one per cent. Extraction procedures of separating zirconium and hafnium proved to be the best. The most frequently used extraction is by TBF in an inert solvent from nitric acid solutions. 

The so-called solvent extraction method by toluene, o-xylene or carbon disulfide is the most common and frequently used extraction method, in which metallofullerenes and hollow fullerenes are preferentially dissolved in solvents. The so-called Soxhlet extraction (a continuous and hot solvent extraction) or ultrasonic extraction is normally employed to increase the solvent extraction efficiency (Khemani et al., 1992). Insolubles in soot are easily separated from this solution by filtration. However, in many cases, the toluene or CS2 extraction is not sufficient, since nearly half of the metallofullerene still remains in the residual soot even after the extensive CS2 extraction. It has been found that metallofullerenes are further extracted from the residual soot by such solvents as pyridine (Inakuma et al., 1995) and 1,2,4-trichlorobenzene (Yamamoto et al., 1994a,b). The metallofullerenes were found to be concentrated in this pyridine or trichlorobenzene extracted fraction. When necessary, the metallofullerene extracts can be stored in carbon disulfide solution for an extended period of time, up to a year. 

Nowadays, SPE is the most frequently used extraction technique for the extraction and concentration of trace organic analytes from water samples. This technique has been applied to the determination ofphthalates in water samples ° ° as well as in biological fluids. 

In the early 1990s it appeared that supercritical-fluid extraction was going to be the future method of choice for extracting environmental soils and solid samples. SEE showed promising recoveries for many environment analytes and used very little solvent (64). As of 2001, it had not gained the widespread use that was predicted (7). SEE is very similar to the ASE technique described above, except that a supercritical fluid is used for the extraction rather than a solvent. Any pure substance that is above its critical temperature (Tc) and critical pressure (Pc) is defined as a supercritical fluid. The most frequently used extraction fluid is CO2. If CO2 is compressed to a pressure above 72.9 atm and heated to above 31.3°C, it becomes a supercritical fluid and exhibits physical properties between those of a gas and a liquid. Carbon dioxide is used most frequently in SEE as an extraction... 

PCA is a frequently used method which is applied to extract the systematic variance in a data matrix. It helps to obtain an oveiwiew over dominant patterns and major trends in the data. 

The inflammable solvents most frequently used for reaction media, extraction or recrystallisation are diethyl ether, petroleum ether (b.p. 40-60° and higher ranges), carbon disulphide, acetone, methyl and ethyl alcohols, di-Mo-propyl ether, benzene, and toluene. Special precautions must be taken in handling these (and other equivalent) solvents if the danger of Are is to be more or less completely eliminated. It is advisable to have, if possible, a special bench in the laboratory devoted entirely to the recovery or distillation of these solvents no flames are permitted on this bench. 

Clinical Analysis Clinical, pharmaceutical, and forensic labs make frequent use of gas chromatography for the analysis of drugs. Because the sample s matrix is often incompatible with the GC column, analytes generally must be isolated by extraction. Figure 12.25b shows how gas chromatography can be used in monitoring blood alcohol levels. 

Destmction of the aluminum complex with ammonia then permits hydrocarbon extraction of the alkaloid. The alkaloid is subsequently both isolated and used as its tartrate salt. This nonnarcotic dmg, for which tolerance may develop, is frequently used orally with caffeine (16) for treatment of migraine it acts to constrict cerebral blood vessels, thus reducing blood flow to the brain. 

Soybean meal is the most frequently used source of supplemental protein in the United States (5). Cottonseed meal is another important protein supplement. Both meals are by-products from oil extraction of the seeds. Canola meal is derived from rapeseed low in emcic acid [112-86-7] and glucosinolates. Linseed (derived from flax seed), peanut, sunflower, safflower, sesame, coconut, and palm kernel meals are other sources of supplemental protein that are by-products of oil extraction (4). 

The Ts of methacryhc polymers may be regulated by the copolymerization of two or more monomers as illustrated in Figure 1. The approximate T value for the copolymer can be calculated from the weight fraction of each monomer type and the T (in K) of each homopolymer (15). Acrylates with low transition temperatures are frequently used as permanent plasticizers (qv) for methacrylates. Unlike plasticizer additives, once polymerized into the polymer chain, the acrylate cannot migrate, volatilize, or be extracted from the polymer. 

Development of extraction-free photometric procedures for the determination of traces of metals for which hygienic and environmental regulations have been established is an urgent problem. For solution of this problem we used as an organic reagent l-(2- pyridylazo)-naphtol-2 (PAN) which forms intensely coloured complex compounds with many metals and is frequently used for their extraction-photometric determination however these procedures did not find wide application in water analysis due to lack of selectivity and necessity of using organic solvents. 

There are at least four kinds of information available from an Auger spectrum. The simplest and by far most frequently used is qualitative information, indicating which elements are present within the sampling volume of the measurement. Next there is quantitative information, which requires a little more care during acquisition to make it extractable, and a little more effort to extract it, but which tells how much of each of the elements is present. Third, there is chemical information which shows the chemical state in which these elements are present. Last, but by far the least used, there is information on the electronic structure of the material, such as the valance-band density of states that is folded into the line shape of transitions involving valance-band electrons. There are considerations to keep in mind in extracting each of these kinds of information. 

A structure more distantly related to these is amfenac (10). Like most of the others, amfenac, frequently used after tooth extraction, is an antiinflammatory agent by virtue... 

NMR, Raman and IR spectroscopy are most frequently used to investigate the complex structures of fluoride solutions containing tantalum and niobium. Most investigations of such solutions were performed on the liquid-liquid extraction of tantalum and niobium, with the objective of describing the mechanism of the process. These publications will be discussed separately. 

For centuries, the beneficial effects of crude extracts from the ginkgo tree were well known in China and India. In traditional Chinese medicine, a boiled-down extract of ginkgo leaves is inhaled to alleviate asthmatic symptoms, and, in India, ginkgo extracts constitute a key ingredient of Soma, a mystical liquid that is thought to increase life span.5 The Japanese know it as the Itcho tree and they frequently use its edible fruit, the ginkgo nut, in cooking. 

Before leaving ionic liquids it is worth mentioning their potential value in separation processes. Organic solvents are frequently used in multiphase extraction processes and pose the same problems in terms of VOC containment and recovery as they do in syntheses, hence ionic liquids could offer a more benign alternative. Interesting applications along this line which have been studied include separation of spent nuclear fuel from other nuclear waste and extraction of the antibiotic erythromycin-A. 

Depicted in Fig. 2, microemulsion-based liquid liquid extraction (LLE) of biomolecules consists of the contacting of a biomolecule-containing aqueous solution with a surfactant-containing lipophilic phase. Upon contact, some of the water and biomolecules will transfer to the organic phase, depending on the phase equilibrium position, resulting in a biphasic Winsor II system (w/o-ME phase in equilibrium with an excess aqueous phase). Besides serving as a means to solubilize biomolecules in w/o-MEs, LLE has been frequently used to isolate and separate amino acids, peptides and proteins [4, and references therein]. In addition, LLE has recently been employed to isolate vitamins, antibiotics, and nucleotides [6,19,40,77-79]. Industrially relevant applications of LLE are listed in Table 2 [14,15,20,80-90]. 

The most frequently used methods of analyte isolation and concentration for organic compounds involve distillation, extraction auid adsorption techniques. Some typical applications of these techniques and their attendant -advantages and disadvantages for the analysis of trace organic solutes in water are summarized in Table 8.1 [4,26]. These methods will be elaborated on below and in subsequent sections of this chapter. 

Liquid diromatography is frequently used to further fractionate a sample ter solvent extraction on the basis of... 

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