Extractive separations

The physical process of Hquid—Hquid extraction separates a dissolved component from its solvent by transfer to a second solvent, immiscible with the first but having a higher affinity for the transferred component. The latter is sometimes called the consolute component. Liquid—Hquid extraction can purify a consolute component with respect to dissolved components which are not soluble in the second solvent, and often the extract solution contains a higher concentration of the consolute component than the initial solution. In the process of fractional extraction, two or more consolute components can be extracted and also separated if these have different distribution ratios between the two solvents. 

Minerals and Metals. HCl is consumed in many mining operations for ore treatment, extraction, separation, purification, and water treatment (see Mineral recovery and processing). Significant quantities are also used in the recovery ofmolybdenum (see Molybdenum and molybdenum alloys) and gold (see Gold and gold compounds). This market consumed about 36 thousand metric tons in 1993. 

Several N-substituted pyrroHdinones eg, ethyl, hydroxyethyl and cyclohexyl, are used primarily in specialized solvent appHcations where their particular physical properties are advantageous. For example, mixtures of l-cyclohexyl-2-pyrroHdinone and water exhibit two phases at temperatures above 50°C below that temperature they are miscible in aH proportions. This phenomenon can be used to facHitate some extractive separations. Mixtures of 1-alkyl-pyrroHdinones that are derived from coconut and taHow amines can be used at lower cost in certain appHcations where they may be used instead of the pure l-dodecyl-2-pyrroHdinone and l-octadecyl-2-pyrroHdinone. 

M-iscellaneousFxtractions. Additional extractive separations using sulfolane involve (/) mercaptans and sulfides from sour petroleum (45) (2) /-butylstyrene from /-butylethjlbenzene (46) (J) mixtures of close boiling chlorosHanes (47) and (4) aromatics from kerosene (48—50), naphtha (49,51—53), and aviation turbine fuel (54). 

The leached solids must be separated from the extract by settling and decantation or by external filters, centrifuges, or thickeners, all of which are treated elsewhere in Sec. 18. The difficulty of solids-extract separation and the fact that a batch stirred tank provides only a single equilibrium stage are its major disadvantages. 

Application of rotating coiled columns has become attractive for preparative-scale separations of various substances from different samples (natural products, food and environmental samples) due to advantages over traditional liquid-liquid extraction methods and other chromatographic techniques. The studies mainly made during the last fifteen years have shown that using rotating coiled columns is also promising for analytical chemistry, particularly for the extraction, separation and pre-concentration of substances to be determined (analytes) before their on-line or off-line analysis by different determination techniques. 

Ionic associates (lA) of polyoxometalates (POMs) with threephenylmethane dyes remain as perspective analytical forms for the determination of some nonmetals including P(V), As(V) and Si(IV). Several reasons hinder to the improvement of analytical characteristics of these reactions. Separation of dye excess and its lA with reagent are most important Procedure for extractive separation is often timeconsuming, complex and does not allow complete separation from reagent excess. 

These washings are extracted separately in order to minimize formation of solid lead(Il) sulfate. 

Corticotropin [92307-52-3] polypeptide Mr -4697. Extract separated by ion-exchange on CM-cellulose, desalted, evapd and lyophilised. Then run on gel filtration (Sephadex G-50) [Lande et al. Biochemical Preparations 13 45 1971 Esch et al. Biochem Biophys Res Commun 122 899 1984],... 

Lube oil extraction plants often use phenol as solvent. Phenol is used because of its solvent power with a wide range of feed stocks and its ease of recovery. Phenol preferentially dissolves aromatic-type hydrocarbons from the feed stock and improves its oxidation stability and to some extent its color. Phenol extraction can be used over the entire viscosity range of lube distillates and deasphalted oils. The phenol solvent extraction separation is primarily by molecular type or composition. In order to accomplish a separation by solvent extraction, it is necessary that two liquid phases be present. In phenol solvent extraction of lubricating oils these two phases are an oil-rich phase and a phenol-rich phase. Tne oil-rich phase or raffinate solution consists of the "treated" oil from which undesirable naphthenic and aromatic components have been removed plus some dissolved phenol. The phenol-rich phase or extract solution consists mainly of the bulk of the phenol plus the undesirable components removed from the oil feed. The oil materials remaining... 

Cupferron (ammonium salt of N-nitroso-A -phenylhydroxylamine). The reagent is used in cold aqueous solution (about 6 per cent). Metal cupferrates are soluble in diethyl ether and in chloroform, and so the reagent finds wide application in solvent-extraction separation schemes. Thus Fe(III), Ti, and Cu may be extracted from 1.2 M HC1 solution by chloroform numerous other elements may be extracted largely in acidic solution. 

Many antibiotics have excellent solubihty in oiganic solvents and they are water immiscible. A multistage extraction separates the aqueous phase from the organic phase. Extraction can provide concentrated and purified products. 

Conventional UV/VIS spectrophotometer (manual measurements from strip-chart recorder traces and calculations on the basis of fitted polynomials the extraction/separation step remains). 

Quantitative TLC (an additional internal standard would be provided the extraction/separation step could be dropped). 

Sample solution instability or incomplete extraction/separation would show up if several aliquots from the same sample work-up were put in a series of vials that would be run in sequence that would cover at least the duration of the longest sequence that could be accommodated on the autosample/instrument configuration. For example, if an individual chromatogram is acquired for 5.5 minutes, postrun reequilibration and injection take another 2.75 minutes, and 10 repeat injections are performed for each sample vial in the autosampler, then at least 15 60/(5.5 -I- 2.75)/10 = 11 vials would have to be prepared for a 5 P.M. to 8 A.M. (=15 hour) overnight run. If there is any appreciable trend, then the method will have to be modified or the allowable standing time limited. 

This comparative study pointed out molecular close packing as a key parameter responsible for the thermal stability of proteins in films. In the case of BR, this close packing is reached due to the nature of the sample, while LB organization seems to be a more general procedure, for the same goal can be reached for practically any type of protein sample. The last statement was even confirmed by the comparison of the thermal behavior of extracted separated BR in self-assembled and LB films. It was found that BR in LB films is more stable for this kind of sample. The results will be reported in detail elsewhere. 

Dodson et al. ° have also studied in detail the effect of added bromide on the exchange reaction using precipitation and extraction separations and ° T1 and ° T1 as indicators. The variation in the rate of exchange was found to be governed by the law... 

Tewes et al., using both precipitation and extraction separation techniques, observed essentially complete exchange within the separation time (1 min) during an isotopic study ( V) of this exchange. The media ranged from 0.3 M perchloric acid to 7 M hydrochloric acid reactant concentrations were 10 M. 

The exchange reaction between Np(VI) and Np(V) has been investigated using the isotopic method ( Np) and an extraction separation (Np(VI) with tri-butylphosphate or thenoyltrifluoroacetone in toluene) Cohen et al. have found, for the exchange in perchlorate media, a rate law... 

The choice of the method of analysis depends on the question to address. Spectrophotometry is sufficient for total curcuminoid content determination in a turmeric extract. Separation techniques coupled to mass spectrometry detection and MALDl-TOF are highly sensitive techniques that are more adapted to the identification of metabolites in biological fluids such as urine or plasma. ... 

Because of their very complex chemical structures and heterogeneity, melanins are difficult to extract, separate, and characterize from tissues. Eumelanins are insoluble in water and organic solvents. They can be extracted from tissues with strong chemicals that are capable of removing lipids, proteins, and other tissue components but also lead to the formation of degradation products. Enzymatic procedures were developed for the isolation of eumelanins from mammalian hair and irises. The first step is sequential digestion with protease, proteinase K, and papaine in the presence... 

In order to obtain reliable results, three steps are involved in the analysis sampling and sample preparation carotenoid extraction, separation, identification. 

Relevant Methods for Extracting, Separating, and Identifying Synthetic Colorants... 

In the drying of compound intermediates of refractory and reactive metals, particular attention is given to the environment and to the materials so that the compound does not pick up impurities during the process. A good example is the drying of zirconium hydroxide. After the solvent extraction separation from hafnium, which co-occurs with zirconium in the mineral zircon, the zirconium values are precipitated as zirconium hydroxide. The hydroxide is dried first at 250 °C for 12 h in air in stainless steel trays and then at 850 °C on the silicon carbide hearth of a muffle furnace. 

Sekine K, Imai T, Kasai A. 1987. Liquid-liquid extraction separation and sequential determination of plutonium and americium in environmental samples by alpha-spectrometry. Talanta 34(6) 567-570. 

Table 5.9 summarises the main features of FTIR spectroscopy as applied to extracts (separated or not). Since many additives have quite different absorbance profiles FTIR is an excellent tool for recognition. Qualitative identification is relatively straightforward for the different classes of additives. Library searching entails a sequential, point-by-point, statistical correlation analysis of the unknown spectrum with each of the spectra in the library. Fully automated analysis of... 

Like gas absorption, liquid-liquid extraction separates a homogeneous mixture by the addition of another phase - in this case, an immiscible liquid. Liquid-liquid extraction carries out separation by contacting a liquid feed with another immiscible liquid. The equipment used for liquid-liquid extraction is the same as that used for the liquid-liquid reactions illustrated in Figure 7.4. The separation occurs as a result of components in the feed distributing themselves differently between the two liquid phases. The liquid with which the feed is contacted is known as the solvent. The solvent extracts solute from the feed. The solvent-rich stream obtained from the separation is known as the extract and the residual feed from which the solute has been extracted is known as the raffinate. 

The identification and structural characterization of biological materials, obtained for example from plants, was traditionally carried out via the classical sequence involving extraction, separation, isolation and characterization, a sequence which requires large amounts of substance and a great deal of time. Industrial problems, for example the search for small amounts of contaminants in industrial products or in waste water, also require intensive analytical studies. 

Jayachandran, J. Dhadke, P. M. Solvent extraction separation of cobalt(II) with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A). Chem. Anal. 1999, 44, 157-165. 

Gandhi, M. N. Deorkar, N. V. Khopkar, S. M. Solvent extraction separation of cobalt(II) from nickel and other metals with Cyanex-272. Talanta 1993, 40, 1535-1539. 

---