Separation method

Separation of alkali metals by cation exchange using 2 mM HNO3 as eluent and a Waters IC Pak C column. The peaks are in the negative direction because indirect conductivity detection is used (p.S = micro-Siemens). (From Ref. 5 with permission.) 

Schematic illustration of the equilibria existing between a solute cation (M ), ethylenediamine (en), and an added ligand (H2L) at the surface of a cation exchanger, (a) Eluent contains only the ligand, (b) Eluent contains both ligand and ethylenediamine. 

Ion interaction chromatography (IIC) (also commonly referred to as ion pair chromatography or mobile phase ion chromatography) involves the use of lipophilic stationary phases (such 

Separation of metal ions when complexing agents are used as eluent components (AU = absorbance units), (a) A Nucleosil SA-10 column was used with 0.5 M tartrate at pH 2.76 as eluent. Detection by postcolumn reaction. (From Ref. 8.) (b) A TSKIC Cation SW column was used with 3.S mM citric acid-10.0 mM ethylenediamine at pH 2.8 as eluent. Detection by conductivity. (From Ref. 9.) 

One widely accepted mechanism for IlC [10] proposes that a dynamic equilibrium is established between HR in the eluent and HR adsorbed onto the stationary phase as follows  

Several methods have been used to separate the daughter nuclide Tc from parent Mo, the three most common methods are column chromatography, solvent extraction, and sublimation (Boyd 1982 Richards 1982). 

The Mo/ Tc generator used in nuclear medicine is based on the chromatographic separation of Tc-pertechnetate. 

All the separation methods used to classify physical and chemical properties of crude oil can be classified into the following classes  

The preparation of sample for both methods is done in the same way as was shown for column chromatography. However, both methods differ in the solvents used for desorption. In the case of the desorption method, the solvents used should have a stronger absorption ability than the compounds in the sample mixtures. Solvents used for analyzing crude oil and its products include alcohols, ketones, ethers, chlorine-containing solvents, benzene, toluene and so on. It is possible to 

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Large amounts of solvents with lower adsorption ability than the compounds of the sample mixture are used in the elution method. Pentane, hexane, heptane and petrol ether are frequently used by crude oil chemists as solvents for elution adsorptive analysis. 

The third method is molecular distillation. This is distillation under very low pressure. Usually the pressure for this analysis varies from 0.133 Pa up to 0.013 Pa. The heavy fractions of crude oil can be separated with this method. The name molecular distillation is derived from the fact that the vapor pressure of the high molecular compounds depends almost linearly on the boiling point of these compounds under vacuum. It means that the separations by this method proceeds according to the molecular weight of the compounds in the sample. The quality of the separation depends on the evaporation velocity of the compounds in sample mixture. 

In this chapter we discuss the important separation methods based on chromatography, electrophoresis and centrifugation. We consider first the physical principles underlying each method and then their application in preparative and analytical work. Since these are core experimental techniques in biochemistry and molecular biology, they are discussed in depth so that they can be used without having to consult additional sources information. 

Biochemical experiments often require the use of homogeneous materials, which have to be purified from undesired compounds. Various separation techniques have been developed for purification purposes, and most are being further developed to improve their performance. Separation techniques are also used analytically to provide information about the composition of mixtures and how these change in the course of a reaction. 

All separation procedures rely on some element of differential transport the separation may be based on differences in phase equilibria, as in chromatography, or on the kinetics of transport, as in electrophoresis and centrifugation. Precipitation procedures, filtration and dialysis are also members of the broad dass of separation methods these have been discussed in an earlier chapter (Sect. 3.4). The transport processes involved in separating components are often opposed by dispersion processes such as diffusion and convection, which have to be minimised to achieve the best separation results. 

Although the removal of interfering substances is an important application of separation methods, this chapter is more concerned with the use of these procedures to isolate, identify or quantify a particular substance or group of substances in the presence of other very similar substances. The quantitation of one amino acid in the presence of other amino acids is only one example of such an analytical problem. 

Tungstic acid Sodium tungstate 10 g 1 , sulphuric acid 0.05 mol 1 1 

Zinc hydroxide Zinc sulphate 10 g 1 1, sodium hydroxide 0.05 mol l-1 

Copper tungstate Cupric sulphate 5.0 g l-1, sodium tungstate 2.5 g l-1 

The selection of a separation method is based on the identification of a suitable characteristic property, whose variation should be important for the component(s) to be separated. Table 3.2 presents characteristic properties for gas separations. A first group of methods relies on physical properties, such as boiling point, relative volatility, solubility, etc., which generates separation techniques such as condensation, distillation, physical absorption, etc. The second category exploits the reactivity of some functional groups, as in chemical absorption, catalytic oxidation, catalytic hydrogenation and chemical treatment. 

Ann Westman-Brinkmalm, Jerzy Silberring, and Gunnar Brinkmalm 

Mass Spectrometry. Edited by Ekman, Silberring, Westman-Brinkmalm, and Kraj Copyright 2009 John Wiley Sons, Inc. 

Centrifugation of UF Large pilot plants operating and commercial plants under construction in England and Holland large plant to be built in United States 

Thermal diffusion of UF Small amount of slightly enriched UF produced in United States in 1945 process abandoned 

Electromagnetic separation of UCI4 Used in United States in 1945 for flrst large-scale production of highly enriched U process abandoned in 1946 

Separation nozzle process Process demonstrated on large pilot-plant scale at Karlsruhe, Germany semiconunerdal plant being built in Brazil 

UCOR process Process demonstrated in pilot plant at Valindaba, Union of South Africa commercial plant under consideration 

Name Type Functional group Bead sizes (mesh) % cross-linking Exchange capacity g (dry resin) Form supplied Working pH range  

Deacidite Strong base CHji Rj 14-52, 52-100 2-3, 3-5, 4.0 mmol OH cr 1-14 R = alkyl 

Amberlite Strong base CHji Rj 100-200 8 3.8mmol OH cr 0-12 R = alkyl 

Amberlite Weak base -CH2l R2 100-200 5.0 mmol OH OH 0-9 R = alkyl 

In chromatography the solutions used are mostly dilute, hence the elution technique is much employed and it frequently gives highly satisfactory separations. In addition, all the other methods described in Chapter 1 have been used, although frontal analysis is not often encountered. 

Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary 

As a rule of thumb, GC is used for the separation of volatile compounds. Thus, it is useful for determination of low-molecular-weight compounds (below 500 Da) but cannot be used for large, highly polar or thermally labile compounds. Implementation of GC is simple and routine. GC is mostly coupled with flame ionization detection (FID), electron capture detection (BCD), or mass spectrometry (MS). 

HPLC is used for nonvolatile compounds and is well suited for the analysis of low- and high-molecular weight compounds such as peptides and proteins. HPLC is mostly coupled with ultraviolet visible (UV-VIS) wavelength spectroscopy or mass spectrometric detection. 

Electrophoretic techniques are used for nonvolatile compounds, which are permanently or temporarily charged, such as proteins or organic salts. Electrophoretic techniques have an increasing importance in biomedical fields, such as proteomics. 

Chromatography is a collective name for methods that separate compounds based on their interaction with a mobile phase (in which the sample is dissolved or mixed) and a stationary phase. For instance, the strength of interaction between an apolar compound and an apolar stationary phase is strong thus, the compound will 

Si02 (acid washed) CHCI3 MeOH H2O = 64 36 8 glycosides (11) 

Column chromatography has been employed frequently, using either silica or alumina stationary phases, for isolation of individual anthraquinones. Eluents used for column chromatography usually consist of a series of solvents of increasing polarity. Examples of such separations are found in references (41, 47,119). 

Until now there has only been one report on the use of reversed-phase liquid chromatography (LC) for the isolation of anthraquinones from rubiaceous plants. Demagos and co-workers (44) used reversed-phase liquid chromatography for the separation of anthraquinone glycosides from Morinda lucida heartwood. For the separation of anthraquinone glycosides reversed-phase high performance (HP) LC seems 

A new separation technique which has been applied successfully to the isolation of anthraquinones is droplet countercurrent chromatography (DCCC). Thus Inoue and co-workers have used DCCC for the isolation of anthraquinones (70, 72). For the solvent systems used see Table 6. 

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If waste streams can be recycled directly, this is clearly the simplest method for reducing waste. Most often, though, additional separation is required or a different separation method is needed to reduce waste. 

Gas phase chromatography is a separation method in which the molecules are split between a stationary phase, a heavy solvent, and a mobile gas phase called the carrier gas. The separation takes place in a column containing the heavy solvent which can have the following forms ... 

Finally, micellar systems are useful in separation methods. Micelles may bind heavy-metal ions, or, through solubilization, organic impurities. Ultrafiltration, chromatography, or solvent extraction may then be used to separate out such contaminants [220-222]. 

Knowles P J and Meath W J 1987 A separable method for the calculation of dispersion and induction... 

A separation method in which a mixture passes through a bed of porous particles, with smaller particles taking longer to pass through the bed due to their ability to move into the porous structure. 

A pseudo-separation method in which a species is prevented from participating in a chemical reaction by binding it with a masking agent in an unreactive complex. 

Miller, J. M. Separation Methods in Chemical Analysis, Wiley-lnterscience NewYork, 1975. 

SI units stands for Systeme International d Unites. These are the internationally agreed on units for measurements, (p. 12) size-exclusion chromatography a separation method in which a mixture passes through a bed of porous particles, with smaller particles taking longer to pass through the bed due to their ability to move into the porous structure, (p. 206)... 

Liquid chromatography is a separation method that is often applied to nonvolatile, thermally labile materials such as peptides, and, if their mass spectra are required after the separation step, then a mild method of ionization is needed. Since FAB/LSIMS is mild and works with a liquid matrix, it is not surprising that attempts were made to utilize this ionization source as both an inlet... 

Capillary Electrophoresis. Capillary electrophoresis (ce) or capillary 2one electrophoresis (c2e), a relatively recent addition to the arsenal of analytical techniques (20,21), has also been demonstrated as a powerful chiral separation method. Its high resolution capabiUty and lower sample loading relative to hplc makes it ideal for the separation of minute amounts of components in complex biological mixtures (22,23). 

The procedure is technically feasible, but high recovery of unconverted raw materials is required for the route to be practical. Its development depends on the improvement of catalysts and separation methods and on the avaHabiUty of low cost acetic acid and formaldehyde. Both raw materials are dependent on ample supply of low cost methanol. 

Thorium, uranium, and plutonium are well known for their role as the basic fuels (or sources of fuel) for the release of nuclear energy (5). The importance of the remainder of the actinide group Hes at present, for the most part, in the realm of pure research, but a number of practical appHcations are also known (6). The actinides present a storage-life problem in nuclear waste disposal and consideration is being given to separation methods for their recovery prior to disposal (see Waste treati nt, hazardous waste Nuclear reactors, waste managet nt). 

The wastes from uranium and plutonium processing of the reactor fuel usually contain the neptunium. Precipitation, solvent extraction, ion exchange, and volatihty procedures (see Diffusion separation methods) can be used to isolate and purify the neptunium. 

The choice of separation method to be appHed to a particular system depends largely on the phase relations that can be developed by using various separative agents. Adsorption is usually considered to be a more complex operation than is the use of selective solvents in Hquid—Hquid extraction (see Extraction, liquid-liquid), extractive distillation, or azeotropic distillation (see Distillation, azeotropic and extractive). Consequentiy, adsorption is employed when it achieves higher selectivities than those obtained with solvents. 

Biopolymer Extraction. Research interests involving new techniques for separation of biochemicals from fermentation broth and cell culture media have increased as biotechnology has grown. Most separation methods are limited to small-scale appHcations but recendy solvent extraction has been studied as a potential technique for continuous and large-scale production and the use of two-phase aqueous systems has received increasing attention (259). A range of enzymes have favorable partition properties in a system based on a PGE—dextran—salt solution (97) ... 

Many challenging industrial and military applications utilize polychlorotriduoroethylene [9002-83-9] (PCTFE) where, ia addition to thermal and chemical resistance, other unique properties are requited ia a thermoplastic polymer. Such has been the destiny of the polymer siace PCTFE was initially synthesized and disclosed ia 1937 (1). The synthesis and characterization of this high molecular weight thermoplastic were researched and utilized duting the Manhattan Project (2). The unique comhination of chemical iaertness, radiation resistance, low vapor permeabiUty, electrical iasulation properties, and thermal stabiUty of this polymer filled an urgent need for a thermoplastic material for use ia the gaseous UF diffusion process for the separation of uranium isotopes (see Diffusion separation methods). 

Different combinations of stable xenon isotopes have been sealed into each of the fuel elements in fission reactors as tags so that should one of the elements later develop a leak, it could be identified by analyzing the xenon isotope pattern in the reactor s cover gas (4). Historically, the sensitive helium mass spectrometer devices for leak detection were developed as a cmcial part of building the gas-diffusion plant for uranium isotope separation at Oak Ridge, Tennessee (129), and heHum leak detection equipment is stiU an essential tool ia auclear technology (see Diffusion separation methods). 

Size reduction (qv) or comminution is the first and very important step in the processing of most minerals (2,6,10,20—24). It also involves large expenditures for heavy equipment, energy, operation, and maintenance. Size reduction is necessary because the value minerals are intimately associated with gangue and need to be Hberated, and/or because most minerals processing/separation methods require the ore mass to be of certain size and/or shape. Size reduction is also required in the case of quarry products to produce material of controlled particle size (see Size measurement of particles). In some instances, hberation of valuables or impurities from the ore matrix is achieved without any apparent size reduction. Scmbbers and attritors used in the industrial minerals plants, eg, phosphate, mtile, glass sands, or clay, ate examples. 

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