Separation of organic compounds

New silica gels obtained by sol-gel polycondensation of tetra-ethylorthosilicate (TEOS) or related silanes offer largely superior performance in liquid chromatography (LC) separation of organic compounds, a task for which several thousands tons of silica are employed worldwide by industry. LC devices now rank third behind analytical balances and pH meters in number of installed analytical instruments.1... 

Pervaporation has become one of the standard membrane technologies with a large number of realized industrial applications. Pervaporation is used for the dehydration of organic compounds, the separation of organic compounds from aqueous solu-... 

Horvath CG, Lipsky SR. Use of hquid ion exchange chromatography for separation of organic compounds. Nature 211, 748-749, 1966. 

Adsorption chromatography. This chromatographic technique is best known because of its use in the last century as a preparative method of separation. Stationary phases have made a lot of progress since Tswett. who used calcium carbonate or sugar. The separation of organic compounds on a thin layer of silica gel or alumina with solvent as a mobile phase are examples of this type of chromatography. Solutes bond to the stationary phase because of physisorption or chemisorption interactions. The physico-chemical parameter involved is the coefficient of adsorption. 

This technique involves the separation of organic compounds on the basis of their ability to act as ligands towards certain metal ions. The metal ions are bound strongly to an ion-exchange resin such as Chelex 100 which has iminodiacetate groups as the active sites. 

Some examples of separation of organic compounds from mixtures (p-xylenes/m-xylenes, benzene/cyclohexane) were discussed, including separation of organic gases, wastewater, and organic solutions Review (Chinese)... 

Some specific studies were performed for separation of organic compounds from SC CO2 through an asymmetric polyimide membrane. Different solutes were investigated ethanol [24], isooctane [25], and some petroleum components [26]. Results were expressed as separation factor Usoi/co ... 

Membranes having effective pore sizes between 0.001 and 0.01 pm are used in nanofiltration. NF is placed between reverse osmosis and ultrafiltration, and because of that it is sometimes considered as loose reverse osmosis. Typical operating pressures for NF are 0.3-1.4 MPa. The process allows to separate monovalent ions from multivalent ions, which are retained by NF membrane. The process can be used for separation of organic compounds of moderate molecular weight from the solution of monovalent salts. The very well-known application in nuclear industry is boric acid recovery from contaminated cooling water in nuclear reactor. There are some examples of nanofiltration applications and studies done with the aim of implementation in nuclear centers described in literature. Some of them are listed in the Table 30.4. 

Ability of separation of monovalent ions from multivalent ions Separation of organic compounds from monovalent salts... 

Separation of organic compounds capable of com-plexing with transition metal ions through N, S, O, and 7i-electrons in the molecule. The separation mechanism is similar to IMAC. With its high selectivity, the sample concentration can be low, from... 

Argentation chromatography, in which silver is used as a 7T complexing metal on a silica gel support, is usually employed for the separation of organic compounds with electron-donor properties due to the presence of unsaturated groups in the molecule of the analytes (see Table 2). 

Steam distillation. If two liquids are nearly insoluble in each other, neither one lowers the vapor pressure of the other therefore the total vapor pressure of a mixture of these two liquids will be the sum of their vapor pressures. If the mixture is heated, boiling begins when the combined vapor pressure of the two immiscible components equals the pressure of the atmosphere. The vapor and hence the distillate contain both components in the ratio of their vapor pressures. If, for example, at the temperature of the distillation 95 per cent of the vapor pressure is due to component A (of a mixture A and B), then the composition of the distillate will be 95 mole per cent A and 5 mole per cent B. This principle is applied in the separation of organic compounds from a mixture, at temperatures which are far below their boiling point, by distillation with steam. Consider, for example, a mixture of aniline, which boils at 184°, and water. At 100° the vapor pressure of aniline is 45 mm and that of water 760 mm at 98° the vapor pressure of water is 727 mm and that of aniline 40 mm. Therefore the combined vapor pressure of a mixture of water and aniline at 100° is 805 mm, and at 98°, 767 mm. It is evident that near 98° the total vapor pressure will be one atmosphere and the mixture will boil., The distillate will contain water and aniline in the mole ratio of their partial pressure. The process is called steam distillation and is further discussed in Experiment 27 (page 163). 

Endres, H. and Hermann, H. (1963). Preparative and analytical separation of organic compounds by means of chromatography on polyamide. Agnew. Chem. Inst. Ed. Eng. 2, 254-260. 

Silica with bonded fullerene probably can be used for the separation of organic compounds by reversed phase liquid chromatography if the fullerene modifying layer will be stable to hydrolysis. The reaction of fullerenes with amino groups can be used for the modification of capillary columns for the separation of compounds by capillary gas chromatography. 

The use of supported ionic liquid membranes in different fields of application has received growing attention during last decade. One of the most studied applications of SILMs is the selective separation of organic compounds. The first example was reported by Branco et al. [18], who studied the selective transport of 1,4-dioxane,... 

Fig. 2. Separation of organic compounds from water. Conditions 115°C, 60 ml of Hj per minute, column 6 foot X %e inch, ethylvinylbenzene-divinylbenzene polymer. Reproduced from Hollis (HIO) with permission.

Hennion, M.C., J.C. Thieblement, R. Rosset, P. Scribe, J.C. Marty, and A. Saliot. 1983. Rapid semi-preparative class separation of organic compounds from marine lipid extracts by high-performance liquid chromatography and subsequent quantitative analysis by gas chromatography. J. Chromatogr. 280 351-362. 

Cheng, H.F. and Sabatini, D.A. (2007) Separation of organic compounds from surfactant solutions A review. Separation Sci. Technol., 42(3), 453-475. 

For the GC separation of organic compounds (e.g., saturated and unsaturated hydrocarbons, aromatic compounds, alcohols, aldehydes) a new type of stationary phase has been proposed [160—162] crystallohydrates. The melting and decomposition points of the crystallohydrates determine the temperature range in which they can be used. 

For the selective separation of organic compounds, specially prepared metal salt adsorbents (e.g., copper salts) are used, after volatile components have been eluted from them [106—108]. Good separations on these columns were obtained for isomeric ketones for example, heptanone-2, heptanone-3 and heptanone-4 were separated. Delventhal et al. [109] proposed the use of metal-containing polymers for the separation of various amines and thiophene. The advantage of these stationary phases was stated to be their high chemical and thermal stability. Nawrocki et al. [156] studied the application of coordination polymers as adsorbents and LSPs in GC. 

Compared to the competing methods of gas-liquid chromatography (GLC) and liquid-solid chromatography, gas-solid cbrorftatography (GSC) is today of minor importance in the separation of Organic compounds. GSC techniques were in use prior to the introduction of GLC in 1952 [see review of Ref. (7)], but the latter method quickly displaced almost all interest in separations by GSC. Within the past 5 years there has been a widespread renewal of interest in GSC for the separation of organic samples, but the future role of GSC in this area is still not clear. 

Host-guest complexation is now recognized as one of the most important and well-established fields of the modern chemistry [1-24. It deals with various subjects from methane (e.g., [I6a ) to nucleotides (e g., [I6b-19]) and integrates various approaches, both theoretical and experimental. Naturally, it also has a huge variety of practical applications among them, isolation and separation of organic compounds are our primary interest. 

Polymeric-inorganic composites have been developed mainly for the separation of organic compounds through pervaporation (PV) and vapor permeation (VP). However, they can also be advantageously used for such reactions as esterification and condensation. 

On the Use of Ionic Liquid Technology for the Selective Separation of Organic Compounds and Metal Ions... 

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