Organic mixtures

An improved solvent extraction process, PUREX, utilizes an organic mixture of tributyl phosphate solvent dissolved in a hydrocarbon diluent, typically dodecane. This was used at Savannah River, Georgia, ca 1955 and Hanford, Washington, ca 1956. Waste volumes were reduced by using recoverable nitric acid as the salting agent. A hybrid REDOX/PUREX process was developed in Idaho Falls, Idaho, ca 1956 to reprocess high bum-up, fuUy enriched (97% u) uranium fuel from naval reactors. Other separations processes have been developed. The desirable features are compared in Table 1. 

Chromatography is often used with advantage for the purification of small amounts of complex organic mixtures. Chromatography techniques all rely on the differential distribution of the various components in a mixture between the mobile phase and the stationary phase. The mobile phase can either be a gas or a liquid whereas the stationary phase can either be a solid or a liquid. 

Inghram and Corner showed that the mass spectra of molecules were much simpler using a field ionization source than with an electron bombardment ion source. Mainly parent ions are formed, unlike under electron impact which gives rise to considerable fragmentation. The simplicity of the mass spectra offers obvious applications in analysis of complex organic mixtures and their use is likely to become widespread... 

The open-column technique is commonly applied in the case of crude oils (being the least complex geochemical organic mixtures). MPLC, high-pressure liquid chromatography (HPLC), and PTLC are more often applied to more complex samples, especially those dominated by more polar compounds, such as hydrothermal bitumens or samples showing terrestrial organic matter input, such as extracts or pyroly-sates of coals of various ranks. 

Steam distillation is normally carried out as a semi-batch process whereby the organic mixture is charged into the still and steam is bubbled through continuously, as depicted in Fig. 3.64. 

The SS technique has also proved to be informative for studying intermediate particles in radiolysis of organic mixtures in gaseous and liquid media [20]. 

The use of thermomorphic systems has recently been studied as a way of achieving catalyst separation in homogeneous catalysis. For example, a biphasic hydroformylation catalyst system was developed to take advantage of the unusual solvent characteristics of perfluorocarbons combined with typical organic solvents (4). Fluorous/organic mixtures such as perfiuoromethylcyclohexane... 

In 1998, Miyaura reported a Rh(acac)(CO)2/dppp-catalyzed addition of aryl or alkenylboronic acids to aldehydes in aqueous organic mixtures under an inert atmosphere (Eq. 8.85).216 The use of electron-rich tri(tm-butyl)phosphine as ligand was found to be beneficial for obtaining good yields of the corresponding aldehyde addition products.217... 

Wooley, E. M. Tomkins, J. Hepler, L. G., Ionization constants for very weak organic acids in aqueous solution and apparent ionization constants for water in aqueous organic mixtures, J. Solut. Chem. 1, 341-351 (1972). 

Wu, Z. Rodgers, R. R Marshall, A. G. Two- and three-dimensional van Krevelen diagrams A graphical analysis complementary to the Kendrick mass plot for sorting elemental compositions of complex organic mixtures based on ultrahigh-resolution broadband Fourier transform ion cyclotron resonance mass measurements. Anal. Chem. 2004, 76, 2511-2516. 

It is difficult in practice to use ec reduction as a method of detection in hplc. Oxygen is very easily reduced, and if it is present in the mobile phase it will create a background current thousands of times larger than the current due to the solutes. To prevent this, oxygen would have to be very carefully removed. This can be done, but it certainly is not easy in practice. So most of the ec applications are oxidations. Another important consideration with ec detectors is that the mobile phase used must have fairly high conductance, so they are used with aqueous-organic mixtures containing added salts, or with buffer solutions. 

Exclusion chromatography is also useful in the separation of small molecules from interfering matrices of larger molecules, for example in foods or other samples of biological origin. It can be used as the first step in the sequential analysis of complex unknown organic mixtures, which are first separated on a size basis by exclusion, then the collected fractions can be further separated by normal or reverse phase chromatography, where the separation is based on chemical differences. 

In hplc the mobile phase can be an aqueous-organic mixture, a buffer solution or a mixture of organic solvents, depending on the... 

Under different types of agreements, short- and long-term projects are undertaken in close alignment to customer needs. Joint projects are meant to discover and synthesize new molecular entities designed for specific functions, discovery new and more efficient approaches to the synthesis of target molecules, and characterization of components of complex organic mixtures. 

In this section we will examine examples of organic transformations performed by using microwave energy to heat organic mixtures. In all the examples included in this section, the chemical reagents are dissolved in a solvent that couples effectively with microwaves and generates the heat energy required to promote the transformations. 

On the basis of the knowledge that different polyelectrolytes can stabilize proteins [180], even in water-organic mixtures [181], it was important to check the membraneforming polyelectrolyte itself as a potential stabilizer. Indeed, as was found from spec-trophotometric investigations, Nation stabilizes glucose oxidase suspensions in organic solvents. 

FIGURE 13.7 The remaining activity of alcoholdehydrogenase (O) and glucose oxidase ( , A) after 30 minutes exposing to concentrated ethanol (O), isopropanol (A), and acetonitrile ( ) as a function of water content in water-organic mixture. 

Banerjee, S. (1984) Solubility of organic mixture in water. Environ. Sci. Technol. 18, 587-591. 

Smith [83] classified large sets of hydrocarbon oil infrared spectral data by computer into correlation sets for individual classes of compounds. The correlation sets were then used to determine the class to which an unknown compound belongs from its mass spectral parameters. A correlation set is constructed by use of an ion-source summation, in which a low resolution mass spectrum is expressed as a set of numbers representing the contribution to the total ionisation of each of 14 ion series. The technique is particularly valuable in the examination of results from coupled gas chromatography-mass spectrometry of complex organic mixtures. 

H. Aziz, Y.F. Liew, H.M. Grandin, and Z.D. Popovic, Reduced reflectance cathode for organic light-emitting devices using metal organic mixtures, Appl. Phys. Lett., 83 186-188, 2003. 

The analysis of organosulphur compounds has been greatly facilitated by the flame photometric detector [2], Volatile compounds can be separated by a glass capillary chromatographic column and the effluent split to a flame ionization detector and a flame photometric detector. The flame photometric detector response is proportional to [S2] [3-6]. The selectivity and enhanced sensitivity of the flame photometric detector for sulphur permits quantitation of organosulphur compounds at relatively low concentrations in complex organic mixtures. The flame ionization detector trace allows the organosulphur compounds to be referenced to the more abundant aliphatic and/or polynuclear aromatic hydrocarbons. 

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