Separation/purification methods literature

The literature of alkaloids can conveniently be divided into five sections, dealing with (1) the occurrence and distribution of these substances in plants (2) biogenesis, or the methods by which alkaloids are produced in the course of plant metabolism (3) analysis, ranging from the commercial and industrial estimation of particular alkaloids to the separation, purification and description of the individual components of the natural mixture of alkaloids, which normally occurs in plants (4) determination of structure and (5) pharmacological action. 

It is fruitless to attempt detailed study of a phenomenon whose products are not well identified. It is unfortunately frequently noted in the literature, especially in cases of column chromatography, that fractions are only identified as to the chemical operations which brought them to light. Fractions are identified, for example, only by the solvent used. Speculations as to the composition of the radioactive solutes in such solutions can seldom be really reliable, and the presence of an unexpected radioactive species is in such cases undetectable. It is also important in reading the literature to watch out for cases in which the chemical yields of the carriers have not been measured. Extensive decomposition can often occur on silica gel and alumina columns, especially when photosensitive or moisture sensitive compounds are used. For these reasons much of the information now existing in the literature must be regarded as only exploratory, awaiting the development of better analytical methods for separation, purification, identification and determination of the products —known or expected. 

Introduction.—This Report covers the literature published up to approximately the end of September, 1981. Few new carotenoid structures have been reported. The main advances in carotenoid chemistry have been in the stereospecific synthesis of carotenoids with chiral end-groups. Current interest in the possible use of retinoids in cancer chemotherapy has prompted the preparation of a considerable number of retinoic acid analogues. There has been no major new development in the use of physical methods but h.p.l.c. becomes more and more the method of choice for carotenoid separation, purification, and assay, and the increasing number of papers on resonance Raman spectroscopy emphasizes the potential value of this technique in the carotenoid field. 

In the following section, methods for the fabrication and deposition of Pd-based and zeolite MMs are discussed, as well as applications in (de) hydrogenation, SR, WGS, partial oxidation (POx) reactions and fine chemical synthesis. The research on Pd-based MMRs for hydrogen separation, purification and production (by dehydrogenation, SR and WGS reactions) has been selected as a case study, as significant research and, therefore, much information can be found in the literature on this field. 

It was reported that III could be separated from IV by selective hydrolysis of IV (10), but these results were later disputed (12). Indeed, in our hands purification of III by selective hydrolysis of IV to isophorone using the literature method (10) failed. There was no observed change In the product mixture. 

This procedure is based upon a study 1 of the method outlined in the patent literature.2 The procedure is a general one and may be used for the condensation of succinic anhydride with naphthalene and with the mono- and dimethylnaphthalenes, although in no other case are the purification and separation of isomers so easily accomplished. In this particular type of condensation, as well as in certain other types of Friedel-Crafts reactions, nitrobenzene is far superior to the solvents which are more frequently employed. This is partly because of its great solvent power and partly because it forms a molecular compound with aluminum chloride, and so decreases the activity of the catalyst in promoting side reactions. 

Much of the early literature of polonium describes methods for separating it from these mixtures many of these have subsequently been adapted to the separation of milligram amounts of polonium from irradiated bismuth and to its purification. The methods range from a simple chemical separation of the element with a tellurium carrier to its electrodeposition on to a more noble metal or its spontaneous electrochemical replacement on the surface of a less noble metal. 

In Table IV is presented a brief review of the literature relating to surface phenomena. In recent years much interest has been shown in the adsorption of hydrocarbons upon solids. No effort has been made to include references to analytical methods based upon selective adsorption. This process is often employed in the purification of hydrocarbons and in some cases is superior to fractionation. The work of Lewis and Gilliland (45-47) reviews the status of the techniques and data relating to the adsorption of petroleum upon solid surfaces. The increasing importance of such techniques is evidenced by the recent development of commercial processes (5, 80) for the separation of hydrocarbons based on adsorption. 

Isoelectric focusing is a mature separation technique that has a place in any laboratory doing work with proteins. The analysis of a protein is not complete without a determination of its isoelectric point and all protein databases have at least estimates of the pis of the represented proteins. Proteins thought to be pure by other methods are often found to be mixtures of several proteins when analyzed by IEF. Isomeric forms of the same protein that are revealed by IEF are valuable indicators of mutations or differences in posttranslational modifications. IEF plays a crucial role in 2-D PAGE and preparative IEF allows for high-purity fractionations of unparalleled resolution. A simple keyword search of literature databases shows that about 500 journal articles are written per year referring to IEF. This amply attests to the value of IEF as a tool for protein analysis and purification. 

Based upon the use of nonionic surfactant systems and their cloud point phase separation behavior, several simple, practical, and efficient extraction methods have been proposed for the separation, concentration, and/or purification of a variety of substances including metal ions, proteins, and organic substances (429-441. 443.444). The use of nonionic micelles in this regard was first described and pioneered by Watanabe and co-workers who applied the approach to the separation and enrichment of metal ions (as metal chelates) (429-435). That is, metal ions in solution were converted to sparingly water soluble metal chelates which were then solubilized by addition of nonionic surfactant micelles subsequent to separation by the cloud point technique. Table XVII summarizes data available in the literature demonstrating the potential of the method for the separation of metal ions. As can be seen, factors of up to forty have been reported for the concentration effect of the separated metals. 

A wide range of techniques is available for the separation and purification of oligonucleotides after the removal of protecting groups. Obviously, chemical synthesis is not the only source of such compounds, and those derived by purely enzymic syntheses, or after isolation from biological sources, have been examined in similar ways. The literature is correspondingly extensive, and only those methods routinely used after a chemical synthesis will be discussed in detail here. 

It is the ability of hplc to accomplish separations completely and rapidly that led to its original application to problems in the life sciences, particularly those related to purification. An analysis of the literature revealed that this technique was used primarily for the purification of small molecules, macromolecules such as peptides and proteins, and more recently antibodies. This application to purification has all but dominated the use of the method, and there has been a plethora of books, symposia, and conferences on the use of hplc for these purposes. However, it was only a matter of time before others began to look beyond and to explore the possibilities that result from the capacity to make separations quickly and efficiently. 

For many years salting-out by high concentrations of ammoniiun sulfate has been one of the classical methods of protein separation. There is very little literature on the theoretical basis of the method, particularly as applied to the isolation of enzymes, where it has mainly been used quite empirically. The underlying assumption in most cases seems to have been that the different proteins are precipitated at different fixed ammonium sulfate concentrations, provided the pH and temperature are fixed. For example one may commonly read in instructions for the piuification of an enzyme that the enzyme is precipitated at 65% saturation with ammonium sulfate or that the fraction precipitating between 0.62 and 0.68 saturation should be taken. It is, however, a fairly common experience that when one repeats a published method the enzyme fails to precipitate within the limits given. Furthermore, where the purification of a protein involves more than one salt-fractionation stage, the limits are usually found to be different for the different stages. 

Many other RPC methods were used in separation and purification of HA fragments and oligomers including post-column derivatization. Detailed description of such methods can be found in the literature [269],... 

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