Separation on ion-exchange columns

In summary we underline the fact that as far as urine analysis is concerned, and this is also true for blood, the most satisfactory results published so far are those obtained with Moore and Stein s 1954 procedure (see (b) Dowex 50-X4 columns) whereas the two latest improvements in technique open the way to much wider investigation in this field of biochemical and medical research. The technique is also applicable for the determination of a single amino acid, adequate shortcuts and simplifications in the procedure being introduced accordingly. As examples, we shall mention that appropriate rapid operations have been described for the separation on ion exchange columns and subsequent determination of (3-alanine (C20), (3-aminoisobutyric acid (E5) or y-aminobutyric acid (W1). Similar adjustments may also be made for other amino acids, such as the basic amino acids, for instance, with Moore and Stein s 1954 procedure (M15). 

In Table V are collected the most important peptides isolated by Heyns et al. (1951), Schroeder et al. (1953), 1954), and Kroner et al. (1953, 1955), following acid hydrolysis of steer hide collagen and gelatin. The peptide fractions were separated on ion exchange columns, and individual peptides resolved on celite, followed by sequence studies carried out by the methods of Sanger. 

Separation of As(lll) from As(V) in ground waters by means of anion exchanger in acetate form has been proposed [27,27a]. Arsenic(V) is retained in the anion exchanger bed, whereas As(III) passes through. As(V), P(V), and Si were also separated on ion exchange columns [28]. 

By exploiting the differences in stability of various complexes of Cu and other metals, it is possible to achieve separations on ion-exchange columns. Owing to the different stability of the chloride complexes, copper has been separated from Ga, Fe(III), and Zn by ion-exchange on anion- or cation-exchange resins. The anionic chloride copper(I) complex (in the presence of ascorbic acid) has been retained on anion-exchanger Dowex 1 from 0.1 M HCl medium copper was then eluted with 1 M nitric acid [6]. 

Figure 8.6 Amino acid separation on ion-exchange column, with automatic recording of the effluent composition.

The extent to which the ions compete with B for the charged sites (X) will determine their retention. In general, this type of chromatography may be used to separate ionic species, such as organic acids or bases, which can be ionized under certain pH conditions. Besides the reaction with ionic sites on the stationary phase, retention may also be affected by the partitioning of solutes between the mobile and stationary phases, as in reversed-phase chromatography. Thus, even nonionized solutes may be retained on ion-exchange columns. 

Oligosaccharides and related materials can be separated by a partition mechanism on ion-exchange columns where water/alcohol mobile... 

Sakamoto, T., Yamamoto, S., Yahata, K., and Kondo, T., Studies on bile pigments. VI. Separation of natural bilirubins on ion exchange columns. Igaku Kenkyu 27, 121-123 (1957). 

For small neutral organic compounds, reversed-phase chromatography usually provides much better efficiency than lEC. However, a mixed-mode separation mechanism on ion-exchange columns can offer a unique selectivity for the separation of some biopolymers such as peptides or proteins [73). 

Since the chloride complex of Ni is much weaker than those of Co, Cu, Zn, Fe(IlI), and certain other metals, it is possible to separate nickel from these metals on ion-exchange columns [7]. When a solution in 8-9 M HCl is passed through a strongly basic anion-exchanger, nickel alone is eluted. Nickel has been separated from other metals using aqueous acetone or aqueous methanol solutions [8]. 

Reports of such separations achieved on ion-exchange columns are too numerous to be listed here, but some typical examples are as follows. 

Rare earths can be separated from each other on ion-exchange columns, as illustrated in Pig. 3.2. Once separation conditions have been defined, the method can be simplified for purifying one radionuclide such as " Pm from interfering rare earth radionuclides. 

Ion-exchange chromatography separates compounds on the basis of their molecular charges. Compounds capable of ionization, particularly zwitterionic compounds, separate well on ion-exchange column. The separation proceeds because ions of opposite charge are retained to different extents. The resolution is influenced by ... 

The kinds of chemical substances that can be separated by the various types of chromatography are very numerous. Within the field of chromatography alone many methods are applicable to such separations, for example, adsorption, thin-layer, and partition chromatographies (on paper and on ion-exchange columns), and gel filtration. Morris and Morris (1964) have discussed the various techniques and their applications. 

The macro separation of stable isotopes on ion exchange columns. J. Chim. Phys. (France) 60, 89. with D.E. Hegland and S. Legvold, Magnetization and electrical resistivity of terbium single crystals. Phys. Rev, 131, 158-162,... 

Several studies were devoted to the construction of automated equipment for rapid and remote-controlled operation. In 1966, Samsahl (1966) published a paper about the development of an automated system that was based on ion-exchange column separation. 

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