Classical ion-exchange chromatography

As an example, consider the separation of the creatine kinase isoenzymes, MM, MB, and BB. Mercer has used classical ion-exchange chromatography (DEAE - Sephadex - A50) for the resolution of these three isoenzymes (44) To speed up the separation and ultimately to allow an automated analysis,... 

U Butikofer, D Fuchs, JO Bosset, W Gmur. Automated HPLC-amino acid determination of protein hydrolysates by precolumn derivatization with OPA and FMOC and comparison with classical ion exchange chromatography. Chromatographia 31 441-447, 1991. 

Finally, in 1979, Bidlingmeyer et al. [13,14] introduced a third model which they termed the ion interaction model. It is based on conductivity measurements, the results of which rule out the formation of ion pairs in the mobile phase. This retention model, also used by Pohl [15] to interpret the retention mechanism on a MPIC phase, neither presupposes the formation of ion pairs nor is it based on classical ion-exchange chromatography. 

These hydrophilic macroporous packings for classic ion exchange chromatography of biopolymers, and methods of their application are described in detail in commercial brochures available on request [19,20]. 

SO3H) for cations, is the same in HPLC as in classical ion exchange chromatography. A variety of substrates ranging from cross-linked polystyrene, cross-linked polydextrans, cellulose and silica have been utilised. However, due to the problems of swelling, compressibility and mass transfer encountered with macroreticular polymeric supports and the limited pH stability of silica-based packings, the efficiencies achieved in lE-HPLC applications have been moderate. 

Modern ion chromatography is built on the solid foundation created by extensive work in classical ion-exchange chromatography. Columns containing ion-exchange resins have been used for many years to separate various cations and... 

Gas chromatography (GC) for amino acid analysis is the alternative to HPLC that has found the greatest acceptance. It requires the preseparation derivatization of the amino acids to render them volatile. For this purpose, amino acids are frequently converted into acylated esters. N-Trifluoroacetyl-n-butyl esters and /V-heptafluorobutyrylisobutyl esters are most commonly employed. There have been comparative studies (3,4) that document similar (if not equivalent) analytical results for GC and the classic ion-exchange chromatographic method applied to a variety of food samples. Comparison (5) of GC to the reversed-phase HPLC determination of amino acids (phenylisothiocyanate derivatized) also shows excellent agreement. 

Ion-Exchange Chromatography. Ion exchange is perhaps the most classic and popular type of chromatography used in biochemistry. It relies on the differential electrostatic affinities of molecules car-... 

Oddly, IPC was also performed on a classical ion exchange colnmn to separate 17 anionic, neutral, and cationic arsenic species in a single chromatographic run, thanks to a multiplicity of retention modes on this packing material [39], Ion pairing proved also valuable in size exclusion chromatography of sulfonated lignins [40],... 

Classical LLPC using aqueous-aqueous polymer systems based on Albertsson s [9] PEG-dextran system has provided a versatile tool for the separation of proteins and nucleic acids, thus increasing the arsenal of biopolymer purification methods currently dominated by gel filtration, ion-exchange chromatography, and affinity chromatography RPC. The technique operates... 

The classical model of selectivity12 in ion-exchange chromatography is based upon stoichiometric exchange for example, the competition of Na+ and Li+ for sites on a cation-exchanger (R ) ... 

The modulator (in NPLC, a strong, polar solvent, or in IXC, a buffer) or the organic modifier (in RPLC, methanol, acetonitrile, or THE) may affect the retention of the components of the sample in different possible ways. In the most classical case, such as in ion-exchange chromatography or in normal phase HPLC, the... 

Stationary phases for ion chromatography have a lower exchange capacity than the ones used for classical ion-exchange separations as described in Chapter 12. Therefore, the ionic strength of the eluent can be low and 1 mM solutions are not uncommon. Diluted mobile phases have low conductivity which facilitates detection. However, even with mobile phases of low electrolyte concentration, the background conductivity is too high to allow detection without special techniques. Two principles... 

Modern liquid chromatography can be carried out in any of the classical modes, e.g., liquid-solid adsorption chromatography, liquid-liquid partition chromatography, reversed-phase chromatography, ion-exchange chromatography, and gel-permeation (size exclusion) chromatography. 

This chapter summarizes the majority of the literature on ion exchange chromatography in biochemistry over the five years preceding 1981. Occasionally some important older works are cited (especially reviews or monographs). It can be seen from the literature that even today many authors are satisfied with the use of older, classically proven, but time consuming, low pressure separation methods and develop them further. On the contrary, at the same time a broad shift to modern trends can be observed, which is represented by numerous applications of the rapid medium and high pressure liquid chromatography in various fields of biochemistry. Therefore both approaches must be discussed here. 

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