Separation methods conventional chromatography

Capillary electrophoresis employing chiral selectors has been shown to be a useful analytical method to separate enantiomers. Conventionally, instrumental chiral separations have been achieved by gas chromatography and by high performance liquid chromatography.127 In recent years, there has been considerable activity in the separation and characterization of racemic pharmaceuticals by high performance capillary electrophoresis, with particular interest paid to using this technique in modem pharmaceutical analytical laboratories.128 130 The most frequently used chiral selectors in CE are cyclodextrins, crown ethers, chiral surfactants, bile acids, and protein-filled... 

Karlsson and Novotny [12] introduced the concept of nanoliquid chromatography in 1988. The authors reported that the separation efficiency of slurry packed liquid chromatography microcolumns (44 xm, id) was very high. Since then, many advance have been reported in this modality of chromatography and it has been used as a complementary and/or competitive separation method to conventional chromatography. Unfortunately, to date no correct and specific definition of this technique has been proposed, probably due to the use of varied column sizes (10 to 140 xm). Some definitions of nanoliquid chromatography are found in the literature based on column diameter and mobile... 

Because of polydisperse nature of HS, the importance of separation methods increased as the science evolved. Various separation methods were widely used for conventional fractionation and characterization of components based on differences in component solubility, charge, molecular weight, and/or size, polarity, hydropho-bicity, and so on (Janos, 2003). More recent research focused on advanced molecular-level analyses of humic mixtures (Hertkorn and Schmitt-Kopplin, 2007), in which a combination of separation techniques, mostly, chromatography, or capillary electrophoresis) were coupled with high-resolution instrumental analysis [e.g., mass spectrometry (MS) or nuclear magnetic resonance (NMR) spectroscopy]. Several examples appeared in the literature, including those that used size exclusion chro-... 

From the great variety of methods for the determination of protein binding three separation methods, equilibrium dialysis (ED), ultrafiltration (UF), and ultracentrifugation (UC) and a non-conventional method with the binding to immobilized proteins has been chosen. The first methods are undoubtedly the most widely used because of their simplicity and general applicability to many different systems. Other methods e.g. size exclusion chromatography, capillary electrophoresis, or spectroscopic methods have been not described. Oravcova et al. (1996) gives a comprehensive review and comparison for these applications. 

To illustrate the rapidity of HPLC, particularly in comparison with the more conventional techniques, the same sample was separated by conventional ion-exchange chromatography. Figure 5.10 compares the two procedures. These data show that where 14 hours was required for the traditional method, only about 45 minutes is required with HPLC. Therefore, the total time needed to carry out this purification, not counting the time for the enzyme assay, could be as short as 3 to 4 hours. If necessary, the chromatography step could be completely automated. Finally, since each run will use only a fraction of the total volume of the starting material, the entire procedure will be economical. 

Gradient elution chromatography is a separation method that exploits the effect of the fluid phase composition on the retention behavior of the feed components. It is widely used, especially for analytical separations in the areas of the life sciences, in biochemistry, and in the biotechnologies e.g., separation of complex mixtures of proteins or peptides), hi its conventional implementations, SMB units are operated under isocratic conditions. The composition of the fluid phase, e.g., the organic modifier concentration, the pH, or the buffer concentration remain constant in all the sections of the SMB unit. However, it has recently been shown that SMB units can also be operated under solvent gradient mode (SG-SMB). Then, the feed and desorbent streams introduced have a different composition. The fluid phase composition is different in each section. It is chosen independently, in order to... 

In conventional chromatography, gel-permeation is one of the commonest methods for separating proteins. The technique is based on the partial exclusion of large molecules from a porous matrix. In HPLC, gel-permeation has not been so widely used for the separation of proteins, which may be due to the lack of gel-permeation supports compatible with aqueous mobile phases and resistant to high operating pressures. However, suitable supports have recently been developed (e.g., TSK gels) and it is anticipated that this method for the high-resolution separation of proteins will expand in the foreseeable future (F8, H6). 

Conventional chromatography is a slow method of analysis. The retention times are often longer than an hour when separating components of a complex mixture. To reduce these times, influence can be brought to bear upon several parameters. The most obvious requires the use of a shorter column and so as not to lose efficiency, the diameter of the capillary column should be reduced (cf. expression... 

The other new trend in ion exchajige column separation methods is ampholyte displacement chromatography (ADC) and chromatofocusing (CF). Leaback and Robinson [43] — who first published the ADC method — used conventional ion exchangers for the separation of proteins, and carrier ampholytes for the elution. Using this approach the authors succeeded in resolution of isoenzymes unresolvable... 

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