Fast chromatography types

Another approach in GC is that of using more power in the separation by doing GCxGC. In this approach, a second column is used with a different type of stationary phase than the primary stationary phase, and fast chromatography using TOF-MS as the detector is carried out [39]. This technique uses only TOF-MS as the detector since it has the most sensitivity for fast-eluting peaks. The method has been applied to complicated matrix analysis. 

More recently, fused core columns from Supelco and core-shell columns from Phenomenex and Agilent have gained much interest in the field of fast chromatography. The particles used in these columns are made of a sub-1.2 to -2 pim solid core and a 0.35-0.5 p.m porous outer shell, with an overall particle size below 3 p-m, providing a compromise between high efficiency and modest operating pressures. Consequently, one can run these columns on conventional HPLC instruments to obtain very rapid separations. In UHPLC, however, smaller internal diameter columns can be used to reduce solvent consumption. Users can refer to several papers for advantages and applications of these two types of columns (22, 50-52). 

The ELP expression system was compared to the conventional oligohistidme fusion, which is traditionally applied for purification by immobilized metal affinity chromatography (IMAC). Both techniques were shown to have a similar yield of the recombinant protein. The temperature-triggered approach offers a fast and inexpensive nonchromatographic separation with the possibility for larger scale purification. Although the ELP expression system may not be applicable to all types of recombinant proteins, numerous examples have already been shown [40]. 

Cabrera K. Lubda D. Eggenweiler H. Minakuchi H. Nakanishi K. A new monolithic-type HPLC column for fast separations. Journal of High Resolution Chromatography, 2000, 23, 93-99. 

Partition chromatography as described in this section may be applied to two major types of problems (1) identification of unknown samples and (2) isolation of the components of a mixture. The first application is, by far, the more widely used. Paper chromatography and TLC require only a minute sample size, the analysis is fast and inexpensive, and detection is straightforward. Unknown samples are applied to a plate along with appropriate standards, and the chromatogram is developed as a single experiment. In this way any changes in experimental conditions (temperature, humidity, etc.) affect standards and unknowns to the same extent. It is then possible to compare the Rf values directly. 

Analytical separation and spectroscopic techniques normally used for petroleum crudes and residues were modified and used to characterize coal liquids, tar sands bitumens, and shale oils. These techniques include solvent extraction, adsorption, ion-exchange, and metal complexing chromatography to provide discrete fractions. The fractions are characterized by various physical and spectroscopic methods such as GLC, MS, NMR, etc. The methods are relatively fast, require only a few grams of sample, provide compound type fractions for detailed characterization, and provide comparative compositional profiles for natural and synthetic fuels. Additional analytical methods are needed in some areas. 

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