Column chromatography definition

It must be stressed that the value obtained in this way for mixtures of carotenoids is only an approximation. For more definitive analysis column chromatography (unit F2.3) should be used. 

In order to equate Eq. (5) with Eq. (1), two different definitions of H, one has to assume that L = tR. Thus, in column chromatography, the interpretation of L is that it represents the retention time, and the definition of [Pg.35]

The principles of paper chromatography are similar to those of column chromatography discussed in Chapters 14 to 18. The main difference is that a piece of paper is used for the inert phase. The solution to be examined is deposited as a small spot on the paper. The mobile phase is allowed to move over the spot in a definite direction, and the substances are separated by their differences in solubility in the moving solvent and the stationary phase, which generally is considered to be the water normally present in paper. Isaac Asimov, the well-known science fiction writer. 

Practical implementation of two-dimensional separation is very easy in TLC. By definition, all the components of the sample are subjected to both separation dimensions, and components separated in the first dimension remain resolved in the second dimension. When a two-dimensional separation fulfills these requirements, it is considered comprehensive. From the practical point of view, multidimensional separations are much more difficult to implement in column chromatography. To perform the 2D separation in space, i.e., in a manner analogous to... 

Partial purification of the lividomycin-inactivating enzyme was attempted by Mitsuhashi and coworkers, who briefly described their discovery that the enzyme obtained by fractionation with ammonium sulfate and column chromatography on Sephadex G-lOO inactivates lividomycins A and B, but not kanamycin A, indicating involvement of two different enzymes in the phosphorylation of lividomycin and kanamycin. However, it was definitely proved by H. Umezawa and coworkers that kanamycin-neomycin phosphate transferase I phosphorylates the 5"-hydroxyl group of lividomycins. The observation by Mitsuhashi and coworkers was probably occasioned by instability of the enzyme and the higher activity of the enzyme in phosphorylating lividomycins than in phosphorylating kanamycin A. 

Isomers of i-B,OH-Bio were separated by fractional crystallization and column chromatography. H, Si, and MALDI-TOF MS and single crystal XRD definitely confirmed the stracture of each isomer. 

The need for a more definitive identification of HPLC eluates than that provided by retention times alone has been discussed previously, as have the incompatibilities between the operating characteristics of liquid chromatography and mass spectrometry. The combination of the two techniques was originally achieved by the physical isolation of fractions as they eluted from an HPLC column, followed by the removal of the mobile phase, usually by evaporation, and transfer of the analyte(s) into the mass spectrometer by using an appropriate probe. 

By definition, the e]q>erlmentally determined average mobile phase velocity Is equal to the ratio of the column length to the retention time of an unretalned solute. The value obtained will depend on the ability of the unretalned solute to probe the pore volume. In liquid chromatography, a value for the Interstitial velocity can be obtained by using an unretalned solute that Is excluded from the pore volume for the measurement (section 4.4.4). The Interstitial velocity Is probably more fundamentally significant than the chromatographic velocity in liquid chromatography (39). 

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