Fixed-Bed Chromatography

Fixed-Bed Chromatography

This chromatographical technique is essentially the same as the method used in laboratory analysis. By having the targeted composite substance absorbed into the adsorbent, the chromatographic process divides the mixed substance into its parts. Now let us suppose that the adsorption affinity of substances A, B, C are as follows, A<B<C.

A column as shown in Fig. 1 is packed with adsorbent, and then filled with liquid desorbent. In this state, a fixed amount of the sample liquid (a mixture of A, C) is fed in at one end of the column. Next, if we continually feed in liquid desorbent, each component of the sample (A and C) will move in the adsorbent layers at the migration rates Ua and Uc, each determined according to their individual adsorption affinity. Thus, if there is difference between the migration Ua and Uc, as component A and component C move through the adsorbent layers they will separate from each other. In this way, by collecting the liquids as they successively drip out of the column, the mixture can be separated into fractions each abundant with one of the component materials.

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Since the types and densities of the desorbents can easily be changed, fixed-bed chromatography can be applied to the separation of many types of useful substances. However, in cases where a more precise separation is required, the fact that the fixed-bed chromatographic process results in a material with a low concentration means that higher costs are entailed in once again raising the material's concentration. Thus, although it is difficult to use this method in cases where the final product is not very expensive, the process is still one which can easily be used to separate many components.

However, there are some additional deficiencies which surface when this method is used on a large scale:

1. The entire adsorbent bed is not efficiently utilized.

2. A large quantity of desorbent is consumed, and the separated components are obtained in a diluted state.

3. In order to obtain a successful separation, a sufficiently large difference in the adsorption affinities of the adsorbates is required.

4. The operation is not continuous.

Due to these deficiencies, there have been many innovative attempts to improve the fixed-bed mode so that it can be used as an industrial device.

This chromatographical technique is essentially the same as the method used in laboratory analysis. By having the targeted composite substance absorbed into the adsorbent, the chromatographic process divides the mixed substance into its parts. Now let us suppose that the adsorption affinity of substances A, B, C are as follows, A<B<C.
A column as shown in Fig. 1 is packed with adsorbent, and then filled with liquid desorbent. In this state, a fixed amount of the sample liquid (a mixture of A, C) is fed in at one end of the column. Next, if we continually feed in liquid desorbent, each component of the sample (A and C) will move in the adsorbent layers at the migration rates Ua and Uc, each determined according to their individual adsorption affinity. Thus, if there is difference between the migration Ua and Uc, as component A and component C move through the adsorbent layers they will separate from each other. In this way, by collecting the liquids as they successively drip out of the column, the mixture can be separated into fractions each abundant with one of the component materials.
	We recommend the use of the following internet browsers: Internet Explorer(ver. 3.02 or above) and Netscape Communicator(ver.4.06 or above).
Since the types and densities of the desorbents can easily be changed, fixed-bed chromatography can be applied to the separation of many types of useful substances. However, in cases where a more precise separation is required, the fact that the fixed-bed chromatographic process results in a material with a low concentration means that higher costs are entailed in once again raising the material's concentration. Thus, although it is difficult to use this method in cases where the final product is not very expensive, the process is still one which can easily be used to separate many components. However, there are some additional deficiencies which surface when this method is used on a large scale: 1. The entire adsorbent bed is not efficiently utilized. 2. A large quantity of desorbent is consumed, and the separated components are obtained in a diluted state. 3. In order to obtain a successful separation, a sufficiently large difference in the adsorption affinities of the adsorbates is required. 4. The operation is not continuous. Due to these deficiencies, there have been many innovative attempts to improve the fixed-bed mode so that it can be used as an industrial device.