Column Chromatography makes easier the Separation of Compounds

Column Chromatography is basically a term used for the separation of compounds from a substance. This procedure proves to be very useful when the compounds are available in the substance in very small amount and hence it becomes very difficult to distinguish them from other. This method is also used when those small amount of mixtures present in the compounds have almost same physical or chemical properties. Chromatography is said to be the best and the most convenient method for separation. The method to be adopted in the separation process in chromatography depends on the distribution of components in a mixture during the fixed or stationary and the mobile or moving phase. The stationary phase is said to be the column of absorbent, which can be a paper or a thin layer of any type of absorber on a glass plate or any other thing through which the mobile phase can pass on.

The mobile phase can be of liquid or gas. When the stationary phase of a solid takes place in a column it is said to be column chromatography. Column chromatography is said to be one of the best and the most useful method of separation and purification of any solid or liquid substance. It is also said as a solid liquid method of separation where the solid is said to be the stationary phase and liquid is said to be the mobile phase. Column chromatography works on the objective based on the differential absorption of substance based on the capacity of the absorbent. Some of the common absorbents used in column chromatography are calcium carbonate, magnesia, starch, alumina, silica and many more. One the contrary the solvent is selected according to the nature of solvent as well as the absorbent.

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Aluminium Oxide Chromatography

Generally, chromatography is separated in to two categories. It is depending on the solvents flows down to the column. If solvent granted to the flow down in the column by gravity, at that time it is called gravity column chromatography. If the column pressured down the column by positive air pressure, at that time it is called flash chromatography. Many type of chromatography like column chromatography, affinity column chromatography, aluminium oxide chromatography, silica chromatography, adsorbents chromatography, molecular chromatography, preparative chromatography, stationery phase chromatography, large scale chromatography, etc. in all type of chromatography silica gel powder is use to separation of mixture in components. This is use in research and development laboratories, pharmaceutical companies and chemical industries.

In column chromatography, there are two type of adsorbents silica and aluminium oxide powder is used in organic chemistry. All these adsorbents having different particle grade-mesh size as displaying number on container label as silica gel 60, 30-70, 60-120, 60-200, 70-230, 100-200, 200-400, 230-400, 400-800. All particle size affects how to solvent flows down though the column. Smaller (finer) particle size is use in flash chromatography and larger (coarser) particle size is use in gravity chromatography. For example, 70-230 mesh use in gravity columns and 230-400 mesh use in flash columns.

Aluminium oxide is used in typically in column chromatography because it is quite delicate to the amount of water which is bound to alumina. In that water level is more which is bound to it and bind organic compounds. In the analysis of column chromatography, thin layer chromatography is the best technic to isolate compounds from the mixture. Usually, the isolated compounds are colorless. In chromatography the "G" stands for Gypsum and suggests calcium sulfate hemihydrate, a sophisticated gypsum has been included in adsorbents ingredients. The "F" indicates the existence of a short wave UV indicator that is fluorescent at 254 nm. Thin layer chromatography having Z grades sizes using silica gel powder. The grade size like silica gel for TLC GF 254 for making glass plates, silica gel G and H for TLC, in which silica gel G offer with binder and silica gel H offer without binder process. Silica gel gf254 is a homogeneous, white and fine powder of an average practical size about 15 µm that is containing around 1.5% fluorescent indicator and 15% calcium sulphate having maximum intensity at 254 nm.

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Various Chromatography Methods

In organic chemistry, columnchromatography adsorbent is the best purification and separation technique of desired compounds from a mixture. Column chromatography used under two techniques like stationery phase and mobile phase. In which stationery phase is a solid adsorbent, to place in vertical column while as in mobile phase is a liquid, is add from the top and solvent flows down through the column by gravity or by the air pressure. The stability is required to maintain between the liquid flowing down though the column and adsorbents. Because in the mixture, there are different components having different interactions with the mobile phase and stationery phase.

There are four types of methods used in silica gel column chromatography. That is analytical chromatography which is used to analyze that how much percentage of mixture is to be purified. This is a very fast and cost effective method for separation. Another is preparative chromatography, which is used to optimize the opportunities of the process and also improves the process of separation. Next is process chromatography where the separation is taken up to a biologics level and separation of proteins, viruses, hormones and anti-bodies is now possible. The last is gravity chromatography which is said to be the manual process. The mixture is allowed to move around by gravitational force.

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Chromatography Techniques

Chromatography is said to be a technique which is used to separate components within any substance. It is basically a biological term with also helps to calculate the chemical composition of any substance. This separation process consists of two phases that is mobile and stationary phase. The basic working is done on the stationary phase when adsorption is done and then the mobile phase is passed into it. This is the procedure which helps in the separation of the constituent mixtures. It is separated on the basis of its absorption rate and solubility. Chromatography is of two types - absorption chromatography and partition chromatography. Absorption chromatography is also divided into column chromatography and thin layer chromatography. Partition chromatography is also divided in to two types. They are paper and gas chromatography.

Among all the methods, people mostly prefer column chromatography as it is the most convenient one and mostly used for the separation of mixed organic substances. In case of silica gel column chromatography, it is available in many types of requires sizes – 60-120 mesh, 30-200 mesh, 70-230 mesh, 100-200 mesh and many more. It is usually used for the purifying the organic compounds like steroids, alkaloid and pharmaceutical work as well.  

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