Flash Chromatography – An Introduction
Flash chromatography is also known as “medium pressure chromatography”. This form of chromatography works by air pressure driving the mixture, which is to be separated down the vertical glass column. This type of chromatography is ideal for separations that need to take place in a fast paced manner.
How Flash Chromatography Works
In the traditional column chromatography, the mixture that has to be separated is placed on the top of the column using a stationary phase like Silica Gel. Then it moves through a mixture of solvents with some help from gravity. The different components will be separated at various levels. While the separation and purification is done in a proper manner, the biggest disadvantage of using column chromatography is its slow rate. This is where the advantages of using flash chromatography come into the forefront. Under flash chromatography, the solvent is forced down the vertical column with the help of positive air pressure.
When air pressure is applied, the rate at which the solvent is flowing increases, thus bringing down to a large extent, the amount of time required to separate any given mixture. If one is to use flash chromatography then the separation process can be completed right under 10-15 minutes. The time saved while purifying the sample is the main reason why companies opt for the flash chromatography. You get the same result like column chromatography with flash chromatography, but in lesser time. So one can save time and most importantly, money.
Across the world, flash chromatography is fast replacing the slow moving gravity-dependent chromatography. If one is to look closely at how flash chromatography functions, you can see that this form of chromatography makes use of slightly smaller Silica Gel molecules. This would mostly be in the range of 250-400 mesh. Another main point about flash chromatography is that because of the restricted movement of the solvent caused by the small gel particles, pressurized gas is generally used to drive the solvent through the stationary or solid phase column.
Silica Gel in Flash Chromatography
As mentioned earlier, Silica Gel is one of the desiccants used as the stationary phase in the flash chromatography process. It is widely used because of two most important characterisitics – its numerous interconnected pores and large surface area. These two features help the Silica Gel stationary phase absorb the different components of the mixture in a fast and timely manner.
The amount of silica gel adsorbents being used in flash chromatography depends on the Rf difference of the compound, which are up for separation and on the amount of sample used. For easier separations, ratios closer to 30:1 are highly effective. While for difficult separations, more silica gel adsorbents are used by companies. However, by using more silica gel, one also extends the length of time required for the chromatography process to be completed. Silica Gel for Flash chromatography is available with Silica Gel 70-230 Mesh suppliers like Sorbead India.