M/s. Gulf Analytical Supplies FZE have an established presence of nearly a decade in the middle east market and have a dominant presence in the field of separation science comprising mainly of chromatography with more than thousand columns supplied in the Middle East.  With the help of application support and technical support from our principals, we are the pioneers in the field of column chromatography.

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Products / SGE Analytical Science / HPLC Columns

HPLC Columns
Don’t Forget to Choose the Appropriate Pore Size of Your Reversed Phase Column!
What is often ignored by chromatographers is the choice of optimal pore size of the silica for the appropriate application. In liquid chromatography virtually all interactions (and therefore retention) takes place inside the pore system. The exterior surface of common porous silica makes up less than 1 % of the total surface area. In order to use the available interactive surface, the analyte molecule needs unrestricted access to the particle interior. In most chromatographic applications pore diffusion is the time limiting step (the slowest step which therefore governs the overall kinetics). After overcoming the film mass transfer resistance, the solute has to diffuse into the pore system in order to bind to the surface since most of the surface is inside a porous particle (>99 %). For larger molecules such as proteins, pore diffusion becomes a crucial factor.

A number of models have been derived to describe the effect of the pore diameter on the diffusion constant of a solute molecule. These models range from the Fickian diffusion where the diffusion rate is purely concentration driven (large pores – small solute molecules – the mean free path of the Brownian motion is small compared to the pore diameter); to the Knudsen diffusion, where the mean path of the Brownian motion is equal or larger than the pore diameter (collisions with the wall play a major role in the determination of the diffusion rate). An extreme case is the single file diffusion, where the diameter of the solute solute molecule is larger than the radius of the pore. In this case molecules are unable to pass each other. In addition, an estimation for the steric hindrance at the pore entrance and the frictional resistance within the pore system was provided by Renkin.

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