Improving Separation by Increasing the Column Efficiency

The peak broadening due to diffusion is related to the square root of L as follows  

If a peak diffuses as a theoretical Gaussian distribution, wh is equal to 4a. One peak width is 4a standard deviation, from Equation 5.4  

The effective number of theoretical plates is the number of usable theoretical plates and is calculated after elimination of the void volume  

If the peak widths of peaks 1 and 2 are assumed to be equal, the following equation is derived from Equation 5.1  

A column having a smaller HETP value is a good column because diffusion inside the column is small, resulting in better separation. The HETP value is given by the Van Deemter equation, which describes the peak broadening of packed columns through which a non-compressible solvent is moving. 

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