The van Deemter equation from reduced parameters and its use in column diagnosis

6 THE VAN DEEMTER EQUATION FROM REDUCED PARAMETERS AND ITS USE IN COLUMN DIAGNOSIS 

The empirical van Deemter equation (see Section 2.2) with dimensionless values is as follows  

A is a function of packing quality (and also of k) and is greater than 2 (up to 5) in poorly packed columns. 5 is a function of the sample diffusion coefficient and is not altered by anything else. C is a function of the packing material, i.e. of its mass-transfer properties. Hence the reason for poor performance in columns with a small number of theoretical plates is more likely to be found if A and C are known. However, A, B and C cannot be calculated at all unless many h v) pairs have been determined with sufficient accuraey, so a qualitative assessment of the h v) curve is much more convenient  

No such details can be given for the H u) curve as its position is a function of particle diameter and diffusion coefficient alone. 

If assessment of the whole h v) curve is too time consuming, even one pair of values can provide a certain amount of information  

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