Column Efficiency and Height Equivalent of the Theoretical Plate

5 Column Efficiency and Height Equivalent of the Theoretical Plate 

The difference between the two inflection points is thus Aoj = 2Ni. This is the volume of mobile phase, expressed as the number of units of phase volume (v,jj + K. v ), that elutes from the column between the two inflection points, so the actual volume (e.g., in mL, p,L etc.) is  

Equation [3.19] gives the Plate Theory expression for peak width in conventional volume units. To relate this to the experimental chromatogram note that, from Equation [3.12], the retention volume V, (maximum of the peak) is given by V, = N.(v,jj -I-K. vj, so Equation [3.19] becomes  

In practice it is often difficult to locate the inflection points of a real peak, particularly if appreciable noise 

Equation [3.21] is the basis for routine monitoring of the performance (column efficiency) of a chromatographic column. 

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