In absence of water the magnitude of the charge–charge interaction is significantly greater.

TLS Online TPP Program

#Id: 2795

#Unit 13. Methods in Biology

The smaller the value of H and the greater the value of N, the more efficient is the column in separating a mixture of analytes.

TLS Online TPP Program

#Id: 2796

#Unit 13. Methods in Biology

The number of theoretical plates in the whole column of length L is equal to L divided by the plate height:

TLS Online TPP Program

#Id: 2797

#Unit 13. Methods in Biology

Relationship between the number of theoretical plates (N) and the shape of the analyte peak.

TLS Online TPP Program

#Id: 2798

#Unit 13. Methods in Biology

The precise relationship between the three factors and plate height is expressed by the van Deemter equation which is

where ux is the flow rate of the eluent and

A, B and C are constants for a particular column and stationary phase relating to multiple paths, longitudinal diffusion and equilibration time respectively

TLS Online TPP Program

#Id: 2799

#Unit 13. Methods in Biology

Example of a van Deemter plot. The plot shows that the optimum flow rate for a given column is the net result of the influence of flow rate on longitudinal diffusion, equilibration time and multiple pathways.

TLS Online TPP Program

#Id: 2800

#Unit 13. Methods in Biology

A chromatogram is a pictorial record of the detector response as a function of elution volume or retention time.