Detector response vs time:

Let us first consider a detector responding to concentration. Ideally, we have the following relationship

R = K₁C

where, R is detector response in millivolts,

K₁ is a constant of proportionality, and

C is a concentration of the solute passing by the detector.

If the detector response is plotted against time t, we get a curve shown in Figure.

Figure:  Detector response vs. time

If the shaded area under curve is A and substituting a value of R as provided in Eq. we get

 Now let us assume a solute zone within the form of a plug in that the element concentration is constant and equivalent to M/V where, M is the total mass of a solute in the plug and V is the plug volume.