Plate Theory and Extensions - Quantitative Analysis from Retention Measurements > Page 48

                             (42)

where (XAB) is the concentration of solutes (A) and (B) in the composite peak,
(XA) is the initial concentration of solute (A),
(XB) is the initial concentration of solute (B),
(n(A)) is the column efficiency for solute (A),
(n(B)) is the column efficiency for solute (B),
(vA) is the volume of mobile phase passed through the column in plate volume of solute (A),
and (vB) is the volume of mobile phase passed through the column in plate volumes of solute (B).

Rearranging (multiplying the top and bottom of the exponent by (nA) and taking (nA2) inside the brackets),

                          (43)

Equation (43) gives the sum of the two peaks and thus produces produce a single envelope. As long as the retention times can be measured precisely, the data can be used to determine the composition of a mixture of two substances that, although having finite retention differences, are eluted as a single peak. This will be possible, if the standard deviation of the measured retention time is small compared with the retention time difference between the two solutes.