Plate Theory and Extensions - Resolving Power of a Column > Page 58

Resolving Power of a Column

For two solutes to be resolved their peaks must be moved apart and maintained sufficiently narrow to be eluted as discrete peaks. The criterion for the separation of two peaks (usually termed the resolution)  is defined as the ratio of the distance between the peak maxima to half the peak width (s) at the points of inflection. The separation of a pair of solutes  2s, 3s, 4s, 5s and 6s apart are shown in Figure 16. For baseline resolution, the peak maxima should be separated by 6s but for most analyses (especially where peak height measurements are employed) a separation of 4s is usually quite satisfactory. Even employing peak area measurements, a separation of 4s will usually provide adequate accuracy particularly if computer data acquisition and processing is employed.

Figure 16. The Separation of Solutes Pairs by 2s, 3s, 4s, 5s and 6s

A resolution of 4s will be assumed when dealing with resolution or column design. The effect of increasing the resolution criteria can easily be accommodated if found necessary.