Resolution

It is often important to be able to separate a large number of compounds. A visual inspection of the chromatogram (Fig. 31.8) will usually indicate whether the separation is appropriate. It is desirable that the valley between adjoining peaks returns to the base line and resolution is a quantitative measure of the separation. The influence of k', α and N on resolution, R, is shown in the following expression:

⇒ Equation [31.6]	R =	√N	×	k'	×	α − 1
		4		k' + 1		α

Three conditions must be satisfied in order to achieve some degree of resolution:

1. Peaks have to be retained on the column (k' > 0).
2. Peaks have to be separated from each other (α > 1).
3. The column must develop some minimum value of N.

Fig. 31.8 A multicomponent chromatogram. Separation of many compounds, some well resolved, e.g. peaks at 12-13 mins, and others that are not, e.g. peaks at 24-25 mins.

Fig.31.9 Influence of k', α and N on resolution.