The goal of chromatography is to separate a sample into a series of chromato- graphic peaks, each representing a single component of the sample. Resolution is a quantitative measure of the degree of separation between two chromatographic peaks, A and B, and is defined as
As shown in Figure 12.8, the degree of separation between two chromatographic peaks improves with an increase in R. For two peaks of equal size, a resolution of 1.5 corresponds to an overlap in area of only 0.13%. Because resolution is a quanti- tative measure of a separation’s success, it provides a useful way to determine if a change in experimental conditions leads to a better separation.
From equation 12.1 it is clear that resolution may be improved either by in- creasing ∆tr or by decreasing wA or wB (Figure 12.9). We can increase ∆tr by en- hancing the interaction of the solutes with the column or by increasing the col- umn’s selectivity for one of the solutes. Peak width is a kinetic effect associated with the solute’s movement within and between the mobile phase and stationary phase. The effect is governed by several factors that are collectively called column effi- ciency. Each of these factors is considered in more detail in the following sections.