Chromatographic Resolution

The goal of chromatography is to separate a mixture into a series of chromatographic peaks, each representing a single component of the mixture. The resolution between two chromatographic peaks, RAB, is a quantitative measure of their separation, and is defined as

RAB = (tr,Btr,A)/{½(wB + wA)} = 2Δtr/(wB + wA)

where B is the later eluting of the two solutes. As shown here, the separation of two chromatographic peaks improves with an increase in RAB. If the areas under the two peaks are identical—as is the case in this illustration—then a resolution of 1.50 corresponds to an overlap of only 0.13% for the two elution profiles. Because resolution is a quantitative measure of a separation’s success, it is a useful way to determine if a change in experimental conditions leads to a better separation.


We can improve the resolution between two solutes by increasing Δtr or by decreasing wA and wB. The illustration below shows two method for improving chromatographic resolution: (a) original chromatogram; (b) chromatogram after decreasing wA and wB by 4×; (c) chromatogram after increasing Δtr by 2×.


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