Two nearly resolving peaks:

The other measure of the efficiency of a column is resolution, R_s. As in other analytical methods, the word resolution is used to express the degree to that adjacent peaks are separated. For chromatography, the definition is,

R_s=(t_R )_B- (t_R )_A/((w_b )_A + (w_b )_B/2)     =    2d/ (w_b )_A + (w_b )_B

here, d is the distance among the peak maxima for two solutes A and B. Figure describes the way in that resolution is calculated. Tangents axe drawn to the inflection points in sequence to determine the widths of the peaks at their bases. Generally, adjacent peaks of equivalent area will have equal the similar peak widths, and (w_b)_A will equivalent (w_b )_B. Thus, Eq. 7.6 is reduced to the following:

R_s = d/w_b                                                                                                                                        

Within Figure, the tangents are touching so d = w_b and R_s = 1.0. The larger the value of resolution, a better the separation complete baseline separation needs a resolution of 1.5.

Figure:  Two nearly resolving peaks illustrating the definition of resolution, Rs