 Chromatographic resolution

Chromatographic resolution measures the separation of two peaks relative to their widths. With chromatographic retention times $t_{R2}>t_{R1}$ and baseline widths $w_{b1},w_{b2}$, its conventional definition isThe numerator and denominator have the same units, so $R_s$ is dimensionless. A large time difference does not by itself imply good separation if both peaks are correspondingly broad.^[ref]

For an original example, peaks at $4.0$ and $4.6$ minutes, each $0.40$ minutes wide at the base, have $R_s=2(0.6)/(0.8)=1.5$. If their widths increase to $0.60$ minutes while their peak times stay fixed, $R_s=1$. Measuring only the peak centers would miss the deterioration.

Simply rescaling the time axis cannot change chromatographic resolution. If all times and widths in the first example double, then $R_s=2(1.2)/(1.6)=1.5$ again. This is a statement about a rescaled trace, not a claim that changing the flow of a real column leaves its separation physics unchanged.

The peak-width convention must be stated. Half-height widths are smaller than baseline widths and cannot be substituted into the same formula without the corresponding conversion. Peak asymmetry, overlapping components and unequal signal strengths can also make a single reported $R_s$ an incomplete account of whether a particular quantitative measurement is reliable.