Chromatography Resolution Calculator

Rs of 1.5 or above, which leaves under 0.3% overlap between adjacent peaks. Rs of 1.0 still leaves roughly 2%, which is why the working threshold is 1.5.

Twice the difference in retention times divided by the sum of the two peak widths at base. Using widths at half height instead requires a different constant, so check which convention a value follows.

Retention time minus void time, divided by void time — how long a compound spends in the stationary phase relative to the mobile phase. Values between 2 and 10 are generally the useful working range.

Because it enters the resolution equation linearly while plate count enters under a square root. Doubling column length quadruples analysis time for only about 41% more resolution; a small change in mobile phase composition can do much more.

A measure of column efficiency borrowed from distillation, counting the notional equilibration steps a column performs. Higher plate counts mean narrower peaks and better separation.

Height equivalent to a theoretical plate — column length divided by plate count. Smaller is better, and the van Deemter equation describes how it varies with flow rate through a minimum.

Either, but the constant changes. Width at base uses N = 16(tR/w)²; width at half height uses N = 5.54(tR/w½)². Half-height is easier to measure on a tailing peak, which is why software usually reports it.

Usually secondary interactions — residual silanols on a silica column interacting with basic analytes is the classic case. Column overload, a void at the column inlet and extra-column dead volume all produce it too. Tailing inflates apparent width and understates the plate count.

HETP = A + B/u + Cu, splitting plate height into eddy diffusion, longitudinal diffusion and mass-transfer resistance. Because B falls and C rises with flow rate, the curve has a minimum — the flow at which the column is most efficient.

Smaller particles reduce the A and C terms, flattening the van Deemter curve so efficiency holds at much higher flow rates. The same separation runs several times faster, at the cost of backpressure that needs purpose-built pumps.

By changing selectivity, since it enters the resolution equation linearly while plate count enters under a square root. A small change in mobile phase composition, pH or temperature often beats doubling the column length, which returns only 41% for twice the run time.

Between 0.9 and 1.5 for most methods; pharmacopoeial methods often specify 2.0 as the limit. Outside that range, integration becomes unreliable and the plate count no longer means what the equation assumes.