# Common HPLC Calculation Formula

HPLC is a technique used to separate and analyze mixtures of compounds in a liquid phase. It consists of Mobile phase and  Stationary phase. Where, mobile phase used to elute the compounds from the column. and stationary phase interacts with the compounds being separated.

#### A List of HPLC Calculation Formula

Column efficiency (N)

A measure of how well a column separates compounds, calculated as N = 16(tR/w)^2, where w is the peak width at half height and tR is the retention time.

Peak capacity (n)

The maximum number of peaks that can be resolved in a chromatogram, calculated as n = 5.54(N-1), where N is the column efficiency.

Resolution (Rs)

A measure of how well two adjacent peaks are separated, calculated as Rs = 2∆tR/(w1 + w2), where ∆tR is the difference in retention times and w1 and w2 are the peak widths at half height.

Selectivity factor (α)

A measure of how well two compounds are separated, calculated as α = k2/k1, where k is the retention factor for each compound.

Retention factor (k)

A measure of how strongly a compound interacts with the stationary phase relative to the mobile phase, calculated as k = (tR - t0)/t0, where t0 is the time it takes for an unretained compound to pass through the column.

Capacity factor (k')

A measure of how much a compound is retained on the column, calculated as k' = (tR - t0)/t0, where t0 is the time it takes for an unretained compound to pass through the column and tR is the retention time of the compound.