Chromatography Calculator

Retention factor (k') is a measure of how long a compound is retained on the column relative to the void time. It's calculated as (tR - t0) / t0, where tR is retention time and t0 is void time. A k' value between 2-10 is generally optimal for good separation.

Theoretical plates (N) can be calculated using N = 16(tR/Wb)², where tR is retention time and Wb is peak width at base. Higher N values indicate better column efficiency and narrower peaks.

Resolution (Rs) values greater than 1.5 indicate baseline separation between peaks. Rs = 1.0 gives about 98% separation, while Rs = 1.5 provides complete baseline separation. Resolution is calculated as Rs = 2(tR2 - tR1)/(W1 + W2).

Plate height (HETP) is calculated as column length divided by theoretical plates (L/N). Longer columns typically provide more plates but also higher plate heights. The goal is to minimize HETP for maximum efficiency.

Selectivity (α) measures the relative retention of two compounds, calculated as k'2/k'1. It indicates how well the stationary phase can distinguish between compounds. Resolution depends on selectivity, efficiency, and retention.

Focus on achieving k' values of 2-10, maximizing theoretical plates, and ensuring Rs > 1.5 for critical separations. Adjust mobile phase composition for selectivity, flow rate for efficiency, and column dimensions for resolution.

Column efficiency is affected by particle size, column packing quality, flow rate, temperature, and mobile phase viscosity. Smaller particles, optimal flow rates, and proper temperature control improve efficiency and reduce plate height.

Linear velocity shows how fast the mobile phase moves through the column. It's calculated from flow rate and column dimensions. Optimal linear velocity balances analysis time with separation quality, typically 1-3 mm/s for most applications.