Chromatography Practice Test

Peak sharpness reflects how efficiently a column separates solute molecules, and this efficiency is captured by the plate count. A higher number of theoretical plates means the peak is narrower and less broadened, indicating better separation efficiency. The plate count N is linked to tR and the peak width W (for a Gaussian peak, N ≈ 16 (tR/W)²). Since W increases with peak broadening, increasing broadening lowers N, making N inversely related to how broad the peak becomes. That’s why this parameter best reflects the trade-off between peak width and column efficiency. W is directly the measure of how broad the peak is, so it correlates with broadening itself rather than inversely. Retention time tR tells you when the peak elutes, not how broad it is. The mobile-phase residence time tM isn’t a measure of peak broadening.