How to calculate key data in HPLC - INTERNAL ONLY
Date: 24-JUNE-2016 Last Updated: 20-OCTOBER-2025
Sample Formulae for Chromatography
Efficiency (Theoretical Plates):
N = 5.54 ( tR / w1/2 ) 2
5.54 is a constant when using the "Half Height" method. tR is the retention time of the peak and w1/2 is the width at half height.
Capacity Factor (k'):
k' = (tR — t0) / t0
t0 = (the volume of the mobile phase inside the column) / (Flow Rate)
tR = Band Retention Time
Selectivity (Alpha Value):
a = k2 / k1
Peak Asymmetry:
As = B/A (at 10% peak height)
B = At 10% peak height, the width of a line from the slope to a perpendicular line drawn from the peak's height to the baseline @ 10% height. B is the tailing end of the chromatogram.
A = At 10% peak height, the width of a line from the slope to a perpendicular line drawn from the peak's height to the baseline @ 10% height. A is the fronting part of the chromatogram.
Resolution:
Rs = (1/4)(a-1)(N)1/2[k/(1+k)]
k = the average of two peaks.
Sample Formulae for Chromatography
Efficiency (Theoretical Plates):
N = 5.54 ( tR / w1/2 ) 2
5.54 is a constant when using the "Half Height" method. tR is the retention time of the peak and w1/2 is the width at half height.
Capacity Factor (k'):
k' = (tR — t0) / t0
t0 = (the volume of the mobile phase inside the column) / (Flow Rate)
tR = Band Retention Time
Selectivity (Alpha Value):
a = k2 / k1
Peak Asymmetry:
As = B/A (at 10% peak height)
B = At 10% peak height, the width of a line from the slope to a perpendicular line drawn from the peak's height to the baseline @ 10% height. B is the tailing end of the chromatogram.
A = At 10% peak height, the width of a line from the slope to a perpendicular line drawn from the peak's height to the baseline @ 10% height. A is the fronting part of the chromatogram.
Resolution:
Rs = (1/4)(a-1)(N)1/2[k/(1+k)]
k = the average of two peaks.