Calculation of peak asymmetry and symmetry

Asymmetry

Peak asymmetry is calculated by comparing the peak half-widths at 10% of the peak height:

where

A_S	Asymmetry 10%
W_10	Peak width at 10% of the peak height
W_f, 10	Front half of the peak width at 10% of the peak height.

Figure Calculation of peak asymmetry

Symmetry

By most of the pharmacopeias, the symmetry factor of a peak is calculated by comparing the peak half-widths at 5%. In OpenLab, this factor is calculated and stored as the Tailing factor (see Symmetry factor, tailing factor (USP)). In OpenLab, the symmetry is calculated as a pseudomoment by the integrator using the following moment equations:

If no inflection points are found, or only one inflection point is reported, then the peak symmetry is calculated as follows:

where

a_i	Area of slice
t_i	Time of slice
H_f	Height of front inflection point
H_r	Height of rear inflection point
H	Height at apex

Figure Calculation of the Peak Symmetry Factor