Resolution Factor, Tailing Factor, Theoretical Plates and Capacity Factor in HPLC
Formula and calculation for resolution factor, tailing factor, theoretical plates and capacity factor in HPLC analysis of pharmaceutical products as per usp chromatography.
Resolution factor:
Resolution factor shows the accuracy of the quantitative analysis and resolution factor should be greater than 1.5 or specified in the individual monograph. Resolution factor can be calculated by following formula:

 R =                  2(t2-t1)                
              2.70 (W1h/2+W2h/2)

 W = Peak width
h = Hight
t1 = Retention time of first peak
t2 = Retention time of second peak

 Related: Calculation of Relative Response Factor (RRF)

 Tailing factor:
It should meet the requirements of the individual monograph and can be calculated by following formula:

 T = W 0.05
          2F

 W0.05 = Peak width at 5% high
F = Leading edge of the peak

 Theoretical Plates:
The number of Theoretical Plate represents the column efficiency. It should meet the value given in the monograph. It can be calculated by the following formula:
n = 16(t)2    or   5.54x (t)2
        (W)2          (W1/2)2
Capacity factor:
K= t – 1
     tα

 t = Retention time of second peak (active)
tα = Retention time of first peak (impurity)