Evaluate column resolution:

Problem:

Two substances  X and Y were found to have retention  time 18.50 and 19.80 min., respectively on a 32.0 cm column. An unretained species passed through the column in 1.10min. The peak widths (at base) for X and Y were 1.20 and 1.30 min., respectively. Calculate

a) column resolution,

b) the average number of plates in the column, and

c) the plate height.

Answer:

a)         R =2(t_RY -t_RX)/W_X  - W_Y

R =      2(19.80 - 18.50)/ (1.20 + 1.30) = 1.04

b)         N_X = 16(18.5/1.20)²  

= 3.80 × 10³

N_Y = 1 6 (19.8/1.30)²           

= 3.71 x 10³

N_Av = 3.80 × 10³ + 3.71 × 10³/2

= 3.76 × 10³

c)         H = L/N =30/ 3.76×10³

 = 7.98 × 10³ cm