Question

The chromatogram below shows the separation of components in an over-the-counter pain reliever. 1: acetaminophen, 3.97 min, wrz 0.12 min 2: caffeine, 4 6.15 min, w/2 0.21 min 3: benzoic acid, t 9.73 min, w2 0.35 min 4: aspirin, 14.8 min, W1r2 0.73 min 1012 14 16 min Calculate the number of theoretical plates N for the peaks of caffeine and benzoic acid. caffeine benzoic acid Number Number Continued below

Answer 1

To calculate the number of plates, consider the half peak height, N = 5.54 (t_r/W_1/2)^2 where t_r is retention time w is peak width = 5.54 (6.15/0.21)^2 = 5.54 times 857.65 N = 4751.38 The number of plate for the caffeine is 4751.38 Now, calculate the number of plates for benzoic acid. N = 5.54 (9.73/0.35)^2 = 5.54 times 772.84 N = 4281.4 The number of plates for the benzoic acid is 4281.5 let's calculate the resolution between caffeine and benzoic acid. R = 2 [t_r (benzoic acid) - t_r (caffeine)]/1.70 [w_1/2 (benzoic acid) - w_1/2 (caffeine)] = 2 ((9.73) - (6.15))/1.70 (0.35 - 0.21) = 7.16/0.238 R = 30.08