4. A tablet weighing 1000 mg was analyzed for caffeine and paracetamol content. The tablet was
crushed by a solvent mixture (methanol 50%, water, 50%), 100 mg of phenacetin was added as
the internal standard. The solution was then made up to 100 mL and subsequently analyzed by
HPLC. A solution of a mixture of stan was also analyzed. This solution was obtained by taking
250 mg of each component and dissolving, making up to 100 mL using methanol water (S shown
in Table below calculate the composition of the tablet. Note that the tablet contains the three
active compounds and a binder. dard 0:50). Using the results un 1 Standard Mixture (25% w/w
of each Parcetamol Caffeine Aspirin Phenacetin Tablet Solution Paracetamol Caffeine tr 1.51
min 38,801 tr 2.10 min 14,236 tr-2.65 min 26,30 tr 3.70 min 39,594 Run 2 tr- 1.54 min68,994 tr-
2.11 min 19,050 tr- 2.70 min 53,480 tr 3.80 min 84,927 Aspirin Phenacetin (internal standard)
Solution
Concentration of phenacetin in sample =100mg /100 ml = 1mg /ml = 1000 mg / l
Area corresponding to 250 mg/l phenacetin =39,594
So, we calculate the response factor F,
Area of analyte/ concentration of analyte = F ( area of standard/ concentratio of standard)
so we get, 84922/1000 = F( 39594/250)
or F= 0.536
so using the above formula we calculate unknown concentrations of paracetamol, caffeine and
aspirin
i. Paracetamol................> 68994/ x = 0.536 (38801/250) = 829.36 mg/l
ii. Caffeine.........................> 19050/x = 0.536( 14236/250) = 624.14 mg/l
iii. Aspirin.............................> 53480/x= 0.536 (26301/250) = 948.4 mg/l
The total volume was 100 ml. So amount of each compound in 100 ml:

Paracetamol = 82.936 mg
Caffeine= 62.414 mg
Aspirin = 94.84 mg
So % composition in a 1000 mg tablet comes out as:
Paracetamol = 8.2936 % ... (answer)
Caffeine = 6.2414% ... (answer)
Aspirin = 9.484% ... (answer)
Hope this Helps!!