Results:
Identify and mark the signals in the spectra and note the chemical shift values of the methyl resonances in aspirin and caffeine and the methylene resonance in s-trioxane.
Using above expression, calculate the weight of aspirin and caffeine in one tablet, and the percentage w/w of each component in one analgesic tablet.
Whole tablet weighed = 0.501
Half tablet weighed = 0.270
Mass of s-trioxane = 0.05
RMM of aspirin = 180
RMM of caffeine = 194
RMM of s-trioxane = 90
No. of moles of components = component integral/no. of protons giving signal
No. of moles of standard standard integral/ no. of protons giving signal
To find out the weight and percentage w/w of Aspirin and Caffience following calculations were made:
Aspirin:
No of moles of components (x) = ?
No of moles of standard = mass of s-trioxane / RMM of s-trioxane
= 0.05 / 90 = 0.000555
Component integral = 202.72
No of protons giving signal = 3
Standard integral = 200
No of protons giving signal = 6
Putting values in the above eq.1:
x / 0.000555 = (202.72/3) / (200/6)
x/0.000555 = 67.57 / 33.33
x = 67.57 x 0.000555 / 33.33
x = 0.00113 moles
Mass of aspirin = moles x RMM
= 0.00113 x 180 = 0.203g = 203mg
% w/w of aspirin in the tablet = mass of aspirin / mass of the tablet x 100
= 0.203 / 0.501 x 100
= 40.5%
Caffeine:
No of moles of components (x) = ?
No of moles of standard = mass of s-trioxane / RMM of s-trioxane
= 0.05 / 90 = 0.000555
Component integral = 14.0
No of protons giving signal = 3
Standard integral = 200
No of protons giving signal = 6
Putting values in the above eq.1:
x / 0.000555 = (14.0/3) / (200/6)
x/0.000555 = 4.66 / 33.33
x = 4.66 x 0.000555 / 33.33
x = 0.0000775 moles
Mass of caffeine = moles x RMM
= 0.000075 x 194 = 0.0145g = 14.5 mg
% w/w of aspirin in the tablet = mass of aspirin / mass of the tablet x 100
= 0.0145 / 0.501 x 100
= 2.89%
Discussion:
References:
