how would i find the % ASA in aspirin?

Question

I have to design an experiment that will tell me what percent of the aspirin tablet is ASA. I also have to, in doing this, compensate for the binders in the aspirin. Any chemists out there know what to do? the teacher mentioned something about a titration.

Answer 1

ag, aspirin is itself an ester, though. The para hydroxy group is esterified to reduce the acidity of the molecule.

The best way to determine it, in my book, would probably be by HPLC (High Performance liquid chromatography). We did an experiment in undergraduate analytical chemistry for this purpose ... to figure out ASA in Aspirin.

The main problem, analytically, with aspirin is that the ester group could react with the base. This would create an interference in your result, because you'll use more NaOH than you would otherwise and you'll think the aspirin concentration is higher than it actually is.

Ignoring the ester, the way to recover the ASA is to pulverize (grind up) the aspirin tablet and dissolve it in chloroform (or dichloromethane). Then filter off the insoluble material and evaporate off the chloroform. You could then dissolve the resulting white powder in (pre-boiled) water and titrate with NaOH. The NaOH should be standardized with KHP.

To get rid of the ester, ag is correct. You'd need to react it with concentrated acid (or Lithium aluminium hydride, but I somehow doubt you have that lying around). Then you'd need to use TLC (thin layer chromatography) to make sure that all the ester was converted (by doing a comparison spot with salicylic acid). Then, you'd need to remove the salicylic acid with a separation (chloroform or dichloromethane), evaporate it off, and titrate.

Assuming all of that worked (organic procedures aren't truely analytical, all the time), you could then figure it out.

Answer 2

The ASA occurs in Aspirin in esterified form, you will have to hydrolyse it with standard acid soln. After that, titrate it with NaOH.