Can I separate acetic anhydride from asprin?

Yes, you can.
If the question involves just separating acetic anhydride from aspirin (acetylsalicylic acid) then it is rather simple (I think). If you are wanting to separate acetic anhydride from an aspirin tablet then it is slightly more complicated (as I don’t know what else aspirin contains) but the principle of separating these should be the same.
Let’s look at the two molecules:
1) Aspirin
2) Acetic Anhydride
One of the main differences between the two (that we shall exploit in this method) is that aspirin has an acid group whereas the Acetic anhydride has no acid or base groups.
Procedure
1) Dissolve the mixture in diethyl ether. Both compounds have a high solubility in this .
2) Extract the ether solution with dilute (2 molar) sodium hydroxide solution
NOTE: You can do extractions with one strong and one weak base to separate strong and weak organic acids but If you only have these two compounds then I assume you will only need one base to remove the Aspirin.
Now you have separated the , you want to get the compounds out of solution:
Aspirin
You have aspirin in the base extract.
3) Neutralize the extract with dilute (2 molar) hydrochloric acid. This will precipitate the aspirin.
4) Filter the aspirin from the neutralized mixture using vacuum filtration and redissolve it in diethyl ether.
5) Dry the compound by adding magnesium sulphate. Then filter off the solid using vacuum filtration.
6) Remove the ether by rotary evaporation. Now you will have solid aspirin. You may purify this by re-crystallization if you wish.
Acetic Anhydride
The acetic anhydride is in the ether residue.
3) OPTIONAL. Wash the ether residue with water. Then remove the water using a separation funnel.
4) Dry the ether using Magnesium sulphate. Then filter off the solid using vacuum filtration.
5) Remove the ether by rotary evaporation. Now you will have liquid acetic anhydride.