[Krnkarina]

Hello, Im a chemistry student at University of Indonesia.
Im currently doing an experiment using glycerin and ethanol
Im searching for glycerin with USP grade and ethanol with ACS reagent grade.

I compare the prices people sell on the internet and the price on sigma-aldrich website.

the internet sell 1 Litre of USP grade glycerine (usually for vaping purpose) for only 21 USD, while sigma aldrich sell it for 205 USD. both said its USP grade and both said its is >99% pure
first I trust sigma aldrich, but then i thought that it has to be USP grade cause ppl use it for vaping, it has to be save for the body.

same goes for ethanol too, ppl sell it (for sterilzing medical tools) a lot cheaper than sigma aldrich. both said its 96% pure and has the same volume. (the one that ppl sell on the internet didnt say its ACS reagant, but its has the same purity persentage)

I am a bit confuse on how this works, I dont know which one to buy. my experiment doesnt involve biomolecule. just simple organic compound.

please help me, thank you 😊

[Arkcon]

You can look up the definition of each term, USP grade and ACS grade.  You've done some other work, comparing the purity, and I can understand your confusion over the nuances.  So here goes:

USP grade means, basically, "food grade."  It can be any purity, even lower than ACS or analytical grade, but the impurities must not be harmful when ingested.  I always tell the story, the one time we bought USP grade for citric acid (kinda by mistake) for an analytical experiment -- it had chunks of wood in it.

The ACS grade may be quite pure, but is not approved for ingestion.  It could be 5 ppm lead, arsenic or dioxin, for example. If those don't affect the possible reactions you have in mind, you can use it.  Maybe it doesn't even have those impurities, but they simply didn't check.

There is also analytical grade,which is even more expensive.  It will have a higher purity, and major impurities will be assayed, and listed on the label.  Only this grade is suitable for and assay, like a titration. 

Whether you can use ACS or USP in your application will depend in the specifics.  As an example, we did use the wood chunk citric acid in our experiment.  It was a dialysis, so we filtered out the chunks (lor else they might pierce the membrane) and ran it anyway.  We were just trying to see if it would work, or if it would damage the product.  We would have bought ACS grade if it were what we wanted next.

You will have to give us the specifics of your application to know if you can get away with USP grade.