Certified ACS: safe to use?

[Flaklaflubillibu]

From this source, although not where I would buy:

ACS grade: A chemical grade of highest purity and meets or exceeds purity standards set by American Chemical Society (ACS)

USP grade: A chemical grade of sufficient purity to meet or exceed requirements of the U.S. Pharmacopeia (USP); acceptable for food, drug, or medicinal use; may be used for most laboratory purposes

Anyone use ACS grade glycerol instead of USP grade VG (glycerol and glycerin are technically the same thing)?
Any reason NOT to use ACS grade?

In my opinion, I think it would be even safer to use, but I would like to hear what others here know/think. TIA

 

[Flaklaflubillibu]

Reason I am asking is I can get the ACS grade for about $10 per 500 ml bottle, whereas I would be looking at about $5 per 177 ml (6 oz) bottle at CVS, in the skin care aisle.

 

[Stosh]

This may shed some light : Useful Chemical Grade Designations from The Science Company, although I am NOT a chemist and don't play one on TV even....

 

[Flaklaflubillibu]

I decided to do a comparison of the "Certificate of Analysis" sheets for a USP Glycerol and an ACS Glycerol, both sold through Fisher Scientific. Here are the assays specified on each sheet:

USP
APPEARANCE
ASSAY
CHLORIDE
CHLORINE COMPOUNDS
COLOR
DEG & REL INDIVD.
DEG & REL. TOTAL
FATTY ACID ESTERS
HEAVY METALS (as PB)
IDENTIFICATION (ALL LISTED)
IGNITION RESIDUE
RESIDUAL SOLVENTS
SPECIFIC GRAVITY
SULFATE (SO4)
WATER

ACS
APPEARANCE
ACROLEIN,GLUCOSE,NH4
ASSAY
CHLORINE COMPOUNDS
COLOR
FATTY ACID ESTERS
HEAVY METALS (as Pb)
IDENTIFICATION
IGNITION RESIDUE
NEUTRALITY
SUBSTANCES DARKENED BY H2SO4
SULFATE (SO4)
WATER

For the two particular COA sheets I looked at, the test values given for each assay (where the same assay was done for both products) were essentially the same for both products.

As you can see USP assays for "CHLORIDE", "DEG & REL INDIVD.", "DEG & REL. TOTAL", and "SPECIFIC GRAVITY", whereas ACS does not. On the other hand, ACS assays for "ACROLEIN,GLUCOSE,NH4", "NEUTRALITY", and "SUBSTANCES DARKENED BY H2SO4", whereas USP does not.

One is labeled for human consumption (USP) and the other (ACS) is not, but this may be a legal technicality only.

I will stick with USP since there is this dark cloud of not-for-human consumption lingering over the ACS grade, but if any one knows the real difference, if any, between these two products, that would be helpful to know.