The United States Pharmacopeia (USP) is an official public standards–setting authority for all prescription and over–the–counter medicines and other health care products manufactured or sold in the United States. USP also sets widely recognized standards for food ingredients and dietary supplements. USP sets standards for the quality, purity, strength, and consistency of these products–critical to the public health. USP is a non-governmental, not-for-profit public health organization.
USP has updated section <467> Residual Solvents. The new guidelines and procedures became official on July 1, 2008. This general chapter applies to existing drug substances, excipients, and products.
Solvents are put into three categories: Class 1 - To Be Avoided (benzene, some chlorinated solvents, etc.), Class 2 - To Be Limited (methanol, acetonitrile, toluene, etc.), and Class 3 - Low Toxic Potential ( acetone, ethanol, etc.). Two options are available for describing limits for these solvents.
But these options all require testing of components to determine the actual levels of solvents. And each manufacturer is required to state which solvents are likely to be present (based on manufacturing procedures). So, someone will have to do the testing. And it looks like that responsibility is going to fall to each individual manufacturer.
The actual <467> method involves headspace extraction followed by gas chromatographic analysis. Since this is the Analytical Chemistry forum, we will be most concerned about the actual procedural details, but we can also discuss other interpretation issues, if that is what interests everyone.