Hey? Is anybody listening to the guy's actual question?
The following is an application of GMP and ISO 9000 to USP PG, and should be applicable to all other chemicals too. AFAIK, only USP and ACS grade have compulsory certification, reagent/lab/technical grade is up to you to grade.
2.2.4 Propylene Glycol USP/EP Recertification
Propylene Glycol USP/EP received in bulk can either be stored in an intermediate bulk tank for further use or be packed in drums, IBC’s or smaller packaging before being stored in warehouses, re-shipped or repacked. In such cases of intermediate handling, a recertification process must be applied as follows:
2.2.4.1 Intermediate bulk storage
If the product is unloaded into an intermediate and not emptied (drained) storage tank and/ or mixed with another lot, the initial analytical data are no longer valid. A new lot number must be assigned and a new certificate of conformity must be issued in conformance with the USP/EP requirements. In case a certificate of analysis is required, new analyses must be performed, reporting actual test results.
2.2.4.2 Packaging operations
When bulk product is packed in drums, IBC’s or smaller packaging, each packed lot must be sampled in accordance with an adequate and documented sampling technique (see Chapter 7) and key point controls must be performed on a composite sample representative of the whole lot. If these key point controls are in accordance with the sales specifications and there has been no mixing with another lot, the data mentioned in the certificate of analysis of the bulk product from which the packaging was performed can be passed over to the packed lot and be used for further shipments.
http://www.cefic.be/sector/popg/guide9903/02.htm (http://www.cefic.be/sector/popg/guide9903/02.htm)