Dr.NutriCornell said:

The provenance questions are more useful than the numbers.

Agreed, and mass spec answers a question purity does not: identity. High purity tells you one thing dominates the chromatogram, not that it is the molecule you ordered. A mass within about a dalton of expected is the identity check.

josh_phd_bmore said:

Right, and one flattering data point from a group buy is not consistency.

Bookmarking. The distinction being drawn above is the one nobody else makes.

Dr.NutriCornell said:

The provenance questions are more useful than the numbers.

I am more sceptical of certificates as a category than this thread is. The document tells you about a sample somebody chose to send, at a moment in time, and nothing about the vial in your hand. Independent purchase-and-test is a different quality of evidence and everything else is inference.

SandraNC_45 said:

Eight months with one supplier, then a change in how they communicate that I noticed before I noticed anything about the product.

Shipping damage protocol for vendor vetting orders: if your package arrives with visible damage, temperature excursion, or broken vials:

• Photograph EVERYTHING before discarding packaging
• Note the temperature of the cold pack (liquid = possibly too warm)
• Contact the vendor within 24 hours with photos
• Request a replacement shipment or refund
• Do NOT use potentially compromised medication

Reputable vendors will replace damaged shipments without argument. If they push back, that's a red flag about the vendor.

Moderator note: a couple of off-topic posts removed.