What happens when a lot fails testing
Short answer: it doesn't get sold. Here's a real example from TrueVial, whose standard is that every lot must pass identity, purity of 99% or higher, and net peptide content checked against the label, all by an independent lab, before it's made available.
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The standard
- Identity: it's the peptide claimed (mass spectrometry).
- Purity: 99% or higher (HPLC).
- Net peptide content: the actual amount in the vial, compared with the labeled mg.
Purity alone isn't enough, which is why all three are checked. See what purity leaves out.
What the tests showed
Earlier samples from the same source had tested above 99.8% at an independent lab. When new inventory arrived, a vial from each of two lots went to a second independent lab. Identity was confirmed for both. Purity was not:
| Lot | Identity | Purity | Standard | Outcome |
|---|---|---|---|---|
| Lot A | Confirmed | 90.48% | ≥99% | Not sold |
| Lot B | Confirmed | 96.18% | ≥99% | Not sold |
Both lots were made unavailable. Neither is offered for sale.
Sources: the earlier passing reports are dated August 31, 2026, and the two lot reports September 22, 2026. I reviewed all four reports and confirmed each on the issuing lab's public lookup on October 2, 2026. That both lots were made unavailable is TrueVial's written statement to me. Lot numbers and product names are withheld here.
Why it matters
A seller that tests only its first order, or shows one old COA for every shipment, would have sold both lots. Testing every lot against a standard set in advance is what catches it. It's the same question as number 9 on the supplier checklist: what happens to a lot that fails?
Frequently asked questions
What happens when a peptide lot fails testing?
At a supplier with a real standard, it isn't sold. In this example, two lots tested at 90.48% and 96.18% purity against a 99% standard, and both were made unavailable.
What standard does TrueVial test against?
According to TrueVial, every lot must pass identity confirmation, purity of 99% or higher by HPLC, and net peptide content checked against the label, all by an independent lab.
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