The case in front of me: HJ · liraglutide.
I have two candidate explanations and no way to distinguish them.
The same procedure has worked without incident several times previously, which argues against technique.
How do I distinguish the benign explanation from the one that matters?
A certificate that reports one test result on one vial extrapolates to claim that all two hundred vials in the lot are identical, which is an assumption worth questioning.
Under AQL sampling plans, testing two vials from a fifty-vial lot gives you an operating characteristic curve that tells you what risks you are accepting.
| Test | Answers | Does NOT answer |
|---|---|---|
| RP-HPLC, area % | What fraction of detected material is the target | How much target is present |
| Quantified content | Milligrams of peptide per vial | What the impurities are |
| ESI-MS identity | Whether the molecular weight matches | Purity, or isomeric substitution |
| Peptide mapping | Sequence, localised to a fragment | Quantity |
| Karl Fischer | Water content of the solid | Solvent content |
| LAL endotoxin | Pyrogen load in EU/mg | Sterility |
| Sterility test | Growth in defined media over 14 days | Endotoxin, or bioburden count |
Specifically, published segregation failures show that even modern automated processes sometimes produce lots with measurable vial-to-vial variation.
I would treat a "complies with" statement without sampling details as a claim rather than as evidence.
If testing multiple vials, state how many you tested and why you chose those vials.
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
Browse resultsThermal history during shipping is different for every vial, so a lot that experienced thermal abuse may have internal variation even if it was originally homogeneous.
Testing a vial that has been open in the lab for three months is testing aged material, not the fresh lot, and the result should be explicitly noted as a retest.
On the detail: the statistical foundation here is well-established, which is why sampling plans from decades ago are still valid.
The limitation is that you cannot know for certain without testing every vial, and you almost never can afford to do that.
Assume segregation is possible, and design your sampling to catch it if it exists.
edited 10 Dec 2024 by dmitri_savchuk — added the placebo-arm figures
The single most misleading statement on a research-grade certificate is a lot number with no statement of how many vials from that lot were tested.
Stratified sampling — testing one vial from the top, one from the middle, and one from the bottom of a shipment — is cheap insurance against segregation.
Worth being precise here: acceptance Sampling by Attributes defines the number of samples you need from a lot to claim a specified quality level at a specified risk — it is in ANSI standard Z1.4.
Lyophilised peptide homogeneity studies show that vial-to-vial variation is usually small but occasionally large, depending on the distribution in the freeze-dryer.
The practical summary: a lot number without a sampling statement is a lot number without meaning.
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.