How do I trace an SSA lot number back to a synthesis date?

I have the report as a PDF with the chromatogram on page two, so I can quote specifics.

I want a method I can write down and repeat, not a rule of thumb.

I would rather over-engineer this than discover a problem later, within reason.

Which parts of this are load-bearing and which parts are habit?

Most suppliers test one vial per lot and report the result as lot homogeneity, which is sampling one item from one lot and extrapolating wildly.

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.

The sample size determination requires choosing a confidence level and an acceptable error rate, and the smaller the error rate you want, the larger your sample must be.

Worth noting that thermal excursions during shipping affect different vials differently, so the lot may not be homogeneous even if it left the factory that way.

If testing multiple vials, state how many you tested and why you chose those vials.

edited 8 Aug 2026 by m_haraldsen — reworded for clarity after a comment

Specifically, batch testing establishes what can be claimed about the lot as a whole, and the sample size determines how much you can actually claim.

A statement that "lot 20260412 complies with specifications" is meaningless without stating which vials from the lot were tested and how many there were.

On the detail: if the lot was manufactured in multiple batches, testing vials from each batch separately establishes whether batch-to-batch variation is acceptable.

Lyophilised peptide homogeneity studies show that vial-to-vial variation is usually small but occasionally large, depending on the distribution in the freeze-dryer.

One qualification: testing more vials gives better confidence, but at some point the cost outweighs the benefit.

The practical summary: a lot number without a sampling statement is a lot number without meaning.