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

The method section is present, which is unusual enough that I want to make use of it.

This is a procedural question rather than a theoretical one, and I would like the procedure rather than the theory.

What I have done so far is read the label documentation where it exists and the two pharmacopoeial monographs that are publicly available, which cover the licensed presentation and say nothing about a research one.

What is the correct sequence, and where is the step that people usually skip?

The underlying point is that if a lot has visibly segregated — some vials showing different appearance — then sampling the top and bottom of the shipment is worth doing.

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.

If the entire lot failed qualification, a retest on a different vial is sometimes done, but reporting a retest result under the same lot number is misleading.

Sampling plans for pharmaceutical manufacturing are defined in ISO 2859 and ANSI Z1.4, and they are based on statistical sampling theory.

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

Assume segregation is possible, and design your sampling to catch it if it exists.

Start from the question: how many vials from this lot do I need to test to claim that the lot meets specification, and the answer depends on both the lot size and the acceptable risk.

For a quantitative result like content, the acceptable range determines how many vials you need to test to establish the lot complies.

Concretely, 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.

The limitation is that you cannot know for certain without testing every vial, and you almost never can afford to do that.

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

The practical consequence is that spot-testing one vial from a new supplier is better than assuming they are all the same.

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

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

I would treat a "complies with" statement without sampling details as a claim rather than as evidence.

If you only pay for one test, pay for quantified content. Purity is the number everyone quotes and content is the number that changes what you do.

edited 22 Mar 2025 by tobias_maartens — clarified the distinction between purity and content

More usefully, 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.

Published segregation failures show that even modern automated processes sometimes produce lots with measurable vial-to-vial variation.

The ICH Q3A and Q3B thresholds for reporting, identification and qualification of impurities are the framework the pharmaceutical industry works to, and they are worth reading even though nothing in the research-grade supply chain is obliged to meet them, because they tell you which numbers a competent analyst would consider worth reporting at all.

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.

In practice: ask for the chromatogram, check the method section, check the lot number against the vial, and set your accept threshold before you see the result rather than after.