The material a preclinical study actually tested

Characterization is per batch, and the definition of batch depends on it

The requirement is one sentence long and it does more work than any other sentence in the good laboratory practice rules. The identity, strength, purity, and composition or other characteristics which will appropriately define the test or control article shall be determined for each batch and shall be documented.

Each batch. Not each substance, not each shipment, not each supplier. The definitions section closes the loop: batch means a specific quantity or lot of a test or control article that has been characterized according to the characterization section. A quantity of material that has not been characterized is, under this rule, not yet a batch.

A second sentence follows and is easy to skip. Methods of synthesis, fabrication or derivation of the test and control articles shall be documented by the sponsor or the testing facility. How the material was made is part of the record, not a supplier's private matter.

There is one shortcut, and it is narrow. Where marketed products are used as control articles, those products are characterized by their labelling. A licensed, labelled product carries its own identity documentation; an unlabelled powder does not.

A test article, in these rules, means any food additive, colour additive, drug, biological product, electronic product, medical device for human use, or other article subject to regulation. A control article means an equivalent article, other than a test article, feed or water, administered to the test system for the purpose of establishing a basis for comparison. Both are characterized to the same standard.

What has to be on the storage container, and what has to be kept

The rule prescribes the label. Each storage container for a test or control article shall be labeled by name, chemical abstract number or code number, batch number, expiration date, if any, and, where appropriate, storage conditions necessary to maintain the identity, strength, purity and composition of the article.

That is five elements, and the batch number is the one that ties the container back to the characterization data. A container without a batch number cannot be matched to the analysis that defined what is inside it.

One further sentence closes a loophole that would otherwise swallow the rule: storage containers shall be assigned to a particular test article for the duration of the study. A container is not re-used mid-study for something else.

For studies of more than four weeks' duration, reserve samples from each batch of test and control articles must be retained for the period the record retention section provides. That means physical material is kept, not only paper. If a question arises later about what was actually administered, there is something left to test.

The retention rule carries its own realism about perishable material. Wet specimens, samples of test or control articles and specially prepared material that are relatively fragile and differ markedly in stability and quality during storage are retained only as long as the quality of the preparation affords evaluation — and in no case longer than the periods the section otherwise sets.

Separation supports all of this physically. As necessary to prevent contamination or mix-ups, there must be separate areas for receipt and storage of test and control articles, for mixing them with a carrier, and for storage of the resulting mixtures. Those storage areas must be separate from areas housing the test systems, and adequate to preserve the identity, strength, purity and stability of the articles and mixtures.

Stability has to be established, and there are exactly two ways to do it

The stability of each test or control article must be determined by the testing facility or by the sponsor, by one of two routes. Before study initiation. Or concomitantly, according to written standard operating procedures which provide for periodic analysis of each batch.

The second route is the interesting one. It permits a study to begin before the stability picture is complete, on condition that the analysis runs alongside the study on a written schedule. What it does not permit is stability being assumed, or inferred from a supplier's claim, or established retrospectively after the study is finished.

Stability matters for a specific reason in this context. A safety study administers a defined quantity of a defined substance over a defined period. If the substance degrades in storage, the quantity administered on the last day is not the quantity administered on the first, and the exposure the study reports is not the exposure the animals received. Peptides are particularly exposed to this, which is why the storage-condition element on the container label exists.

Reagents and solutions in the laboratory areas have their own short rule, and it reads like a warehouse instruction because that is what it is. All reagents and solutions must be labelled to indicate identity, titer or concentration, storage requirements, and expiration date. Deteriorated or outdated reagents and solutions shall not be used.

Equipment sits behind both. Equipment used in the generation, measurement or assessment of data must be adequately inspected, cleaned and maintained, and must be adequately tested, calibrated or standardised. Written records must be kept of all inspection, maintenance, testing, calibrating and standardising operations, with the date, and non-routine repairs must be documented with the nature of the defect, how and when it was discovered, and any remedial action taken.

Mixtures with a carrier: uniformity, concentration, and the earliest date

Very little material is administered neat. Most test articles reach a test system dissolved, suspended or mixed into a carrier, and the rule treats that mixture as a separate object requiring its own analysis.

For each test or control article mixed with a carrier, tests by appropriate analytical methods must be conducted to determine the uniformity of the mixture, and to determine periodically the concentration of the article in the mixture. Uniformity and concentration are different questions. Uniformity asks whether the material is evenly distributed. Concentration asks how much is there. A mixture can be perfectly uniform at the wrong strength, or the right average strength while separating in the container.

Stability in the mixture is a third question and gets the same two-route treatment as the article itself: determined either before study initiation, or concomitantly according to written standard operating procedures providing for periodic analysis of the articles in the mixture.

The rule then addresses the case where the mixture has multiple dated components. Where any component of the article-and-carrier mixture has an expiration date, that date must be clearly shown on the container. If more than one component has an expiration date, the earliest date shall be shown. The mixture expires when its first component does.

The protocol requirement reinforces the same concern from another direction. A protocol must include a description or identification of the diet used, as well as the solvents, emulsifiers and other materials used to solubilise or suspend the articles before mixing with the carrier — and must include specifications for acceptable levels of contaminants reasonably expected to be present in the dietary materials and known to be capable of interfering with the study.

Handling, and what a published paper usually does not say

The handling section is four clauses and reads as a chain-of-custody requirement. Procedures must be established for a system that ensures proper storage; that distribution is made in a manner designed to preclude the possibility of contamination, deterioration or damage; that proper identification is maintained throughout the distribution process; and that the receipt and distribution of each batch is documented, including the date and quantity of each batch distributed or returned.

Read together with the characterization and labelling rules, the effect is that a regulated safety study can answer a question that most published animal work cannot: exactly which batch of material, characterized in exactly which way, went into exactly which experiment on exactly which date.

Management carries this as an explicit duty rather than leaving it to the bench. Testing facility management must assure that test and control articles or mixtures have been appropriately tested for identity, strength, purity, stability and uniformity, as applicable. Those five words are the standard the material is held to before the science begins.

None of this is a checklist to look for in a journal article, because journals do not require it and papers rarely carry it. A methods section that names a supplier and a stated purity is doing more than many, and still leaves open the batch, the characterization method, the stability data, the carrier analysis and the chain of custody. That gap is not evidence of anything wrong. It is a description of what the published record does and does not contain.

The practical consequence for reading preclinical evidence is a narrower one than it might seem. Where a published animal study of a peptide reports an effect, the compound named in the title is a claim about what was in the vial, supported by whatever documentation the authors happened to have. Where a study was run to support a regulatory filing, that same claim is supported by per-batch characterization, a labelled container, documented synthesis, a retained reserve sample and a documented distribution record. Both may be true. Only one of them is verifiable from the outside.

Sources

Each document below is named as it names itself, with the date printed on that document rather than the day it was read.

1. 21 CFR 58.105 — Test and control article characterization, read in full for the per-batch determination of identity, strength, purity and composition, the documentation of synthesis methods, the labelling of the marketed-product exception, the two routes to establishing stability, the five required storage container label elements, the container assignment rule, and the reserve sample requirement for studies over four weeks — Electronic Code of Federal Regulations, National Archives and Records Administration, September 2026
2. 21 CFR 58.107 — Test and control article handling, read in full for the four-part handling system: proper storage, distribution precluding contamination, deterioration or damage, identification maintained through distribution, and documentation of the receipt and distribution of each batch with date and quantity — Electronic Code of Federal Regulations, National Archives and Records Administration, September 2026
3. 21 CFR 58.113 — Mixtures of articles with carriers, read in full for the separate uniformity and periodic concentration testing requirements, the two routes to establishing stability in the mixture, and the rule that where more than one component carries an expiration date the earliest date must be shown on the container — Electronic Code of Federal Regulations, National Archives and Records Administration, September 2026
4. 21 CFR 58.3 — Definitions, read for the definitions of test article, control article and batch, the last of which defines a batch as a quantity characterized under the characterization section — Electronic Code of Federal Regulations, National Archives and Records Administration, September 2026
5. 21 CFR 58.47 and 58.83 — Facilities for handling test and control articles and Reagents and solutions, read for the required separate areas for receipt and storage, mixing and mixture storage, the separation from areas housing test systems, and the four labelling elements required on every reagent and solution together with the bar on using deteriorated or outdated ones — Electronic Code of Federal Regulations, National Archives and Records Administration, September 2026
6. 21 CFR 58.63 — Maintenance and calibration of equipment, read for the requirement that data-generating equipment be tested, calibrated or standardised, and for the written records of inspection, maintenance and non-routine repair including the nature of the defect and when it was discovered — Electronic Code of Federal Regulations, National Archives and Records Administration, September 2026