Chain of custody records how possession and control of a sample are maintained as it moves between people and locations. It helps connect a laboratory result to the material submitted. It answers a handling question; it does not itself measure purity, identity or content.
Follow the material rather than just the report
The US EPA’s sample and evidence procedure describes custody as both control of material and a record tracing possession from collection. Its environmental investigation context provides a concrete example of this principle, not a universal peptide paperwork requirement.US EPA Region 4 — Sample and Evidence Management (opens in a new tab)
A report number identifies a document. A laboratory sample number identifies material within a laboratory system. A lot number identifies a production grouping. These identifiers may all appear together, but they have different jobs.
| Transition | Useful link |
|---|---|
| Collection to dispatch | Original sample identity and container count |
| Dispatch to receipt | Shipment reference and received identifiers |
| Receipt to preparation | Laboratory accession and preparation records |
| Preparation to result | The analysed portion linked to its original sample |
A complete report with no clear sample link leaves a different uncertainty from a clear sample history with an unsuitable analytical method. One document cannot compensate automatically for the other.
Read handovers and shipping in context
EPA’s procedure records custody transfers with people, dates and times. It explicitly treats common-carrier shipping differently: the carrier does not sign the custody form as a receiving custodian, and shipment identifiers support the transport record.US EPA Region 4 — Sample and Evidence Management (opens in a new tab)
That distinction matters when reviewing a form. An empty carrier signature box is not automatically evidence of a broken chain if the applicable procedure uses another way to document transport.
For an original example, sample S-10 is dispatched in two containers under a recorded shipment reference. The receiving laboratory logs only one container. The immediate question is which container was received and whether the missing one affects the planned analysis.
Do not fill an unexplained handover retrospectively from memory as though it were a contemporaneous record. A later clarification should remain identifiable as a clarification, including who supplied it and on what evidence.
Preserve identity when material is divided or moved
A sample can acquire new identifiers during laboratory work. In an original illustration, S-10 becomes prepared portions S-10-A and S-10-B. Their records should retain the link to S-10 and identify the purpose of the split.
A change of container, removal of a portion or combination with another sample changes the handling history. Without a recorded connection, a later result may be difficult to assign confidently to the original material.
Custody seals can make an opening event apparent, but a seal number is useful only when linked to the relevant container and observation. An intact seal also says nothing directly about the chemical composition inside.
Describe a gap without inventing an event
An unexplained interval may leave access, location or storage conditions uncertain. It does not prove that substitution, contamination or degradation occurred. Equally, the absence of an observed problem does not reconstruct missing history.
A useful review names the gap precisely and asks what record could resolve it: an accession entry, dispatch record, container photograph, seal observation or documented handover. The relevant evidence depends on the missing connection.
The final analytical conclusion should distinguish what was measured from how securely its origin is known. That makes a limitation usable without overstating either the confidence or the suspicion it warrants.
Sources and further detail
- US EPA Region 4 — Sample and Evidence Management (opens in a new tab)
FSBPROC-005-R6, effective 1 July 2024; sections 2.3–2.6 read. Environmental custody procedures are used as an example, including their common-carrier exception. Sample S-10 is fictional.
Sources checked 19 September 2026. Worked examples are illustrative unless a supplied report is explicitly identified. This article has not undergone independent scientific peer review.