Chain of custody in laboratory submissions: what it is and why it matters
Chain of custody is one of those phrases that appears on every laboratory submission form but rarely gets explained. For clients submitting samples for regulatory purposes, a broken chain of custody can invalidate results that took days to generate. This article explains what the documentation actually records and how to handle it correctly.
What chain of custody records
A chain-of-custody (COC) form records the identity of every person who had physical possession of a sample from the moment of collection to the moment of analysis. It captures: who collected the sample, when and where it was collected, what container type was used, what preservative (if any) was added, the temperature at collection, and the signature of each person who transferred custody.
The purpose is to establish that the sample analysed in the laboratory is the same sample that was collected in the field, and that it was handled in a way consistent with the method requirements. If a regulator or a court needs to rely on the result, the COC is the document that supports its integrity.
Common errors that create problems
The most frequent errors are: leaving the collection time blank, failing to record the sample temperature at collection, using a container type that does not match the method requirement, and not signing the transfer section when handing samples to a courier. Any of these can prompt a regulator to question the result, even if the analysis itself was performed correctly.
A second common issue is submitting samples without a COC form at all, or with a form that does not match the sample labels. If the sample ID on the bottle does not match the ID on the form, the laboratory has to contact the client to resolve the discrepancy before analysis can begin, which delays turnaround.
- Leave no field blank. Write N/A if a field does not apply
- Record collection time to the nearest minute
- Sign and date every custody transfer
- Match sample IDs on bottles exactly to IDs on the form
- Note any deviation from the standard collection procedure
How the laboratory uses the COC
At intake, the laboratory checks the COC against the physical samples: container type, label, condition, and temperature. Any discrepancy is noted on the form and the client is contacted. The intake number assigned by the laboratory is then linked to the COC, and that number travels with the sample through every stage of analysis.
The COC is retained as part of the project record and is available to the client on request. For regulatory submissions, we can provide a copy of the signed COC as an appendix to the analytical report.
If you are filling out a COC form for the first time, contact us before you go to the field. Five minutes on the phone can prevent a documentation problem that takes a week to resolve.