Chain of custody for laboratory test samples
Have someone acting for the buyer select samples from the identified batch, seal them and record their identity. Log every handover, keep dispatch evidence and ask the laboratory to confirm identities and seal condition on receipt. Retain matched samples under agreed storage conditions. Coordinate this through Cambridge China Bridge.
Agree the sampling brief before collection
Ask the laboratory to confirm the product configuration, tests, sample quantity, containers, handling conditions and whether testing will destroy or alter the sample. Agree how it will record receipt, seal condition and any discrepancy. Put this brief in writing before anyone collects goods.
Our guides on quality inspection and matching bulk production to the approved sample cover inspection planning and physical comparison standards. This guide adds the custody trail connecting the selected production goods to the laboratory result.
Select independently and identify the batch
Use a buyer-appointed inspector or representative who selects the pieces themselves from accessible production stock. Ask the laboratory to advise on a selection method suited to the test and batch. Do not let the factory substitute prepared samples after selection. Record who selected them, where, when and from which cartons or production locations.
Give each sample a unique identifier. Link it to the purchase order, factory, product model, specification revision, colour or material variant, production batch and relevant component lots. Photograph the selected goods beside their labels and source packaging. If the factory cannot identify a batch, record that limitation rather than inventing a reference.
Seal the samples before they leave your control
Use laboratory-approved packaging that protects against contamination, leakage or damage. Apply tamper-evident seals so opening the sample container leaves visible evidence. Record the seal identifiers against the sample identifiers, then photograph the closed packages with those references readable.
Keep selected samples under the representative's control until sealed and handed over for dispatch. If access is necessary afterwards, record who opened the package, why and when, with photographs and replacement seal details. Keep the original record; do not overwrite it to make the custody trail appear uninterrupted.
Record dispatch, handovers and laboratory receipt
Keep a custody record showing each sample identifier, seal reference, sender, recipient, handover date and time, purpose and storage location between transfers. Ask those handing over and receiving samples to acknowledge the transfer. Keep the packing list, courier tracking reference, collection receipt and delivery confirmation alongside it.
The Government Chemist's referee-analysis example recommends courier or tracked post for sample transport. That example concerns food disputes; use tracked transport as a practical control for your commercial samples. Send the laboratory the sample list and seal photographs separately, and request confirmation of the identifiers, seal condition and any damage on arrival.
Retain matched samples and resolve gaps
Select retained samples during the same collection from the same identified batch. Label and seal them separately, with references linking them to the submitted samples. Agree their holder, storage conditions, retention period and authority to open or dispose of them. Ask the laboratory what material will remain after testing. A retained sample supports comparison but may differ from the tested piece.
If a seal is broken, an identifier differs or a handover is missing, ask the laboratory to photograph and hold the affected sample pending instructions. Record the gap and agree whether testing remains useful or fresh independent sampling is needed. Match the report's sample references to the custody record before using the result. Our report comparison guide explains the limits of other factory checks; a custody trail alone does not prove the whole batch conforms.
Frequently asked questions
Can the factory choose the laboratory samples?
For independent selection, appoint someone acting for you to pick from the identified batch. Factory-selected samples can still be tested, but record their origin and do not describe the selection as independent.
What should a sample custody record contain?
Record sample and seal identifiers, batch and order references, selection details, each sender and recipient, transfer dates and times, storage locations, dispatch evidence and laboratory receipt checks.
What if the laboratory receives a broken seal?
Ask it to photograph the package and hold the sample pending instructions. Record the discrepancy and agree whether to test with that limitation or collect fresh samples independently.
How long should I keep retained samples?
Agree the period with the laboratory and buyer before collection, considering sample stability, storage conditions, destructive testing and likely disputes. Record who can authorise opening or disposal.