Sending a Sample to a Laboratory: Packaging, Splitting and Chain of Custody from the Buyer's Side

Send the laboratory a sealed, unopened container carrying your own sample identifier, packed in tamper-evident packaging, with a completed custody form inside and the contents declared accurately on the consignment — and keep a second sealed container from the same lot at home as a reserve. Those five things are what let a result be tied, afterwards, to the material you hold. Without them a report may be accurate and still prove nothing about your lot.

This is the buyer's how-to for the outbound journey. It is not the standard for custody records, which is covered in depth by the handbook page on the custody record ISO/IEC 17025 expects, and it is not the inbound chain from supplier to buyer, which has its own article in this store. It covers only what you do between deciding to test and the laboratory signing for the package.

Why chain of custody exists, and what it protects

ASTM D4840 defines sample chain of custody as the process by which a sample is kept under physical possession or control through its whole life, from collection to disposal, and says the documentation exists to support data and conclusions later ^[2]. ISO/IEC 17025 approaches the same requirement from the laboratory's side: it must have a procedure for the transport, receipt, handling, protection, storage and retention of test items, protecting the interests of both the laboratory and the customer ^[1]. The record earns its keep in one situation: a surprising result, and the question of whether the sample tested was the sample sent, in the state it was sent. A continuous record answers that. A gap leaves it open permanently.

Splitting a sample and retaining a portion

For lyophilised material in sealed containers, do not split by opening one and dividing the powder. Opening a container outside a controlled environment exposes the solid to moisture and contamination, which is the very thing some tests measure. Split by container instead: send one or more sealed units and retain at least one sealed unit from the same lot. Regulated manufacturing keeps a reserve sample of each lot for exactly this reason ^[5]; for a buyer, the reserve is what allows a second opinion, a second laboratory, or a conversation with the supplier grounded in material both sides can have tested.

• Photograph every container, sent and retained, with the lot string and seal legible.
• Record which unit went where, under which identifier, on which date.
• Store the reserve exactly as the laboratory unit was stored before dispatch, and log that location.
• If a test needs an unopened container, such as endotoxin or bioburden, send that container sealed and untouched.

Labelling, sealing and the custody form

Choose one sample identifier and use it everywhere: on a label applied to the container without covering the supplier's lot string, on the laboratory's submission form, and on the custody form. ISO/IEC 17025 requires the laboratory to keep items identified unambiguously while they are in its care ^[1], and your identifier becomes the thread the laboratory attaches its own to. No carrier signs a custody form at every hub, so the record needs a substitute for transit: seal the outer package with tamper-evident tape, record the seal's condition at closure, and ask the laboratory to record it again at opening ^[2].

Put the form in its own sealed envelope inside the outer package, and keep a photograph or copy. The custody form travels with the sample; your copy stays with the reserve.

Packing the container itself

Pack in layers, so that damage to one layer does not reach the sample. The container goes first into a sealed, leak-proof bag or secondary container with enough absorbent or cushioning material to hold it still; the secondary container goes into a rigid outer box; and the custody form travels in its own envelope between the two, where it can be read without disturbing the sample. Carriers that accept laboratory samples generally expect this structure in some form, and a laboratory's intake instructions will say if it needs anything more specific ^[3].

1. Wrap each sealed container individually so that glass cannot touch glass.
2. Place it in a sealable bag or secondary container, with a small desiccant sachet if the laboratory permits one.
3. Add cushioning so nothing moves when the box is shaken.
4. Put the custody form, in its own envelope, on top of the secondary container.
5. Close the rigid outer box and seal every seam with tamper-evident tape ^[2].
6. Photograph the sealed package from two sides before handing it to the carrier.

If the sample is crossing a border, allow for it. A consignment to a laboratory in another country is subject to the same import rules as any other shipment, may be held for inspection, and will take longer than the carrier's standard estimate. Ask the laboratory, before you pack, whether it accepts samples from your country and what paperwork it needs to receive them; then build the likely delay into any temperature plan and into your expectations of turnaround.

Temperature during transit

Follow the laboratory's instruction rather than guessing. Many laboratories accept sealed lyophilised material at ambient temperature for a short journey; some ask for refrigerant packs for longer routes or particular materials. Where cold transit is required, the container needs to be qualified for the route and duration — WHO guidance on shipping containers exists because an insulated box holds temperature only for the time and conditions it was tested against ^[4]. Record what you packed, the refrigerant used, and the time of dispatch. If you can include a small temperature logger, do; it turns a question about transit into a record.

Declaring contents accurately on the consignment

The consignment is declared exactly as what it is. Whether a given material may travel by a given carrier, and on what conditions, is set by that carrier's published rules; for United States mail, for example, Publication 52 sets out what is hazardous, restricted or perishable and how each may be mailed, if at all ^[3]. Whether the laboratory can accept the material from where you are is a question for the laboratory's intake team, and it is worth asking before you pack. If either the carrier or the laboratory says the material cannot be accepted, it does not travel; a sample that arrives outside the rules has no evidential value in any case.

What invalidates a result before testing begins

Laboratories check a package against acceptance criteria at receipt, and a sample can be rejected, or tested with a qualified report, before any analysis starts; the acceptance criteria a laboratory applies at receipt are set out in the handbook. From the sender's side, these are the usual causes ^{[1] [2]}.

• An identifier on the container that does not match the form, or no identifier at all.
• A broken, missing or unrecorded seal on the outer package.
• A container that has been opened, when the test requested needs it unopened.
• A temperature instruction that was not followed, with no record of what was done instead.
• Tests requested on the form that differ from the quote, or a missing form.
• Too little material for the tests requested.

Closing the chain

When the report arrives, check that it carries your identifier and the dates of receipt and analysis ^[1], file it against the lot with your custody copy and photographs, and record what the laboratory will do with any remaining material — return, retention period or disposal ^[2]. Keep the reserve until you are satisfied the result will not be questioned. The chain is complete when every step from your shelf to the laboratory's disposal record can be read back without a gap.