How to Pack Samples for Postal Submission to a Lab

A sample that arrives broken, leaking, or unlabelled cannot be tested. It also cannot be returned in a useful state. Postal submission to an analytical lab is straightforward if you follow a few consistent rules, but those rules are not always obvious to clients who are new to the process. This guide covers the basics.

Containers and sealing ¶

Use glass or HDPE containers for liquid samples. Avoid polystyrene for anything that contains solvents, as the solvent will dissolve the container in transit. Seal with a lid that has a liner, not a bare plastic cap. If you are unsure whether the lid will hold, wrap the container in Parafilm before placing it in a zip-lock bag.

Solid samples can go into zip-lock bags or screw-top glass jars. If the solid is hygroscopic, include a small desiccant sachet and seal the bag before the outer packaging.

Labelling ¶

Label the container itself, not just the outer packaging. If the outer packaging is removed or damaged in transit, the container needs to be identifiable on its own. Include: your name or company name, the sample reference number provided by the lab, and a brief description of the contents.

Do not write 'unknown substance' on a container without any other information. If the material has known hazards, include a hazard label on the container and a safety data sheet inside the outer package.

Documentation inside the package ¶

Include a printed note with: the sample reference number, what the material is, how it was stored before posting, and what you need to know. If you have already exchanged emails with the lab, a printout of the relevant email thread is sufficient. The analyst should not have to search their inbox to understand what arrived.

Courier versus Royal Mail ¶

For hazardous materials, Royal Mail has restrictions on what can be sent. Check the current prohibited items list before posting. For anything classified as a dangerous good under ADR, use a courier with appropriate hazmat handling. If you are unsure of the classification, ask before posting.

For non-hazardous samples, standard tracked post is fine. Use a service that provides a tracking number and keep it until you have confirmation the sample arrived.

If you are ever unsure about packaging, email a description of the material before you post it. A five-minute check saves a wasted submission.