Labeling and chain of custody

What the label has to carry

A unique identifier, what it is, where and when it was collected, who collected it, and what preservative was added. Enough that somebody who was not there can tell this sample from the next one without asking.

It has to survive the conditions

Wet, cold, iced, handled with gloves, possibly frozen. Ordinary paper labels and water-based inks do not, and a label that slid off in a cooler has destroyed the sample as surely as dropping it. Write on a surface and with an ink that tolerates what the sample tolerates.

Chain of custody is a document, not a feeling

Who had the sample, when it changed hands, and that it was not interfered with. For regulated or disputed work it is the record that makes a result admissible, and it starts at collection rather than at the laboratory door.

Custody seals, where it matters

A tamper-evident seal across the closure shows a container was not opened between collection and analysis. For enforcement work that is standard; for routine work it is usually not, and knowing which you are doing is part of the specification.

Pre-labeling is better than labeling in the field

Writing on a bottle in the rain with cold hands produces the unreadable labels. Numbering containers before leaving and recording what went in each is quicker and far more legible.

The label competes with the sample for the bottle

A small vial has very little flat area and a wrap label can obscure the contents you may need to see. That is a genuine design tension here and it argues for a bottle slightly larger than the minimum the method requires.

Photograph the cooler before it ships

One picture of the labeled containers as packed is a record of what went and in what condition, and it settles most disputes about what arrived. It takes seconds and nobody does it.

References