A marker pen and a lot of trust
A soil sample arrives and is registered. In preparation, it is split: a portion for metals, a portion for organics, a portion kept as retained. Each portion is labelled with a marker pen, using the sample ID written a bit shorter because the tube is small. Metals digests it, producing an extract. Organics dilutes theirs. Each step creates new containers with more handwriting.
Almost always, it works. When it does not, a result is attributed to the wrong sample, and finding out how takes an investigation.
Why sub-samples get mixed up
- Only the original sample has a printed label.
- Sub-samples are labelled by hand with shortened IDs.
- The link between parent and child is on a bench sheet.
- Racks and positions are recorded inconsistently.
- Nothing checks the right tube is loaded on the instrument.
Busy periods make it worse. When preparation runs behind, staff work faster, tubes sit in racks waiting for instruments, and the chance of two similar handwritten IDs being confused rises. The process relies on care at exactly the moment care is hardest to give.
What it costs
Mix-ups cause wrong results, amended reports and investigations. Staff spend time writing labels and checking them. Traceability from a result back to the original sample relies on paper.
| Step | Handwritten | Parent-child tracking |
|---|---|---|
| Split | Marker pen labels | Printed labels for each sub-sample |
| Link to parent | Bench sheet | Recorded automatically |
| Extracts and dilutions | More handwriting | New child labels with the chain recorded |
| Instrument loading | Checked by eye | Scanned against the sequence |
| Traceability | Paper | Result to original sample in one view |
The investigation after a suspected mix-up is often the biggest cost. Analysts pull bench sheets, check handwriting, compare instrument sequences and rerun retained portions. Even when it turns out there was no mix-up, the time is spent, and the report to the client may be delayed while the lab makes sure.
How we build it
- When a sample is split, the analyst chooses the sub-samples needed and labels print with unique barcodes, sized for the containers you use.
- Each label links to its parent, and each extract or dilution creates a further child with its preparation details.
- Rack positions are recorded by scanning.
- When loading an instrument, tubes are scanned against the sequence, and mismatches are flagged.
- Results for a child are linked back to the original sample in the LIMS.
- Anyone can scan a tube to see what it is, its parent and its history.
Labels are designed with your team so they are readable on the containers you use, including small vials and freezer tubes, and carry enough human-readable information for a quick visual check alongside the barcode.
What changes
No more marker pens for sample IDs. Links between samples and sub-samples are recorded automatically. Instrument sequences are checked by scan. Investigations can trace the chain from the record rather than from bench sheets.
Retained portions are linked to their parent too, so a retest request leads straight to the right tube. Investigations that used to need a day of bench sheet reading can often be answered from the tube history.
Is this your bench?
- Sub-samples are labelled by hand.
- Parent-child links are on bench sheets.
- Mix-ups have led to amended reports.
- Instrument sequences are checked by eye.
- Tracing a result back to the original sample takes time.