How do you keep chain of custody for plant trial sampling?

This guide covers samples drawn during on-site trials of industrial chemicals, such as lubricants, coolants, water treatment and cleaners, and sent to an in-house or outside lab. It does not replace custody rules for enforcement, forensic or clinical samples, where ASTM D4840 notes legal counsel may be needed to judge what is sufficient.

How do you set up chain of custody for plant trial samples, step by step?

Chain of custody for plant trial samples takes five steps, and each one is written into the trial plan before the first sample is drawn. ASTM D4840, a guide written for water analysis, describes custody procedures as documenting sample possession during collection, shipment, storage and analysis (ASTM, 2018). The same stages exist in a lubricant, coolant or water treatment trial, so the guide's elements apply here as practice, not as a requirement.

1. Assign unique IDs in the trial plan. List every planned trial sample, control and retained split with its ID, sampling point, date and test, and never reuse an ID within the trial. EPA New England's procedure determines the quantity and types of samples and the locations before field work, to the extent possible (EPA New England, 2002).

2. Label at collection. Label the container before or immediately after filling, in waterproof ink, and follow the product SDS and the site's permit for that sampling point.

3. Take the control samples with the trial samples. Draw the baseline or untreated-line sample on the same day, with the same method and from the same point type.

4. Record every handoff. The person relinquishing and the person receiving sign, date and note the time on the custody record (EPA New England, 2002).

5. Seal and ship. Seal the shipping container so tampering shows, keep the courier receipt, and comply with the applicable transport rules, such as US Department of Transportation regulations in the United States (California SWRCB, 2010).

What should a trial sample label carry?

A trial sample label should carry a unique sample ID, the trial and sampling point, date and time, sampler, the tests requested, and whether the sample is a trial, control or retained split. EPA New England lists the required identifying information as a unique field sample number, the parameters to be analyzed and preservation, date and time of collection, station number or location, and samplers (EPA New England, 2002). The California State Water Resources Control Board (SWRCB) guidance adds the serial number on seals and transportation cases to the field record (California SWRCB, 2010).

For a plant trial, two fields matter more than in routine sampling. The role field, trial, control or retained, stops a lab from reporting a baseline as a treated result. The trial plan reference ties the bottle to the plan that fixed the acceptance criteria. Pre-print labels from the plan's sample list, so the ID on the bottle and the ID in the plan cannot drift apart.

Labs follow the same idea on their side: Australia's Therapeutic Goods Administration (TGA) laboratories, addressing clause 7.4 of ISO/IEC 17025, assign a unique identification number as soon as they obtain custody and use it to link all associated documentation (TGA, 2025). Check the sampling method as well. ASTM D4057-22, the manual sampling practice for petroleum products, excludes hydraulic fluids and electrical insulating oils (ASTM, 2022), so confirm which method fits the fluid before writing it on the label.

Why does a plant trial need control and retained samples?

A plant trial needs control samples because a trial result means little without a comparison drawn under the same conditions, and it needs retained samples because a disputed result can only be rechecked against material that still exists. The NIST/SEMATECH e-Handbook of Statistical Methods describes a comparative experiment as agreeing on a measurement by which competing choices can be compared, generating a sample of data from each alternative and comparing average results (NIST/SEMATECH). In a plant trial, the control is the current product or an untreated line, sampled at the same point type, interval and method as the trial.

Environmental custody practice shows how to build these checks in. EPA New England defines field split samples as two or more subsamples taken from one sample, analyzed by different laboratories or by the same one, and uses them to assess sample handling from field to laboratory and laboratory comparability (EPA New England, 2002). The same procedure uses trip blanks to assess contamination introduced during sample transport (EPA New England, 2002).

For a chemical trial, keep a sealed split of each key trial sample at the site, and a retained sample of the new product lot as delivered. Record in the trial plan where retained samples are stored, how long they are kept and who may open them, so a recheck uses material whose custody is as clear as the original's.

What goes on a chain of custody form for trial samples?

A chain of custody form for trial samples carries the sample list and every transfer: sample IDs, collection date and time, tests requested, sampler, and a signature, date and time from each person who releases and receives custody. EPA New England states that any alternative custody form must at a minimum have a unique field sample number for each sample, the parameter for analysis, collection date and time, sampler and a custody transfer signature area (EPA New England, 2002).

The DOE Santa Susana Field Laboratory procedure adds the laboratory's name and address, the date shipped, the courier and airbill number, matrix and preservative, container type and number, and analyses requested (US DOE, 2012). It also requires that a sample left unattended, or a person who refuses to sign, be documented and explained on the record (US DOE, 2012). Contract Laboratory lists the purpose of each transfer and the location among the minimum elements of a lab's custody form (Contract Laboratory, 2025).

For a plant trial, add two fields to the same form: the trial plan reference and the role of each sample. The lab then receives the control and trial samples on one record, tests them in the same batch where the plan asks for it, and reports them side by side. A separate form for controls invites the two to be tested on different days or by different methods.

How do you check trial sample custody records?

Check trial sample custody records at three points, before shipment, at lab receipt and before results are interpreted, using the same pass and fail rules each time. Contract Laboratory describes a receipt check of packaging, temperature, seals, sample ID consistency, quantity and condition, with any failure documented and the sample rejected or quarantined (Contract Laboratory, 2025). Clause 7.4 of ISO/IEC 17025:2017 covers the handling of test or calibration items in the lab (CALA), but the checks before shipment are the trial owner's job.

The table below checks label, control sample, custody form and transport seal for each trial sample.

The custody form row is the one to read first. One unsigned handoff for a trial sample, left unexplained, means that result can no longer be linked to the bottle that left the line.

What should you do when a trial sample's chain of custody breaks?

When a trial sample's chain of custody breaks and the gap cannot be closed from records, close that trial as a failed trial and rerun it instead of interpreting its results. Contract Laboratory says chain-break indicators such as missing signatures, unrecorded transfers or damaged containers should trigger an internal investigation into the impact on sample integrity and whether re-sampling or corrective action is required (Contract Laboratory, 2025). ASTM D4840 treats custody records as one part of data defensibility and states that custody documentation alone is not sufficient in a legal or regulatory situation (ASTM, 2018).

A plant trial is usually a commercial decision rather than a legal one, but the logic holds: a result that cannot be tied to its bottle cannot carry a decision about a product. Write the rule into the trial plan before sampling starts, so nobody decides it after seeing a good or bad number. Then follow three steps. Record the break, its cause and the fix to the procedure. Keep the affected results in the file, marked as not for interpretation. Open a new trial with new IDs and the same acceptance criteria.

Lubinpla's trial preparation issues a trial plan for your review that ties every sample and control to transport and handoff records, and treats a trial that lost integrity as a failed trial to rerun, not a result to interpret.

Common plant trial sampling mistakes

Most plant trial sampling mistakes come from adding custody steps after sampling has started instead of writing them into the trial plan. Common ones are these:

• Reusing an ID across intervals, such as "Line 2 weekly", so two bottles share one name. EPA New England requires a sample number that cannot be reused for the project (EPA New England, 2002).

• Labeling at the bench instead of at the sampling point, which lets bottles swap before they are named.

• Taking the control on a different day or from a different point type than the trial sample.

• Splitting a sample without a linked child ID. Contract Laboratory lists splits without traceable links as a gap in custody (Contract Laboratory, 2025).

• Leaving samples where others can reach them. EPA New England treats a locked vehicle as controlled access, but not a locked lodging room alone, because of potential custodial access (EPA New England, 2002).

• Shipping without writing the courier's shipping number on the custody record (US DOE, 2012).

• Changing the lab or test method partway through the trial, which breaks the comparison even when custody is intact.