Reagent Labeling: Connecting Stock Solutions, Working Solutions and Analytical Runs
A useful reagent label gives the laboratory an unambiguous way to connect a container with its preparation record and the analytical runs that used it. The source stock, the prepared working solution and the run each have a distinct role. Keep their identities connected so a reviewer can trace a result back to the relevant preparation and supplier lot.
Follow the identity from stock to run
A supplier lot identifies the starting material. A preparation ID identifies the laboratory's particular batch of a stock or working solution. A run record shows which preparation was used for an analytical sequence or batch. A common reagent name, or the supplier lot by itself, cannot distinguish two working solutions made from the same source. When a working solution has more than one relevant input, the preparation record can preserve each source rather than compressing them into one ambiguous label.
Agree which information belongs in each record
The following are example fields to discuss with the laboratory's QA owner. Exact label content and record controls depend on the method and the site's quality and hazard-labeling requirements. The US EPA Laboratory Services Branch quality plan, section 4.23.3.3.4, provides one program-specific example of linking preparation records, purchased stocks, unique IDs and certificates.
| Location | Example information |
|---|---|
| Source stock record | Supplier, catalog or material identity, lot and link to applicable lot documentation. |
| Working preparation record | Unique preparation ID, parent IDs or lots, concentration and units, matrix if relevant, preparation date, method reference and preparer. |
| Container label | Identity and preparation ID with additional fields specified by the site for safe, unambiguous use. |
| Run record | Run or sequence ID and the preparation ID actually used for the relevant reagent or standard. |
Walk through a handoff before ordering or changing stock
Ask the supplier how its lot identifier appears on the container and the lot-specific documentation. Ask the receiving laboratory how it records that identifier and carries it into its preparation system. If two working preparations come from one stock, they can have distinct preparation IDs even when their nominal concentrations match. A later lot investigation can then trace both preparations to the supplier lot and identify which runs used each one.
Where a date is displayed, use the laboratory's defined meaning for that field. A receipt date, preparation date and assigned use-by date describe different events. A supplier's date for the unopened source material does not automatically establish the working solution's use period. Apply the site procedure for any assigned date and keep the supporting basis with the record. The lab's applicable safety labeling is a separate obligation alongside analytical traceability.
Related Reading
- Prepared standards versus in-house preparation. Compare documentation and traceability when deciding which inputs to buy and which solutions to prepare internally.
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