Organizing a Peptide Reagent Inventory: Lots, Labeling, and Rotation

A poorly kept reagent inventory always produces the same symptom: a vial for which nobody knows when it was received, which lot it belongs to, or how long it has been reconstituted. At that point, the data derived from it can no longer be attributed.

The lot log: the base unit

A single table is enough, with one row per physical vial:

• reference and dosage;
• lot number;
• receipt date;
• storage location (freezer / shelf / drawer);
• reconstitution date and solvent, if applicable;
• opening date and operator;
• link to the archived CoA.

A shared spreadsheet does the job perfectly; what matters is that each vial is uniquely identifiable.

A stable labeling convention

A useful label fits in four fields:

REFERENCE — DOSAGE — LOT — DATE

For a reconstituted vial, add the solvent, the final concentration, and the reconstitution date. Use a marker resistant to cold and moisture: a label unreadable after three weeks in the freezer is worthless.

Rotation: FEFO rather than FIFO

The relevant rule is not "first in, first out" (FIFO) but FEFO — *first expired, first out*: the lot whose stability window ends soonest is used first, regardless of arrival date.

In practice: keep the oldest lots at the front of the storage zone, and run a monthly review of lots approaching their documented limit.

Zone the storage

Three distinct physical zones prevent most errors:

1. −20 °C: sealed lyophilizates, long-term stock. 2. 2–8 °C: reconstituted solutions in use, protected from light. 3. Ambient (15–25 °C): consumables, unopened solvents, bacteriostatic water.

A separate quarantine zone is useful for vials awaiting incoming inspection, and a rejection zone for downgraded lots — never mixed with active stock.

Monitoring the cold chain

A min/max thermometer in each cold zone, with a logged weekly reading. In case of a temperature excursion, standard practice is to document the event (duration, temperature reached) and place the affected lots in quarantine rather than returning them to stock untracked.

Archive CoAs with the inventory

The certificate of analysis should be stored with its corresponding inventory row, named after the lot (REF_LOT_CoA.pdf). A CoA that cannot be found when the data is being used is equivalent to an undocumented lot.

To learn more

• Order receipt checklist
• Lyophilized or reconstituted: storage rules
• Traceability and third-party quality control

Research Use Only (RUO). The practices described relate to laboratory reagent management. They imply no use of the products concerned outside laboratory research.