Any solution prepared in a laboratory should be traceable back to the lot of every component that went into it, and the diluent is a component. For a solution made with bacteriostatic water, that means the label on the container and the entry in the preparation record both identify the bacteriostatic water lot. This guide sets out a minimum label and a minimum record; a laboratory’s own quality system may require more.
The label
- Material name or identifier.
- Concentration, with units.
- Diluent: “bacteriostatic water, 0.9% benzyl alcohol” and the lot number from the vial.
- Date prepared and discard date.
- Preparer’s initials.
- Storage condition (for example “20–25 °C, protect from light”).
- Any hazard information the laboratory’s chemical hygiene plan requires for the material.
Small tubes that cannot carry all of this are labeled with a preparation ID that points to the full record. Labels are written before or immediately after the solution is made, never from memory later. See how to label the water vials themselves.
The preparation record
| Field | Example |
|---|---|
| Preparation ID | 2026-09-28-01 |
| Material and lot | Reference material XYZ, lot 4471 |
| Amount of material | 5.02 mg (balance ID B-03) |
| Diluent, lot and date the vial was opened | Bacteriostatic water 10 mL, lot 21A0455, opened 2026-09-28 |
| Volume of diluent | 5.00 mL (pipette ID P-11) |
| Final concentration and calculation | 1.00 mg/mL (5.02 mg ÷ 5.00 mL, rounded) |
| Prepared by / checked by | AB / CD |
| Storage location | Reagent cabinet 2, shelf 1 |
| Discard date and disposal record | 2026-10-26; disposed 2026-10-26, AB |
Why the diluent lot matters
If a supplier issues a notice about a lot, or a receiving inspection finds a problem with one, the laboratory has to be able to find every preparation that used that lot. That search is only possible if the diluent lot was recorded at the time. Keeping the certificate of analysis on file for each lot closes the loop: the record points to the lot, and the lot points to its test results. See lot numbers and traceability and how to read a COA.
Paper or electronic
Either works, provided the record is attributable to a person, legible, made at the time of the work, original (or a verified copy) and accurate, the ALCOA principles used in regulated laboratories. Corrections are made with a single line through the original entry, the correction, the date and initials; entries are never erased or overwritten.
Related
SOP template: receiving, storage, use and disposal · Dissolving lyophilized research materials · Preparing a dilution series
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.