Teaching laboratories use bacteriostatic water differently from research benches: many hands, small volumes, sessions a week apart, and a budget set before the term starts. The choices that work in a research lab, one large shared vial on a bench, are exactly wrong in a teaching lab. This guide is for the coordinator planning a term.
Why small vials win in teaching labs
- Many users, many punctures. A 30 mL vial shared by twenty students in a session is punctured twenty times by twenty different techniques. A tray of 3 mL vials, one per pair, spreads the punctures and contains any contamination to one vial.
- Sessions a week apart. An opened vial's 28-day window covers about four weekly sessions. A 3 mL vial opened in week one is finished, or discarded, by week four; a 30 mL vial is discarded nearly full.
- Teaching the discipline. Students who date a vial, wipe a stopper and discard on schedule learn the practice they will need later. Small vials make each student responsible for one.
Sizing logic is in choosing a vial size and 3 mL vials.
Estimating a term
- Count sessions that use the product, and student stations per session.
- Decide the vial-to-station ratio: one 3 mL vial per station per session for single-session use, or one per station per four-session block if vials are stored between sessions.
- Multiply out, add 15% for demonstrations, breakage and re-runs, and round up to pack sizes.
Example: 4 sections × 12 stations, 6 sessions using the product, one 3 mL vial per station per session: 288 vials plus 15% ≈ 330, i.e., nine 36-packs. Storing vials between sessions instead reduces this to about a quarter. The calculators and estimating usage cover the arithmetic; pack sizes covers rounding.
Storage between sessions
Opened vials, dated and initialed by the student pair, go back into a labeled tray in a room-temperature cabinet, not the fridge. Unopened stock stays in cartons. At the start of each session the instructor discards any vial past its discard date, undated, or failing a quick inspection. See storage and inspection.
Rules students are given
- Inspect the vial: clear, sealed, labeled. Report anything else.
- Write today's date and your initials on the vial when you first open it.
- Flip off the cap, wipe the stopper with 70% isopropyl alcohol, let it dry.
- New sterile withdrawal device every time. Never leave one in the stopper.
- Draw only what the procedure needs. Never return liquid to the vial.
- Return the vial to the tray. Discard devices in the sharps container.
- This water is for the laboratory exercise only.
Print these on a card in every tray; the SOP template can be adapted for the course manual.
What the product is not for in a teaching lab
Cell culture exercises (benzyl alcohol is cytotoxic to cultured cells) and UV spectrophotometry exercises (benzyl alcohol absorbs near 257 nm). Use preservative-free water for those and teach why. See cell culture and analytical interference.
Budgeting
Cost per station per session is the useful number: vial price divided by sessions per vial. With 3 mL vials at one per station per session, it is simply the per-vial price in the pack size you buy; with storage between sessions it falls proportionally. Institutional purchasing language is in buying for institutional labs; term-sized quantities are quoted through the bulk program.
End of term
Discard all opened vials, reconcile unopened stock against the log, note the lot and expiration of what remains, and adjust next term's order from actual use rather than the estimate. See disposal.
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.