If a laboratory could stock only one size of bacteriostatic water, the 10 mL vial would usually be it. It is large enough that a regularly used bench does not run out mid-week and small enough that most of it is used before the 28-day discard. This page sets out who it suits and where the boundaries are.
The product
Sterile water with 0.9% benzyl alcohol, endotoxins below 0.5 EU/mL, pH 4.5 to 7.0, crimped multi-use vial with flip-off cap, lot and expiration on every label; filled slightly above 10 mL so that 10 mL is withdrawable. Available in 4, 8, 12, 24 and 36 packs.
The bench it suits
Roughly 3 to 10 mL drawn in 28 days, which is 0.1 to 0.35 mL per day on average, or 0.5 to 1 mL three to five times a week. That profile describes a large share of research benches: regular preparation of small working volumes, several times a week, from one vial that lasts about a month.
Where the boundaries are
- Below 3 mL a month: a 10 mL vial is discarded more than two-thirds full. Step down to 3 mL.
- Above 10 mL a month: a 10 mL vial runs out before the discard date and a second is opened; if that pattern is stable, 30 mL is cheaper per mL used. If usage is lumpy, two 10 mL vials may still be the better choice, because the second is opened only when needed.
- Many small withdrawals: at 0.1 mL per entry, a 10 mL vial takes 100 punctures. Consider 3 mL vials to limit punctures per stopper even if the monthly volume fits a 10 mL.
Economics
The 10 mL vial's cost per millilitre sits between the 3 mL and 30 mL sizes. Its advantage is that the per-mL-used figure is usually close to the per-mL-bought figure, because the typical bench finishes it. A 30 mL vial has a lower sticker price per mL but, discarded half-full, costs more per mL used than a 10 mL vial that was emptied. Run the numbers with the calculators; the reasoning is in what determines the cost per vial.
Handling
Standard practice: inspect before use, date on first puncture, wipe the stopper, new sterile device for every entry, discard at 28 days, carton storage at room temperature. See storage and handling and inspection.
Ordering
For a bench that finishes one 10 mL vial a month, a 12-pack is a year of supply for one bench or a quarter for four benches. Buy so that the last vial in the pack is opened at least six months before its expiration date; the printed date usually gives two years or more, so a quarterly or semi-annual order is comfortable. The procurement checklist covers multi-bench sizing.
Related: 3 mL vs 10 mL vs 30 mL.
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.