The 3 mL vial is the smallest size bacteriostatic water comes in, and it is the size most often bought for the wrong reason (it looks cheap) or skipped for the wrong reason (it looks expensive per millilitre). It is the right choice for a specific kind of bench. This page describes that bench.
The product
Same formulation as every other size: sterile water with 0.9% benzyl alcohol, endotoxins below 0.5 EU/mL, pH 4.5 to 7.0, in a crimped multi-use vial with a flip-off cap, labeled with lot and expiration. Fill is slightly above 3 mL so that 3 mL can be withdrawn; see fill volume and overfill. Sold in 4, 8, 12, 24 and 36 packs.
Who it is for
- Low-volume benches. Any workstation drawing less than about 3 mL in 28 days. A bench that uses 0.2 mL twice a week uses 1.6 mL a month; a 10 mL vial would be discarded 84% full.
- Many workstations. Where each of several benches needs its own vial, small vials keep each on its own sealed supply rather than sharing one large vial across the room.
- Single-lot projects. A short study can be run entirely on one small pack from one lot, with nothing left over for other work to consume.
- Minimum stopper punctures. A 3 mL vial drawn at 0.2 mL is entered about fifteen times; a 30 mL vial at the same withdrawal would be entered 150 times. Fewer punctures mean less coring and less contamination opportunity; see how vials are sealed.
- Infrequent use. A bench that needs sterile water occasionally is better served by opening a small vial when needed than by keeping a large opened vial past its discard date.
Who it is not for
Any bench drawing more than 3 mL a month. Above that, the per-mL premium of the 3 mL size buys nothing, and the 10 mL or 30 mL vial is cheaper in use. The arithmetic is in choosing a vial size and the calculators.
Cost per millilitre, honestly
Per millilitre, the 3 mL vial is the most expensive size, because vial, stopper, crimp, filling and testing cost nearly the same regardless of fill. Per millilitre used, it is often the cheapest, because nothing is thrown away. Compare on the second basis. See what determines the cost per vial.
Handling notes specific to small vials
- Label space is small; write the first-puncture date on a flag of lab tape if the label is full.
- Withdraw with the vial upright until the final entry; inverting a nearly empty small vial gains little.
- Store in the tray. Loose 3 mL vials roll and get lost in drawers.
Ordering
Estimate 28-day consumption per bench, count benches, and buy two to three months of vials in the largest pack size that keeps every vial well inside its expiration date. For a lab of six low-volume benches, that is typically a 24- or 36-pack per quarter. Larger recurring volumes go through the bulk program.
Related: 10 mL vials, 30 mL vials.
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.