Sterile water containing 0.9% benzyl alcohol as a bacteriostatic preservative. For use in reconstituting lyophilised peptides and research compounds in laboratory settings. Supplied in a sealed 10mL multi-dose vial.
Storage conditions: Room temperature, away from direct light
Form: Sterile solution
Bacteriostatic Water UK
out of stock
Free shipping on orders over £75
30 mL orders are supplied as three 10 mL vials from the same lot.
Adults 18+ only. For laboratory research only. Not for use on humans or animals.
Working out volumes? Peptide calculator · Reconstitution guide
BSR-LAB-BAC-2608 · HPLC 99.47%
The batch code matches the vial you will receive. Full analysis — purity, mass spectrometry, residual solvents and microbial limits — is issued with your order.
| Content | 10mL |
| Purity | 99.47% HPLC |
| Form | Sterile solution |
| Storage | Room temperature, away from direct light |
Same-day dispatch — order within
Same-day dispatch before 3pm, Mon–Fri. Next dispatch .
via Royal Mail Tracked 24
Bacteriostatic Water
10mL · £4.99
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative. The preservative is the entire point: it inhibits bacterial growth, which is what allows a single vial to be entered more than once rather than discarded after one withdrawal.
It is the standard diluent for reconstituting lyophilised peptides, and the item most often forgotten when ordering them. BSR supplies it in sealed 10 mL multi-dose vials, dispatched from the UK; a 30 mL order is supplied as three 10 mL vials from the same lot, each with its own seal, which keeps two of the three untouched until they are needed. The volumes involved in peptide work are usually one to three millilitres at a time, so one 10 mL vial reconstitutes several peptide vials.
Bacteriostatic water in the UK: sizes, prices and delivery
BSR holds bacteriostatic water in stock in the UK and posts it by Royal Mail, so an order normally arrives within one or two working days, with no customs charge and no import delay. It can be ordered on its own or with the peptides it is used to reconstitute.
| Size | Supplied as | Price | UK stock |
|---|---|---|---|
| 10mL | One sealed 10 mL multi-dose vial | £4.99 | In stock |
| 30mL | Three sealed 10 mL multi-dose vials from the same lot | £12.99 | In stock |
| UK delivery | Arrives | Cost |
|---|---|---|
| Royal Mail Tracked 48 | Two working days | £3.95, free on orders over £75 |
| Royal Mail Tracked 24 | Next working day | £4.95 |
| Royal Mail Special Delivery | Guaranteed by 1pm next working day · £750 cover | £10.95 |
Orders placed before 3pm Monday to Friday are dispatched the same working day, with the certificate of analysis for the lot. Shipping and returns.
What the preservative does
Benzyl alcohol is bacteriostatic rather than bactericidal: it suppresses the multiplication of organisms introduced on a needle rather than sterilising the contents outright. That distinction is why an entered vial has a usable window measured in weeks rather than an indefinite shelf life, and why aseptic technique still matters when drawing from one.
Benzyl alcohol is not inert. The published literature includes work on its toxicity, and it is the reason preparations containing it are avoided in neonates. It is also not pharmacologically silent around the material it carries — recent work characterises how preservatives of this class interact with peptides in solution, and how far that interaction reverses.
How it is used
Add to a lyophilised vial to bring the material into solution at a chosen working concentration. Let the vial reach room temperature first, direct the water down the inner wall rather than onto the cake, and swirl rather than shake. The volume you add determines the concentration, so it is worth calculating before you start rather than after.
Sterile water is not the same thing. Without the benzyl alcohol preservative it is a single-use diluent, and a vial reconstituted with it should not be entered repeatedly. Sodium chloride solution is a third thing again and is not interchangeable with either.
How much bacteriostatic water per peptide vial
There is no single right volume: the same vial can be made up to different concentrations. These are typical working volumes for the vial masses in this catalogue, with the concentration each gives.
| Peptide vial | Water added | Resulting concentration |
|---|---|---|
| 2 mg | 1 mL | 2 mg/mL (200 mcg per 0.1 mL) |
| 5 mg | 1 mL | 5 mg/mL (500 mcg per 0.1 mL) |
| 5 mg | 2 mL | 2.5 mg/mL (250 mcg per 0.1 mL) |
| 10 mg | 2 mL | 5 mg/mL (500 mcg per 0.1 mL) |
| 20 mg | 2 mL | 10 mg/mL (1 mg per 0.1 mL) |
| 60 mg | 3 mL | 20 mg/mL (2 mg per 0.1 mL) |
A 10 mL vial of bacteriostatic water therefore reconstitutes between three and ten peptide vials, depending on the volumes chosen. Larger peptide vials need more water, not less: a 60 mg vial made up in 1 mL would be too concentrated to measure small volumes from accurately.
Storage and open-vial life
Stored at room temperature, away from direct light — this is one of the few items in the catalogue that does not want a freezer. Unopened, the vial carries the expiry printed on it. Once the stopper has been punctured, the preservative is what permits further withdrawals, but that is not indefinite: the convention for multiple-dose vials, set out in USP General Chapter <797>, is 28 days from first entry unless the manufacturer states otherwise. Write the date of first entry on the label and discard the vial after 28 days, or sooner if the contents are cloudy or discoloured.
Common questions
Where can I buy bacteriostatic water in the UK?
From BSR, on this page. It is held in stock in the UK and dispatched by Royal Mail Tracked 24 the same working day when ordered before 3pm Monday to Friday, on its own or alongside the peptides it is used to reconstitute. Shipping is free on orders over £75. It is supplied for laboratory research use only.
How much does bacteriostatic water cost in the UK?
At BSR: 10mL £4.99, 30mL £12.99. UK delivery is from £3.95 by Royal Mail and free on orders over £75, so it adds nothing to the postage when it is ordered with peptides that take the order over that amount.
How quickly is bacteriostatic water delivered in the UK?
Orders placed before 3pm Monday to Friday are dispatched the same working day from UK stock. Royal Mail Tracked 24 normally arrives the next working day and Tracked 48 within two working days, and both are tracked to the door. Because it is posted from within the UK there is no customs charge or import delay.
Is "bac water" the same as bacteriostatic water?
Yes. Bac water, bacteriostatic water and BW all describe the same thing: sterile water with 0.9% benzyl alcohol as a preservative. It is not the same as sterile water for injection, which has no preservative, or sodium chloride solution.
What is the difference between bacteriostatic water and sterile water?
Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits bacterial growth and allows a vial to be entered multiple times. Sterile water contains no preservative and is intended for a single use. For reconstituting a peptide vial that will be drawn from more than once, bacteriostatic water is the one the protocols specify.
How much bacteriostatic water do I need per vial?
It depends on the concentration your protocol calls for and the mass in the vial — the same 5 mg of peptide can be made up to very different concentrations depending on the volume added. Typical working volumes are 1 mL for a 2 mg or 5 mg vial, 2 mL for a 10 mg or 20 mg vial and 3 mL for a 60 mg vial; the table above gives the concentration each produces. Our peptide calculator converts between vial mass, diluent volume and resulting concentration.
How many peptide vials will one 10 mL vial of bacteriostatic water reconstitute?
Between three and ten, depending on the volume added to each. At 1 mL per peptide vial a 10 mL vial covers ten; at 3 mL per vial it covers three. Most orders of one or two peptides need a single 10 mL vial.
How long does bacteriostatic water last once opened?
The convention for a multiple-dose vial is 28 days from the first time the stopper is punctured, after which it is discarded, whatever the printed expiry. Unopened, the vial is good until the expiry date on the label. Write the date of first entry on the vial.
Does bacteriostatic water need to be refrigerated?
No. It is stored at room temperature, away from direct light. It is one of the few items in this catalogue that does not want a freezer — the lyophilised compounds it is used to reconstitute generally do.
Can bacteriostatic water be used instead of saline?
They are not interchangeable. Sodium chloride solution is isotonic and contains no preservative; bacteriostatic water is neither. Which one a protocol specifies depends on what is being prepared, and substituting one for the other changes both the tonicity and whether the vial can be entered again.
Why is there benzyl alcohol in it?
Benzyl alcohol at 0.9% is the antimicrobial preservative, and it is the only reason a multiple-entry vial is possible. It is bacteriostatic rather than bactericidal — it suppresses the growth of organisms introduced on a needle rather than sterilising the contents.
What sizes does BSR supply?
Sealed 10 mL multi-dose vials. A 30 mL order is supplied as three 10 mL vials from the same lot, so two of the three stay sealed until they are needed, which suits the 28-day open-vial window better than one large vial. Every order is dispatched from the UK with the certificate of analysis for its lot. As with everything on this site it is supplied for laboratory research use and is not for human or animal consumption.
- Xie D. et al. (2025) — Characterization of Peptide-Preservative Interaction and Reversibility by NMR Spectroscopy, Molecular Pharmaceutics
- Maharjan R. et al. (2025) — Effects of antimicrobial preservatives on protein folding stability and subvisible particle formation, European Journal of Pharmaceutics and Biopharmaceutics
- McCloskey S.E. et al. (1986) — Toxicity of benzyl alcohol in adult and neonatal mice, Journal of Pharmaceutical Sciences
Cited as research context. BSR has no involvement in these studies and they do not constitute claims about this product.
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