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Bacteriostatic water for reconstitution — what it is and how to use it

Reconstituting a lyophilized research material requires a suitable solvent. In laboratory practice bacteriostatic water is the most commonly used. Below we explain what it is, how it differs from other types of water and how to use it.

What bacteriostatic water is

It is water with 0.9% benzyl alcohol added, which inhibits the growth of microorganisms. As a result, a solution prepared from a lyophilizate stays usable longer than with plain water, where the risk of bacterial growth is considerably higher.

Bacteriostatic water versus other types of water

  • Sterile water (WFI type) — sterile, but without a bacteriostatic agent; the solution has to be used much sooner.
  • Distilled water — free of minerals, but neither sterile nor bacteriostatic; not suitable for reconstituting material that is to be stored.
  • Bacteriostatic water — sterile and with an agent that inhibits microbial growth; allows the solution to be stored for roughly 4 weeks when refrigerated.

Reconstitution step by step

The volume of water you add determines the concentration of the solution. For example: 5 mg of material + 2 ml of bacteriostatic water gives a concentration of 2.5 mg/ml. To avoid doing the arithmetic in your head, use the reconstitution calculator.

In practice: add the water slowly down the wall of the vial, do not pour it abruptly onto the centre of the powder and do not shake vigorously — gently swirling the vial lets the material dissolve without damage.

Storing the solution

After reconstitution, store the solution in a refrigerator (2–8°C), away from light. Under these conditions it usually stays usable for about 4 weeks. More on this: how to store peptides.

How much bacteriostatic water to buy

Bacteriostatic water only makes sense in a reasonable quantity — a single vial is rarely enough and does not add up against shipping cost. In our catalogue we offer it in practical sets, with documentation.

Materials for research purposes only. Not for human or animal consumption. We do not advise on use.

Frequently asked questions

How does bacteriostatic water differ from sterile water?
Sterile water is sterile but contains no bacteriostatic agent — the solution has to be used quickly. Bacteriostatic water contains 0.9% benzyl alcohol, which allows the solution to be stored for about 4 weeks when refrigerated.
How much water should I add to the vial?
It depends on the concentration you want. For example, 5 mg + 2 ml gives 2.5 mg/ml. The simplest way is to work it out in the reconstitution calculator.
How long can a solution be stored after reconstitution?
Usually about 4 weeks in a refrigerator (2–8°C), away from light.
For research purposes only. Not for human or animal consumption. This content is scientific and informational (mechanisms and research models) and is not medical advice or usage guidance.
Build a research stack → Reconstitution calculator → Safety data sheets (SDS)

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