Choosing your water

Two diluents come up again and again for reconstitution: bacteriostatic water and sterile water. They are not interchangeable, the difference is a preservative, and that single fact decides how long a reconstituted vial stays usable.

Bacteriostatic water

Bacteriostatic water is sterile water with 0.9% benzyl alcohol added as a preservative. The benzyl alcohol suppresses microbial growth, which is what makes a vial suitable for multi-draw use: it can be accessed repeatedly over several weeks while stored refrigerated, rather than being discarded after a single access.

This is the default choice for most reconstitutions where a vial will be drawn from more than once. Peptide.ST stocks 10 mL bacteriostatic water alongside the catalogue.

Sterile water

Sterile water is preservative-free, pure water that has been sterilised and nothing more. With no benzyl alcohol to hold back microbes, it offers no protection once the vial is opened, so it is treated as single-use: reconstitute, draw what the protocol calls for, and discard any leftover. It is the right choice when a preservative would interfere with the compound or the assay, or when the whole vial is prepared and used at once.

Which should I use?

As a rule of thumb: reach for bacteriostatic water when a vial will be accessed repeatedly over time, and sterile water when the preparation is single-use or a preservative is unwanted.