Bacteriostatic Water (BAC Water)

Sterile water containing approximately 0.9% benzyl alcohol as a preservative, supplied for laboratory reconstitution work. The preservative is the entire difference from plain sterile water, and it exists for one specific purpose: it allows a container to be entered more than once without organisms introduced at each entry establishing a population.

Benzyl alcohol is bacteriostatic rather than bactericidal — it inhibits multiplication rather than killing an established population. It does not sterilise a contaminated solution and it does not compensate for poor technique.

What it does not do

It has no effect on the chemical stability of a dissolved peptide. Oxidation, deamidation, hydrolysis and aggregation all proceed at the same rate as they would in plain water; those routes are governed by temperature, pH, concentration and sequence. A reconstituted stock in bacteriostatic water still has the same chemical working life it would otherwise have.

Two further considerations: benzyl alcohol absorbs in the UV and will appear as a peak if reconstituted material is re-analysed by HPLC, and it has measurable effects on membrane fluidity, so carried-over concentration should be calculated rather than assumed negligible where a stock is diluted into a cell-based system. Bacteriostatic water explained covers both in full, including when preservative-free water is the better choice.

Presentation

3 ml, USP grade, SKU BACW3. Water: CAS 7732-18-5, molecular weight 18.02. Store at room temperature; the multi-use window runs from first puncture rather than from purchase, so it is worth recording that date on the vial.

Related: acetic acid for sequences that will not dissolve in neutral water, and the reconstitution guide.

Research use only. Supplied for in-vitro research and laboratory use. Not for human or veterinary use, not a medicine, and not for food or cosmetic application. See the compliance page for the framework NMChem operates under.