Two water-based solvents appear most frequently in peptide reconstitution documentation: bacteriostatic water and sterile water. Although both are water, they are prepared differently and are referenced in different circumstances.
Sterile water
Sterile water is water that has been processed to remove microorganisms and contains no added preservative. Because it lacks a bacteriostatic agent, documentation typically references it for single-use preparation.
Bacteriostatic water
Bacteriostatic water contains 0.9% benzyl alcohol, an agent that inhibits the growth of bacteria. This property is why it is frequently referenced for preparations that are documented as being drawn from over a period of time. The benzyl alcohol content is the defining difference from plain sterile water.
Practical notes for documentation
- Both solvents are used for the same arithmetic — the concentration equation does not change with solvent choice.
- Solvent selection is a property of the protocol and the peptide's solubility, not a property of the calculation.
- Record which solvent and what volume was used alongside the lot number for reproducibility.