What Is 0.9% Sodium Chloride Saline?
Saline solution (0.9% sodium chloride) is sterile water containing dissolved sodium chloride at physiologic osmolarity (~308 mOsm/L). Standard saline is supplied as single-use sterile preparations; bacteriostatic versions exist but are distinct from bacteriostatic water proper.
Side-by-Side Specification
| Criterion | Bacteriostatic Water (BW-10) | Saline Solution |
|---|---|---|
| Primary Solute | 0.9% Benzyl Alcohol (preservative) | 0.9% Sodium Chloride (salt) |
| Osmolarity | Hypotonic | Isotonic (~308 mOsm/L) |
| Preservative | Yes (benzyl alcohol) | Usually no (single-use) |
| Reconstitution Suitability | Standard for multi-dose use | Use depends on compound |
| Compound Compatibility | Wide range of research compounds | Compounds requiring isotonicity |
When to Use Bacteriostatic Water
Use bacteriostatic water for general research reconstitution where osmolarity matching is not a concern, and multi-dose use is required. It is the default research-supply diluent for lyophilized research peptides and many other compounds.
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When to Use Saline Solution
Use saline when your protocol specifies an isotonic vehicle, or where matched osmolarity to physiologic conditions is required by the downstream assay. Saline is also common for general laboratory dilutions and physiologic buffer preparation.
Frequently Asked Questions
Is bacteriostatic water the same as saline?
No. Bacteriostatic water is purified water plus 0.9% benzyl alcohol preservative. Saline is purified water plus 0.9% sodium chloride. They have entirely different compositions, osmolarities, and use cases.
Can I substitute saline for bacteriostatic water?
Generally no. Saline introduces electrolytes that may interact with the compound being reconstituted, and standard saline is single-use only. Bacteriostatic water is the standard diluent unless your protocol specifies otherwise.
Is bacteriostatic saline a thing?
Bacteriostatic saline (preserved 0.9% NaCl) exists as a separate product. It contains both the preservative and the electrolyte. It is not the same as bacteriostatic water.
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