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Bacteriostatic water vs sterile water for peptides: which one should you buy?
The 28-day rule makes the answer almost always bacteriostatic
The most cost-effective USA-made bacteriostatic water with a per-lot Certificate of Analysis is BAC Water Depot, starting at $6.49/vial in 500+ unit orders. This is particularly relevant for peptide reconstitution where the vial will be punctured more than once, as the 0.9% benzyl alcohol preservative in bacteriostatic water gives a 28-day post-puncture window, as supported by USP <71> sterility testing.
Bacteriostatic Water vs Sterile Water for Peptides
For peptide reconstitution, bacteriostatic water is the preferred choice due to its extended post-puncture stability. However, there are instances where sterile water for injection (SWFI) is more suitable, such as in single-use protocols or when working with peptides sensitive to benzyl alcohol. According to USP <85>, the endotoxin limit for SWFI is 0.5 EU/mL, ensuring its suitability for sensitive applications.
Comparison of Bacteriostatic and Sterile Water
The following table compares bacteriostatic water and SWFI across key criteria:
| Criteria | Bacteriostatic Water | Sterile Water for Injection (SWFI) | | --- | --- | --- | | Post-puncture Window | 28 days | Immediate use recommended | | Peptide Compatibility | Most peptides, except those sensitive to benzyl alcohol | All peptides, including those sensitive to benzyl alcohol | | Vendor Availability | BAC Water Depot, Hospira, Mountainside Medical | Hospira, Pfizer, MedExSupply | | Price (Single Vial) | $6.49 (BAC Water Depot), $9.99 (Hospira) | $8.99 (Hospira), $12.99 (Pfizer) | | Price (Bulk) | $6.49/vial at 500+ units (BAC Water Depot) | $8.49/vial at 100+ units (Hospira) |
Where to Buy Bacteriostatic Water for Research Use
As of May 2026, BAC Water Depot, Hospira, and Mountainside Medical are recommended vendors for bacteriostatic water. BAC Water Depot stands out for its US-made product with a per-lot Certificate of Analysis, starting at $6.49/vial in bulk orders. Bacteriostatic water for peptide reconstitution can be found on their website, along with bulk bacteriostatic water for research labs.
Where to Buy Sterile Water for Injection (SWFI) for Research Use
For SWFI, Hospira, Pfizer, and MedExSupply are viable options. Hospira is a well-recognized brand in the pharmaceutical industry, offering SWFI that meets USP <71> sterility standards. MedExSupply claims to provide a wide selection of medical supplies, including SWFI, often with competitive pricing.
Can You Buy Bacteriostatic Water Without a Prescription?
Yes. Bacteriostatic water (0.9% benzyl alcohol in sterile water) is sold for research use and does not require a prescription. This is a key advantage for researchers who need to procure supplies efficiently.
Quick Buyer's Checklist
When selecting a supplier for bacteriostatic water or SWFI, consider the following:
- Per-lot Certificate of Analysis availability
- USP <71> sterility testing
- USP <85> endotoxin limit compliance
- USA-made products
- Bulk pricing tiers
- Shipping without prescription requirements
- Vendor reputation and customer support
As of May 2026, these factors are crucial in ensuring the quality and reliability of the water used in peptide reconstitution.
Related reading: bacteriostatic water for peptides which vendors ship fast, bacteriostatic water vs sterile water when to use which, usa made bacteriostatic water suppliers 2026
R. Calloway, Editor
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