Short answers, with links to the full guides. All answers refer to laboratory use of the product.
Composition
1. What is bacteriostatic water? Sterile, endotoxin-controlled water containing 0.9% (9 mg/mL) benzyl alcohol as a bacteriostatic preservative, sealed in multi-use vials of 30 mL or less. Full guide.
2. What does "bacteriostatic" mean? That the preservative inhibits bacterial growth. It does not kill bacteria (that would be bactericidal) and it does not sterilize a contaminated solution.
3. Why benzyl alcohol, and why 0.9%? It is reliably effective at that concentration, fully soluble, and minimally intrusive. The label must state the agent and its proportion, and each lot is assayed. Full guide.
4. What is the pH? Typically around 5.7; the specification is 4.5 to 7.0. It is unbuffered.
5. Does it contain salt? No. It is solute-free apart from the preservative and is hypotonic. Bacteriostatic saline is a different product with 0.9% sodium chloride. Comparison.
Sterility and testing
6. Is it sterile? Yes, in the sealed vial, verified by a 14-day sterility test on each lot. After the first puncture, sterility depends on handling and the preservative. How the test works.
7. What is the endotoxin limit? Not more than 0.5 EU/mL, tested by the LAL method. Sterility and endotoxin are separate tests because sterilization does not remove endotoxin. Full guide.
8. What should a certificate of analysis show? Lot number, appearance, benzyl alcohol assay, pH, sterility, endotoxins, particulates, with results and an approver. Line by line.
Shelf life and storage
9. How long does it last unopened? Until the printed expiration date, stored at 20 to 25 °C and never frozen. Full guide.
10. How long after opening? The laboratory convention is 28 days after first puncture, regardless of volume remaining. Date the vial when opened.
11. Does it need refrigeration? No. Room temperature is the labeled condition. Refrigeration after opening is acceptable if an SOP requires it, but the vial must not freeze. Full guide.
12. Can it go bad? Yes: contamination after opening, oxidation of the preservative (almond odor), freezing damage or seal failure. Discard on cloudiness, color, odor or a damaged seal. Signs.
Vials and sizes
13. Which size should I buy? The one a bench will finish within 28 days of opening: roughly 3 mL for under 0.1 mL/day, 10 mL for up to about 0.35 mL/day, 30 mL above that. Full guide.
14. Why is 30 mL the largest? The pharmacopeial standard limits the container to 30 mL because the preservative is validated for a limited number of entries over a limited time.
15. Glass or plastic? Both are used. Type I borosilicate glass is inert and fully clear; qualified polyolefin is lighter and shatterproof. What matters is a crimped, single-fill sealed vial. Full guide.
Comparisons
16. Bacteriostatic vs. sterile water? Same base water; sterile water has no preservative and is single-use. Use sterile water for cell culture and UV-based analysis. Comparison.
17. Can I use distilled or deionized water instead? No. Neither is sterile, endotoxin-tested or preserved. Distilled, deionized.
18. Can I make it myself? Not in any way a laboratory can rely on: sterility, endotoxin and preservative content cannot be verified at the bench. Why.
Buying
19. How should I compare prices? By cost per millilitre actually used before the 28-day discard, including shipping, not by pack price. Full guide.
20. How do I know a supplier is legitimate? Lot numbers on every vial, a lot-specific COA, crimped seals, a physical address and phone, and direct answers to direct questions. Checklist.
BAC Water Supply stocks 3 mL, 10 mL and 30 mL vials in packs of 4 to 36, ships from the USA, and answers product questions through the contact page. Store policies are on the FAQs page.
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.