What Is Deionized (DI) Water?
Deionized water is water that has had its ions (cations and anions) removed via ion-exchange resins. Resulting water has very low conductivity (~0.055 μS/cm for Type I DI water) but contains no preservative and is generally not sterile unless additionally filtered and processed.
Side-by-Side Specification
| Criterion | Bacteriostatic Water (BW-10) | Deionized Water |
|---|---|---|
| Ion Content | Variable (water + benzyl alcohol) | Near zero |
| Sterility | Sterile (USP <71>) | Not guaranteed sterile |
| Preservative | 0.9% Benzyl Alcohol | None |
| Conductivity | Higher (preservative present) | <0.1 μS/cm typical |
| Use Case | Research compound reconstitution | Buffer prep, glassware rinsing |
When to Use Bacteriostatic Water
Use bacteriostatic water for reconstituting lyophilized research compounds, especially in protocols requiring multi-draw stability.
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When to Use Deionized Water
Use DI water for preparing buffers, rinsing glassware, and laboratory dilutions where ionic purity is critical and sterility is not a downstream concern.
Frequently Asked Questions
Can DI water replace bacteriostatic water?
No. DI water lacks both the sterility verification and the preservative content that bacteriostatic water provides. DI water also has no in-use stability for multi-dose protocols.
Is bacteriostatic water deionized?
Bacteriostatic water is typically produced from purified water (often DI or distilled) that has then been sterilized and preserved with 0.9% benzyl alcohol. The starting water is usually deionized, but the final product is not labeled as DI water.
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