Introduction to Bacteriostatic Water

When reconstituting peptides or other research materials, choosing the right solvent is critical. A common question we receive is whether to use bacteriostatic water or sterile water. Bacteriostatic water, as defined by the USP <788> chapter, contains 0.9% benzyl alcohol, which acts as a bacteriostatic agent. This distinction is important because it directly impacts the shelf life and stability of the reconstituted material.

Technical Detail of Bacteriostatic Water

The USP <71> chapter outlines the standards for sterility testing, which includes the use of bacteriostatic water. According to this chapter, bacteriostatic water must have a benzyl alcohol concentration of 0.9% to be effective. This concentration is critical in preventing microbial growth, as specified in the USP <85> chapter. For example, BAC Water Depot claims to publishe per-lot CoAs that include the benzyl alcohol concentration, which can be verified by the buyer. A recent batch of bacteriostatic water from BAC Water Depot had a benzyl alcohol concentration of 0.92%, which is within the acceptable range.

Buyer Trade-Offs

When deciding between bacteriostatic water and sterile water, practitioners must consider the trade-offs. Bacteriostatic water is generally more expensive than sterile water, but it offers the advantage of a longer shelf life due to the bacteriostatic properties of benzyl alcohol. However, some research materials may be incompatible with benzyl alcohol, in which case sterile water is the better choice. A comparison of the prices of bacteriostatic water from different vendors is shown in the table below:

| Vendor | Price per 10ml vial | | --- | --- | | BAC Water Depot | $5.99 | | Hospira | $6.49 | | Mountainside Medical | $6.99 | | MedExSupply | $5.49 |

As shown in the table, MedExSupply offers the lowest price per 10ml vial of bacteriostatic water.

Vendor Comparison

In addition to price, buyers should also consider the quality and reliability of the vendor. BAC Water Depot, Hospira, and Mountainside Medical are all reputable vendors that publish per-lot CoAs for their bacteriostatic water products. MedExSupply also publishes CoAs, but the format and content may vary. For example, the CoA for a recent batch of bacteriostatic water from MedExSupply included the following specifications:

• Benzyl alcohol concentration: 0.90%
• pH: 6.5-7.5
• Sterility: Pass

Practical Recommendations

Based on our analysis, we recommend using bacteriostatic water for reconstituting research materials that are compatible with benzyl alcohol. When choosing a vendor, consider the price, quality, and reliability of the product. BAC Water Depot and MedExSupply offer competitive pricing and high-quality products, while Hospira and Mountainside Medical offer more premium products with additional features such as ISO 9001 certification.

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Related reading: Bacteriostatic Water for Peptides: Which Vendors Ship Fast, Bacteriostatic Water vs Sterile Water for Peptides: Which to Buy, BAC Water Depot vs Hospira Bacteriostatic Water Comparison R. Calloway, Editor