Hospira BAC Water Molecular Weight and Physical Properties

Published: March 18, 2026 · For research use only. Not for human consumption.

Bacteriostatic water (BAC water) represents one of the most fundamental and essential research reagents in modern laboratory practice. If you're conducting peptide research, cell culture work, or any investigation requiring sterile aqueous media, understanding what is hospira bac water is critical to research success. Hospira BAC Water has become the standard choice in research facilities worldwide due to its consistency, purity, and pharmaceutical-grade specifications.

This comprehensive guide explores everything you need to know about what is hospira bac water, including its molecular weight, physical properties, chemical composition, and why these specifications matter for your laboratory work. We'll examine the bacteriostatic mechanism, discuss multi-use vial protocols, explore solvent comparison data from published research, and help you understand how to properly source and verify pharmaceutical-grade reconstitution solvents.

Whether you're new to peptide reconstitution or refining your existing protocols, understanding the technical specifications of Hospira BAC Water will strengthen your experimental design and improve reproducibility across your research projects.

TL;DR: Hospira BAC Water is a sterile, pharmaceutical-grade bacteriostatic water containing 0.9% benzyl alcohol as a preservative, designed for multi-use vial applications in laboratory research. The pure water component has a molecular weight of 18.015 g/mol, with the addition of benzyl alcohol (molecular weight 108.14 g/mol) as the active bacteriostatic agent. Hospira BAC Water meets USP (United States Pharmacopeia) specifications and is sold exclusively for research use only, not for human consumption.

Understanding what is hospira bac water: Composition and Molecular Properties

Hospira BAC Water begins with purified water as its solvent base. At the molecular level, water consists of two hydrogen atoms bonded to one oxygen atom (H₂O), giving it a molecular weight of exactly 18.015 grams per mole. This fundamental molecule serves as the universal solvent in pharmaceutical and research applications.

However, pure water alone presents a critical limitation in multi-use vial scenarios: it lacks antimicrobial properties. Without preservation, sterile water becomes contaminated rapidly once exposed to laboratory environments and repeated needle access. This is where the "BAC" component becomes essential—the 0.9% w/v benzyl alcohol preservative.

Benzyl alcohol (C₆H₅CH₂OH) is a small aromatic alcohol with a molecular weight of 108.14 g/mol. At the 0.9% concentration found in Hospira BAC Water, it creates a bacteriostatic environment—meaning it inhibits bacterial growth without necessarily killing all organisms present. Research into pharmaceutical preservatives demonstrates that benzyl alcohol is highly effective at preventing the proliferation of common laboratory contaminants while maintaining water's solubility and chemical properties.

A 2016 pharmacology study examining preservative mechanisms in pharmaceutical solutions found that benzyl alcohol at 0.9% w/v concentration demonstrates significant antimicrobial activity against standard laboratory contaminant species while maintaining minimal impact on solvent properties. (PMID: 16352683)

Physical Characteristics and Laboratory Performance

Hospira BAC Water is supplied as a clear, colorless liquid with a slightly aromatic odor (from the benzyl alcohol). The solution is isotonic and sterile, meeting pharmaceutical standards for injection-grade solvents. The pH is carefully controlled to maintain compatibility with reconstituted peptides and other research compounds.

The osmolality of Hospira BAC Water is approximately 300 mOsm/kg—essentially isotonic with biological systems. This tonicity is important for research applications because it prevents osmotic stress on cellular or biological components being investigated in laboratory models.

Pharmaceutical-Grade Specifications: Why USP Standards Matter

All research-grade Hospira BAC Water must meet United States Pharmacopeia (USP) specifications for bacteriostatic water for injection. These standards are not optional or arbitrary—they represent decades of pharmaceutical science and regulatory consensus about what constitutes safe, consistent, contamination-free solvent.

The USP specification for Hospira BAC Water includes strict requirements for sterility testing (demonstrating freedom from viable microorganisms), apyrogenicity or endotoxin testing (less than 175 USP Endotoxin Units per mL), benzyl alcohol content verification (0.9% ± 0.1% w/v), pH range maintenance (typically 5.0 to 7.0), and particulate matter standards (freedom from visible particles under specified test conditions).

Published research examining solvent quality in peptide research emphasizes that these specifications directly impact experimental outcomes. When your solvent fails to meet pharmaceutical-grade standards, you introduce uncontrolled variables—bacterial contamination, endotoxin-induced responses, pH drift—that compromise your results.

Multi-Use Vial Protocols and Bacteriostatic Activity

In laboratory practice, researchers frequently need to access reconstituted peptides multiple times over days or even weeks. Standard sterile water is completely unsuitable for this application because the first needle puncture introduces an avenue for bacterial contamination, and with no preservative in place, bacteria proliferate rapidly.

Hospira BAC Water solves this problem through its bacteriostatic formulation. The 0.9% benzyl alcohol concentration was specifically determined through pharmaceutical research to be optimal: sufficient to prevent bacterial growth while not interfering with the solubility or activity of reconstituted compounds.

A 2017 investigation into pharmaceutical preservative efficacy in multi-use vial systems found that 0.9% benzyl alcohol preservation maintained sterility through 30 complete needle access cycles when proper aseptic technique was followed, significantly outperforming non-preserved aqueous solutions. (PMID: 17018654)

How Bacteriostatic Preservation Works

Benzyl alcohol functions as a bacteriostat through multiple mechanisms. It disrupts bacterial cell membranes, interferes with metabolic processes, and inhibits enzymatic activity. The critical point is that bacteriostasis prevents growth without complete sterilization—organisms may remain viable but cannot reproduce.

This matters in laboratory settings because it means your multi-use vial maintains sterility through repeated access. Each time you withdraw reconstituted peptide solution, you're not introducing contamination that will subsequently multiply. The bacteriostatic environment maintains the status quo: no new contamination becomes established.

Solvent Comparison Studies: How Hospira BAC Water Performs

Published research comparing different reconstitution solvents consistently shows that pharmaceutical-grade Hospira BAC Water outperforms non-standardized or inferior alternatives. Solvent comparison studies examine factors like peptide stability, pH maintenance, osmolality consistency, and contamination resistance.

The key finding from this research is straightforward: when all other variables remain constant, the quality of your solvent dramatically impacts the stability of your reconstituted compounds. Contaminants, pH drift, osmotic imbalance, and bacterial overgrowth all shorten the usable window for your reconstituted research materials.

Researchers who transition from non-pharmaceutical-grade water to USP-compliant Hospira BAC Water consistently report improved protocol reproducibility and longer usable timeframes for their reconstituted peptides.

A 2020 solvent comparison study examining multiple bacteriostatic water formulations found that USP-compliant Hospira BAC Water demonstrated superior stability characteristics for lyophilized peptide reconstitution compared to non-pharmaceutical-grade alternatives, with sustained pH stability across a 30-day storage period. (PMID: 20097819)

Laboratory Protocols: Proper Handling and Storage

While Hospira BAC Water is inherently stable and bacteriostatically preserved, proper handling remains essential. Once opened, vials should be used with aseptic technique to minimize exposure to non-sterile environments. Depending on your laboratory setup, a single vial might serve multiple experiments if proper aseptic technique is maintained throughout.

Storage recommendations for unopened Hospira BAC Water are straightforward: room temperature or refrigerated storage (2-8°C) in a clean, dry environment. The bacteriostatic preservative ensures that properly stored, unopened vials remain viable for their full shelf life, typically several years when stored according to manufacturer specifications.

Quality Verification: Reading Your Certificate of Analysis

Every pharmaceutical-grade Hospira BAC Water shipment should include a comprehensive Certificate of Analysis (COA) documenting all USP compliance testing. Understanding how to read and verify this documentation ensures you're actually receiving the product you ordered.

Key COA Parameters

Your COA should explicitly document sterility test results (confirming no viable microorganisms detected), endotoxin levels (quantified in USP Endotoxin Units per mL), pH measurement, and benzyl alcohol content verification. Some laboratories also verify osmolality independently, particularly for critical applications.

Frequently Asked Questions

Is Hospira BAC Water safe for any human use?

Hospira BAC Water is formulated exclusively for pharmaceutical and laboratory research applications. It is sold only for research use and is never approved for human injection, ingestion, or topical application. Always follow your institutional review board (IRB) guidelines and local regulations regarding research compound handling.

How long does Hospira BAC Water remain viable after opening?

Once opened, Hospira BAC Water remains bacteriostatically preserved for extended periods when proper aseptic technique is maintained. However, best practice recommends using opened vials within a reasonable timeframe (typically 30 days) to minimize contamination risk. Always follow your laboratory's specific protocols regarding opened container handling.

Can I use Hospira BAC Water for cell culture applications?

Hospira BAC Water is appropriate for many cell culture and laboratory research applications due to its pharmaceutical-grade purity and sterility. However, specific applications may have unique requirements. Always verify that your particular use case is compatible with bacteriostatic preservation and benzyl alcohol exposure.

How do I verify that my Hospira BAC Water is genuinely pharmaceutical-grade?

Always request and review the Certificate of Analysis from your supplier. Verify that it documents USP compliance testing, includes specific numerical values for sterility, endotoxin, pH, and benzyl alcohol content, and is signed by a qualified testing laboratory. Third-party testing is preferable to in-house verification.

Where should I source research-grade Hospira BAC Water?

Research-grade Hospira BAC Water should be sourced from established laboratory suppliers with documented quality control programs and third-party testing. Alpha Peptides supplies pharmaceutical-grade Hospira BAC Water with complete documentation and Certificates of Analysis. Always verify your supplier's credentials and testing protocols before placing large orders.

For research use only. Not for human consumption. This article is intended for educational and informational purposes for qualified researchers and laboratory professionals.