Product Overview and Composition

Sodium Citrate Buffer (0.1 mol/L, pH 4.5, Sterile) is a ready-to-use aqueous buffer solution prepared from sodium citrate and citric acid at a defined molar ratio to achieve a stable pH of 4.5. The solution is sterile-filtered to minimize the risk of microbial contamination, making it suitable for cell-based assays, enzyme activity studies, and other pH-critical protocols that require a contamination-free environment.

The citrate buffering system is effective in the pH range of approximately 3.0–6.2, and a pH of 4.5 falls within the optimal buffering capacity zone, ensuring reliable pH maintenance throughout typical experimental timescales.

Storage, Handling, and Viscosity Behavior

This buffer should be stored at 2–8°C under refrigerated conditions. An important physicochemical characteristic of this formulation is that it appears viscous at refrigerated temperatures (2–8°C). This is a normal product attribute and does not indicate degradation or contamination.

Before use, allow the buffer to equilibrate to room temperature. The viscosity will resolve, and the solution will return to its normal fluid consistency. Gently mix or invert the container after temperature equilibration to ensure homogeneity before use. Do not heat the solution above room temperature to accelerate equilibration, as this may affect pH stability and sterility.

Once opened, follow standard aseptic technique to preserve sterility. Record the date of opening on the container label. Avoid repeated freeze-thaw cycles unless explicitly validated for your application.

Recommended Applications and Protocol Guidance

Sodium citrate buffer at pH 4.5 is widely employed across several research domains. Typical applications include:

• Antigen retrieval in immunohistochemistry (IHC): Citrate buffer at acidic pH is a standard choice for heat-induced epitope retrieval (HIER), exposing masked antigens in formalin-fixed, paraffin-embedded (FFPE) tissue sections.
• Enzyme activity assays: Many glycosidases and other acid-active enzymes have optimal activity near pH 4.5, making this buffer suitable for substrate incubation and kinetic measurements.
• Cell biology experiments: Sterile citrate buffer at pH 4.5 can be used in controlled acidic microenvironment studies or as a vehicle for reagent dilution where sterility is critical.
• Protein solubility and stability studies: Certain proteins exhibit improved solubility or reduced aggregation at mildly acidic pH, and this buffer provides a reproducible matrix for such investigations.

Always verify that pH 4.5 is compatible with your specific biological targets and downstream detection methods prior to experimental use.

Quality Assurance and Regulatory Considerations

Each lot of Sodium Citrate Buffer (0.1 mol/L, pH 4.5, Sterile) is manufactured and quality-controlled to ensure consistency in concentration, pH, and sterility. The sterile filtration process is designed to remove microbial contaminants, making the product suitable for cell culture-adjacent applications.

Researchers should note that while this product is sterile, it is intended for research use only and is not approved for clinical, diagnostic, or therapeutic use. For GLP or GMP-regulated studies, users should request a Certificate of Analysis (CoA) and retain it with experimental records.

Inspect the solution visually before use. At room temperature, the buffer should appear as a clear, colorless to faintly yellow solution. If turbidity, precipitation, or color changes inconsistent with normal product appearance are observed after equilibration to room temperature, do not use the product and contact Aladdin Scientific technical support.