McFarland standard solution 0.5

McFarland Standard Solution 0.5 is a turbidity reference solution widely used in microbiology, primarily for standardizing bacterial suspensions before antimicrobial susceptibility testing.

🏭⚗️ Production
McFarland Standard 0.5 is prepared by mixing 0.05 mL of 1% barium chloride with 9.95 mL of 1% sulfuric acid. The reaction produces a fine precipitate of barium sulfate, resulting in a stable, turbid suspension. The solution is mixed thoroughly until uniform turbidity is achieved, transferred into a sealed, clear tube, and stored at room temperature protected from light to preserve its turbidity standard.

🔬 Properties
McFarland Standard 0.5 is a turbid, milky-white suspension that simulates the optical density of a bacterial culture containing approximately 1.5 × 10⁸ CFU/mL. It is chemically stable under normal storage conditions but must be shaken before use to redistribute the precipitate evenly.

🧪 Applications
This standard is commonly used to adjust the turbidity of bacterial suspensions before antimicrobial susceptibility testing, ensuring preparation of inocula with standardized cell density for microbiological procedures.

⚠️ Safety
Handle with care; sulfuric acid is corrosive and barium chloride is toxic. Use gloves and eye protection, work in a well-ventilated area, and avoid ingestion and inhalation. Dispose of any waste according to local chemical safety regulations.