Preparation of 50 mg/ml Gentamicin Stock Solution


Gentamicin is an aminoglycoside antibiotic. It is effective against a wide variety of aerobic bacteria including E. coli. A 50 mg/ml stock solution of gentamicin can be prepared by dissolving 50 mg in 1 ml deionized water. Solution is sterilized by filtering through 0.2 µ filter unit.


Gentamicin sulfate salt (e.g., Sigma-Aldrich #G1264)
Deionized / Milli-Q water 

Equipment and disposables 
Falcon® screw cap graduated Conical Tubes, 15 mL (e.g., SARSTEDT, 62.554.502)
Syringe filter unit, 0.2 µ (e.g., SARSTEDT, 83.1826.001)

50 mg/ml gentamicin in water

Preparation of 10 ml of 50 mg/ml gentamicin solution


Use personal protective equipment (lab coat, gloves, goggles, etc) for your safety and follow the guidelines of your institute.

Step 1: Weigh out 500 mg Gentamicin sulfate salt and transfer to a 15 ml Falcon conical tube. Add 8 ml deionized / Milli-Q water. Tighten the cap and dissolve gentamicin by inverting the tube several times. 

Note: Gentamicin sulfate salt dissolves quickly in water. Generally inverting the tube a few times is sufficient to dissolve Gentamicin sulfate salt. Alternatively, one can use a tube rotator to dissolve it. 

Step 2: Adjust the volume 10 ml with deionized / Milli-Q water. Mix by inverting the tube a few times. 

Step 3: Sterilize the solution by filtering through a filter unit containing 0.2 µ filter paper. 

Note: Filter sterilization removes all suspended particles with a size of more than 0.22 μ which includes most bacteria and their spores but not mycoplasma. However, it does not inactivate enzymatic activities (e.g., DNases).

The solution can be stored at -20 °C for several months in small aliquots (0.5 ml or 1.0 ml).

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