Preparation of 1 mg/ml Biotin Stock Solution in Water


Biotin (also known as vitamin B7) is slightly soluble in water but soluble in hot and alkaline water. A 1 mg/ml Biotin stock solution can be prepared by dissolving 10 mg of Biotin in slightly alkaline water to a final volume of 10 ml. 


Reagents and solutions
Biotin (C10H16N2O3S, Molecular Weight 244.31)
Deionized water

Equipment and disposables
15 ml graduated screw-capped centrifuge tube
Vortexer mixer or Tube Rotator

1mg/ml Biotin


Step 1: To prepare 10 ml of 1 mg/ml biotin stock solution, weigh out 10 mg Biotin and transfer it to a 15 ml graduated screw-capped centrifuge tube. Add 9 ml water and mix by vortexing the tube or by keeping it on the tube rotator. Add a few drops (2 – 3) of 1N NaOH and keep vortexing/rotating the tube. After a few minutes if you still see some undissolved particles floating in the solution, add a few more drops of NaOH and vortex/rotate the tube. Keep repeating this until all Biotin is dissolved. 

Do not dissolve in 10 ml of deionized / Milli-Q water. Volume of the solution will increase when you add a few drops of 1N NaOH to dissolve biotin.

Step 2: Adjust the volume to 10 ml with deionized water. Mix it again.

Step 3: Sterilize the solution by filtering through a syringe filter unit containing a membrane with pore size 0.22 μm or less under aseptic condition.

Aseptically aliquoted the solution into smaller volumes (0.5 ml or 1 ml)  and stored at -20°C until use.

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