Prevent antibody contamination with sodium azide

Prepare 20% sodium azide

Add 1 g sodium azide into 5 ml water. Store at room temperature.

Add a final concentration of 0.02%-0.05% sodium azide. (Add 1 – 2.5 ul per ml)

Or

Prepare 1M sodium azide

Add 0.65 g sodium azide into 10 ml water.

Add a final concentration of 5mM sodium azide. (Add 5 ul per ml)

 

Notes:

• Sodium azide is highly toxic by inhalation, ingestion, or skin absorption. Labeled the stock solutions clearly.
• Sodium azide is a preservative used for inhibiting the growth of contaminants such as bacteria or fungi in antibody solutions. However, its presence in antibody solutions can affect the use of the antibody in cell culture assays as it is toxic to cells. It can also interfere with antibody conjugation and also inhibits the activity of the enzyme horseradish peroxidase.
• Sodium azide will inhibit horseradish peroxidase, which is the typical coupled component in secondary antibodies that you detect by chemiluminescence. You would wash the blot at least 3 times after incubating with the preserved primary antibody, therefore no need to be worry. Just remember NOT to preserve your HRP-secondary with sodium azide.
• Sodium azide molecular weight = 65. Thus,

5 mM sodium azide = 0.325 g per liter = 0.0325%

0.02% sodium azide = 0.2 g per liter = 3.1 mM

0.05% sodium azide = 0.5 g per liter = 7.7 mM

 

When NOT to use sodium azide:

If staining or treating live cells with antibodies, or if using antibodies for in vivo studies, be sure to use preparations that do not contain sodium azide. This antimicrobial agent is toxic to most other organisms as well: it blocks the cytochrome electron transport system.

Sodium azide will interfere with any conjugation that involves an amine group, and should be removed before proceeding with the conjugation. After conjugation, antibodies can be stored in sodium azide but 0.01%  thimerosal (merthiolate), which does not have a primary amine, is an acceptable alternative.

http://www.abcam.com/protocols/antibody-storage-guide