Immunoperoxidase techniques: the deleterious effect of sodium azide on the activity of peroxidase conjugates.

The effect of including sodium azide as a bacteriostatic agent in solutions used to dilute antibodies conjugated with the enzyme horseradish peroxidase was examined. An enzyme-linked immunosorbent assay (ELISA) and an immunohistochemical method were used and both techniques demonstrated an inhibitory effect of sodium azide on the activity of the peroxidase conjugates. It is concluded that the use of sodium azide in solutions used to dilute peroxidase conjugates is to be avoided.