Most commercially available antibodies contain small amounts of preservatives such as sodium azide to prevent microbial growth. However, sodium azide is also toxic to mammalian cells as it inhibits cellular respiration. Actual toxicity varies by cell type with neuronal cells being most sensitive. Toxicity is concentration, time, and temperature dependent. For most cell sorting experiments the health of cells are not impacted because the antibody is diluted and cells are typically incubated on ice for less than one hour.