Technique	NITRATE REDUCTION ,(/,)/,(
Principle	Nitrate may be reduced to nitrite, hyponitrite,hydroxylamine, ammonia, nitrous oxide or gaseous nitrogen. Nitrate reduction is demonstrated by detection of one of the breakdown products, usually nitrite and by the disappearance of nitrate from the medium. The test may be negative because the nitrate has been reduced to some other product. Therefore, zinc dust is added if the nitrite test is negative. If nitrate was not reduced by the bacteria, it will be available for reduction by the zinc and the medium will turn pink.
Cautions	If the nitrate was reduced to a different product, the medium will remain colourless after the addition of the zinc dust.
Method	One ml of nitrate broth is heated at 37 degrees C, inoculated with a heavy suspension of bacteria, and incubated for 15 min at 37 C. Aadd 3 drops of sulphanilic acid and 3 drops of alpha naphthylamine
Results	The appearance of a pink colour within 5 minutes of the addition of sulphanilic acid and alpha naphthylamine indicates the presence of nitrite.
Positive control
Negative control
Reagents
Reference