Phosphate-Catalyzed Decomposition of Nitrite to Nitrate during Freezing and Thawing of Solutions

A reaction leading to decomposition of nitrite ions to nitrate, catalyzed by phosphate, during freezing-thawing of solutions is reported. Factors such as solution pH, presence of calcium ions, substrate concentration, and temperature and duration of freezing affected the reaction rate. It is postulated that a sharp decrease in the system pH during the freezing process or frozen state, catalyzed by phosphate ions, led to the decomposition of nitrite ions. The results exemplify the potential of major artifacts in research caused by well-accepted laboratory practices such as freezing.