Effects of Freezing on Nitrite Stability in Aqueous Solutions

Abstract

The effects of freezing on nitrite stability in microbial cultures and in other liquid media were examined. Nitrite (12-13 mg (NO2)N/ 100 mL, pH 5.7) in culture and aqueous media was very unstable during frozen storage. Freezing resulted in the degradation of nitrite to other products including nitrate. Losses of 38-57% of the nitrite occurred after 15 days of frozen storage. Neither addition of chloroform nor a 5 min boiling treatment before freezing prevented nitrite destruction. However, nitrite concentration in the unfrozen portion of aqueous media increased during the freezing process. Nitrite can be stabilized during frozen storage by increasing the pH to near 11.0. For aqueous solutions, nitrite can be preserved by the use of chloroform or by increasing the pH to 11.0 and storing at 5°C.