Reaction of nitrite with ascorbate and its relation to nitrosamine formation

Area of Science:

• Environmental Chemistry
• Organic Chemistry
• Biochemistry

Background:

• Nitrosamines, such as nitrosomorpholine, are environmental contaminants of concern.
• Ascorbic acid is known to inhibit nitrosamine formation.
• The role of oxygen in ascorbic acid-mediated nitrosamine inhibition is not fully understood.

Purpose of the Study:

• To investigate the effect of oxygen on the inhibition of nitrosomorpholine formation by ascorbic acid.
• To elucidate the reaction mechanisms involved in the presence of oxygen.
• To understand the influence of pH on the reaction kinetics.

Main Methods:

• Studying the nitrosation of morpholine in aqueous solutions.
• Varying the concentration of ascorbic acid and the presence/absence of oxygen.
• Monitoring nitrosomorpholine formation over time.
• Analyzing pH-dependent reaction kinetics.

Main Results:

• The amount of ascorbic acid needed for complete inhibition of nitrosomorpholine formation was dependent on oxygen presence.
• Oxygen may react with nitric oxide to form additional oxidizing equivalents or directly oxidize ascorbate intermediates.
• A pH-dependent induction period was observed and explained by reaction kinetics.

Conclusions:

• Oxygen significantly impacts the efficacy of ascorbic acid as an inhibitor of nitrosomorpholine formation.
• The interplay between nitric oxide, oxygen, and ascorbate intermediates is crucial.
• Reaction kinetics, particularly pH-dependent induction periods, provide insights into the complex mechanisms.