Standardization of nitric oxide aqueous solutions by modified Saltzman method

Area of Science:

• Chemistry
• Biochemistry
• Analytical Chemistry

Background:

• Nitric oxide (NO) is a crucial signaling molecule.
• Accurate quantification of NO solutions is essential for research.
• NO is known to be unstable, particularly in the presence of oxygen.

Purpose of the Study:

• To prepare and standardize aqueous nitric oxide (NO) solutions.
• To investigate the stability of NO in aqueous solutions under aerobic and anaerobic conditions.
• To evaluate the modified Saltzman method for simultaneous quantification of nitrogen oxide species.

Main Methods:

• Preparation of NO aqueous solutions using NO gas saturation and a NO donor (NOC-7).
• Standardization using a modified Saltzman method to measure NO, NO2, NO2-, and NO3-.
• Assessment of NO solution stability by monitoring species concentrations and NO's reaction with carboxy-PTIO under aerobic and anaerobic conditions.

Main Results:

• NO solutions prepared under anaerobic conditions showed initial concentrations of approximately 1.8 mM NO, 0.01 mM NO2, 0.1 mM NO2-, and 0.1 mM NO3-.
• Under aerobic conditions for 10 minutes, NO concentration decreased significantly to 0.05 mM, while NO2- increased to 1.7 mM.
• NO instability in air was confirmed by oxygen consumption and the loss of NO's ability to oxidize carboxy-PTIO.

Conclusions:

• Aqueous nitric oxide (NO) solutions are unstable under aerobic conditions, undergoing rapid conversion to other nitrogen oxide species.
• The modified Saltzman method is a valuable tool for the simultaneous quantification of various nitrogen oxide species, enabling practical standardization of NO solutions.
• Understanding NO solution stability is critical for accurate experimental design and interpretation in biological and chemical research.