Determination of trace levels of nitric oxide in aqueous solution

Nitric oxide at trace levels (< 10/sup -13/ M) in aqueous solution is determined by using a flow system to equilibrate the solution with a gas stream and measuring NO/sub g/ with a chemiluminescence detector. A standard p/sub NO/ prepared by dynamic dilution of gases is used to calibrate the detector and to test the system for adsorptive and artifact effects. NO signals are differentiated from interferents by criteria based on the gas/solution partition coefficient of NO, its low boiling point, or reversible formation of the Fe(NO)/sup 2 +/ complex. The precision of the technique at the greater than or equal to 10/sup -13/ M(NO)/sub aq/ level is approx. +- 3% and the accuracy is estimated to be +- 20%; a determination requires about 2 min. The versatility of the method and its applicability to environmental measurements are illustrated by relevant examples.