In situ nitric oxide (NO) measurement by modified electrodes: NO labilized by photolysis of metal nitrosyl complexes.

Described are studies directed at refining quantitative analysis of nitric oxide in solution using electrochemical techniques. The fabrication and behavior of several sensors based on modified carbon-based electrodes are reported. This technique has been used to resolve the vexing problem of determining the stoichiometry of the photochemical decomposition of the known antihypertension agent sodium nitroprusside, Na2[Fe(CN)5NO], as well as of two other metal nitrosyl complexes of biological interest, Roussin's black salt, NH4[Fe4S3(NO)7], and Roussin's red salt, Na2[Fe2S2(NO)4], in aqueous solutions. In this manner it was shown that the molar ratios of nitric oxide produced per starting complex photochemically decomposed were 0.95 +/- 0.03, 5.9 +/- 0.2, and 0.50 +/- 0.02 for Na2[Fe(C-N)5NO], NH4[Fe4S3(NO)7], and Na2[Fe2S2(NO)4], respectively.