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.