In situ detection of nitric oxide

The measurement of the concentration of nitric oxide (NO) is a challenging problem because of the short half-life of NO (t (1/2)=3-6 s) in biological systems (1). The instrumental techniques used currently for NO measurements are spec-troscopic and electrochemical methods (2). Electrochemical methods offer several features that are not available from analytical spectroscopic methods. Most important is the capability afforded by the use of ultramicroelectrodes for direct in situ measurements of NO in single cells near the source of NO synthesis. NO released from the cell can be detected within a few miliseconds after injection of nitric synthase agonist, and the NO concentration on the membrane surface may vary from submicromolar to micromolar levels (3).