Chapter 1 - Nitric oxide (NO) electrochemical sensors

Abstract

This chapter focuses on nitric oxide (NO) electrochemical sensors. Electrochemical (amperometric) detection of NO is the only available technique sensitive enough to detect relevant concentrations of NO in real time and in vivo and suffers minimally from potential interfering species such as nitrite, nitrate, dopamine, ascorbate, and L-arginine. As NO electrodes can be made on the micro- and nano-scale, these techniques have the advantage of being able to measure NO concentrations in living systems without any significant effects from electrode insertion. The first described electrochemical NO sensor was based on a classical Clark electrode design, where NO was directly oxidized on the working electrode surface. Surface modified NO sensors incorporate an electrode surface that is modified or treated to increase the selectivity of the sensor for NO and promote catalytic oxidation of NO. In most applications detection limit, sensitivity, selectivity and response time are usually the most important requirements. The sensitivity of an NO sensor is directly proportional to the electrode size and surface status, where an electrode with a small surface area will generally have a lower sensitivity compared to the one with a larger surface area. Selectivity is controlled by the voltage applied between the working and reference electrode (poise voltage), and the selective membrane used for coating the sensor. The response time depends on the electrode and the electronics being used to read out the current. Currently NO electrochemical sensors provide the only means to measure NO continuously, accurately and directly within living tissue without significant damage.