o-phenylenediamine-modified carbon fiber electrodes for the detection of nitric oxide

Nitric oxide (NO.) sensors were prepared using o-phenylenediamine (o-PD) and Nafion to modify the surface of 30 mu m diameter carbon fiber electrodes, These electrodes were compared with nickel porphyrin-type NO. sensors that have already been described, High-speed chronoamperometry, amperometry, and differential pulse voltammetry were used to compare the performance of sensors modified with various combinations of Nafion, o-PD, or nickel(II) meso-tetrakis(3-methoxy-4-hydroxyphenyl)porphyrin (Ni-TMPP), in order to determine which electrodes had the most sensitivity and selectivity for NO., Our findings showed that electrodes treated with Nafion first, followed by o-PD, were very sensitive to NO., with a detection limit of 35 +/- 7 nM, In addition, o-PD electrodes were also very selective against ascorbate (>600:1), dopamine (>300:1), and nitrite (>900:1). Moreover, in the range of 0-6 mu M NO., o-PD electrodes displayed excellent linearity (R(2) greater than or equal to 0.997), In contrast, Ni-TMPP electrodes (with Nafion) had significantly poorer detection limits (76 +/- 12 nM) and were less selective against dopamine (<5:1) and nitrite(<200:1). Ni-TMPP electrodes were also less linear than o-PD electrodes (R(2) greater than or equal to 0.911), Finally, we tested the in vitro and in vivo performance of the o-PD electrode in terms of its ability to detect NO. release from isolated rat renal arterioles and to measure NO. diffusion in the extracellular space of the rat brain.