Clark type NO electrodes

Background currents of all NO electrodes are sensitive to changes of temperature and pH. Depending on type of electrodes, the effect may be more or less. Clark type NO electrodes are very sensitive to temperature change. The temperature induced response... 

For a platinized Pt-based Clark-type NO microsensor (13), the surface of a bare Pt disk electrode is electrochemically platinized by cyclic voltammetry in a platinizing solution (3% chloroplatinic acid in water). As the potential is scanned (from -t-0.6 to -0.35 V vs. Ag/AgCl) using cycUc voltammetry (see Chapter 11), Pt(TV) ions are electroplated on the bare Pt disk electrode to create a porous and roughened electrode surface. The platinized Pt electrode has a larger active surface area as demonstrated by the larger recorded currents and lower detection limits for NO measurements compared with bare Pt electrodes as shown in Figme 6.3.10.1. 

In this Clark-type NO microsensor, a PTFE gas permeable membrane was used for selectivity specific to NO. A capillary structure with the bottom end simply covered with a thin PTFE gas permeable membrane ( 30 pm thick) was used as an outer sleeve of the sensor. A platinized Pt working electrode with a Ag wire reference electrode coiled around its glass sheath was inserted into the outer sleeve filled with an internal solution (aqueous 30 mM NaCl and 0.3 mM HCl solution as recommended by Shibuki) to optimize kinetics of NO oxidation at the platinum working electrode of the NO gas sensor (20). The Pt... 

Using a bare metal, carbon, or porphyrin electrode, it is impossible to differentiate nitrite produced electrochemically than from that derived from chemical NO oxidation. Therefore, a barrier has to be placed between the electrode and the analyte to prevent access of nitrite to the electrode surface. This has been achieved in the porphyrinic sensor by depositing a layer of cation exchanger (Nafion), which repels negatively charged species such as N02 (Fig. 2a). Nafion also prevents the formation of N02 in the film after one electron oxidation of NO to NO" ". In the Clark-type probe, the analyte solution containing NO and nitrite are separated from the inner electrode solution by a gas-permeable membrane. 

Liu X, Liu Q, Gupta E, Zorko N, Brownlee E, Zweier JL (2005) (Quantitative measurements of NO reaction kinetics with a Clark-type electrode. Nitric Oxide 13 68... 

---