Dual electrochemical microsensor for simultaneous measurements of nitric oxide and oxygen: Fabrication and characterization

A planar-type amperometric dual microsensor was developed for the simultaneous measurement of the nitric oxide (NO) and oxygen (O-2) concentrations. The sensor (overall diameter = similar to 500 mu m) consisted of a dual working electrode (WE) containing two platinized platinum microdisks (25 mu m diameter, WE1, WE2, distance between two disks > similar to 330 mu m) and a Ag/AgCl wire reference electrode covered with an expanded poly(tetrafluoroethylene) gas-permeable membrane. The differentiation and concurrent measurements of NO and O-2 were obtained successfully using two sensing WEs with different applied potentials (+0.75 V for WE1 and -0.4 V for WE2). Cross-talk between WE1 and WE2 was eliminated with an optimized internal solution composition. Linear dynamic range, selectivity, sensitivity, detection limit (<5 nM for NO; <500 nM for O-2), and stability (>50 h) were evaluated. (C) 2009 Elsevier B.V. All rights reserved.