关键词: 微电极, 修饰电极, 亚硝酸根还原

Abstract: The modified powder microelectrode was prepared by etching a Pt (0.1 mm diameter) disk microelectrode and filling in thus formed cavity with Nation_Os(bpy) 3 2+ /PVP composite modified carbon powder. The composite modified powder microelectrode showed cyclic voltammetric behaviors changing with the mole ratio (denoted X) of SO 3 - to Os(bpy) 3 2+ in Nafion. When X=3, a single pair of current peaks appeared near 0.6V (vs. SCE) due to Os(bpy) 3 2+/3+ redox couple. In contrast, for X=20, a pair of additional current peaks occurred near 0.4V. Both X=3 and X=20 modified powder microelectrodes strongly catalyzed the first electron reduction of nitrite in 0.5 mol/L H 2SO 4. The catalysis was so effective that the steady state polarisation curve showed essentially reversible characteristics with a plateau current density 2.18 mA/cm 2 and half_wave potentials near 0.55 V. While the electrode with X=3 could catalyze nitrite reduction only to the first electron transfer, the modified powder microelectrode with X=20 could catalyze the second electron transfer, resulting in an additional current wave starting near 0.4 V with a plateau current twice the first one. The plateau current densities obtained with the composite modified powder microelectrodes were much larger than those obtainable with flat electrodes (with or without modification), verifying the idea of advantageous combination of the composite modification and the porous electrode technique. The composite modified powder microelectrodes showed high performance in nitrite detection: sensitivity 814 mAL/cm 2 mole, linearity 10 _6 ～0.25 mol/L, lower detection limit 10 _6 mol/L; no interference from 0.1 mol/L ascobic acid, Fe 3+ ,Fe 2+ ,Mg 2+ ,K +,NH 4+ ,Cl -,NO - 3 and PO 3_ 4.

Key words: Microelectrode, Modified electrode