Determination of nitrite based on mediated oxidation at a carbon paste electrode modified with a ruthenium polymer

The use of carbon paste electrodes modified with Ru(bpy)(2)(PVP)(10)Cl]Cl for the mediated detection of nitrite is described. This surface modifier substantially lowers the overpotential for nitrite oxidation, hence permitting its determination at a lower potential. Various electrode characteristics were optimized, including the modifier loading and the monitoring potential, using batch amperometry. Standard calibration curves yielded slopes of 0.30 microA/microM over the linear range 5 x 10(-8)-5 x 10(-4)M nitrite with a detection limit of 3 x 10(-8)M (1.38 ppb) nitrite. The modified electrode response was shown to be relatively stable over a period of 5 days with a signal diminution of 8%. Electrode-to-electrode precision was measured as 11.4%. Flow-injection studies indicated the suitability of this electrode as a detector in flowing streams.