Electrocatalytic reduction of nitrite at a glassy carbon electrode surfacemodified with palladium(II)-substituted Keggin type heteropolytungstate

A potassium salt of palladium(II)-substituted Keggin type heteropolytungsta te, K-6[(H2O)PdSiW11O39] (abbreviated as PdSiW11 in the following), was use d to fabricate a new kind of chemically modified electrode (CME) by potenti al scanning on the surface of glassy carbon electrode. Characterization of this modified electrode was conducted by Fourier transform infrared reflect ion absorption spectroscopy (FTIRRAS), X-ray photoelectron spectroscopy (XP S) and cyclic voltammetry (CV), FTIRRAS and XPS showed that the species on the electrode surface sustained the same Keggin type structure as that of t he heteropolytungstate in buffer solution. A couple of waves was observed o n the PdSiW11 CME, which was assigned to the redox process of the palladium center in the heteropolytungstate. This CME had high electrocatalytic acti vity towards nitrite reduction and exhibited good reproducibility and stabi lity. The catalytic peak current was found to be linear with the nitrite co ncentration in the range 1-20 mmol/l with a correlation coefficient of 0.99 8, The PdSiW11 CME is successfully applied as an electrochemical detector t o monitor nitrite in flow injection analysis (FIA). The linear range is ove r three orders of magnitude and the detection limit is 24.0 pmol for nitrit e determination. The relative standard deviation (RSD) for ten successive m easurements of 1.0 mmol/l nitrite in FIA is found to be 3.38. (C) 1999 Else vier Science B.V. All rights reserved.