[Frontiers in Bioscience 10, 483--491, January 1, 2005]
NICKEL HEXACYANOFERRATE MODIFIED SCREEN-PRINTED CARBON ELECTRODE FOR SENSITIVE DETECTION OF ASCORBIC ACID AND HYDROGEN PEROXIDE
Jie Lin 1, Dao Min Zhou 2, Samo B. Hocevar 1, Eric T. McAdams 2, and Bozidar Ogorevc 1, Xueji Zhang 1
1Analytical Chemistry Laboratory, National Institute of Chemistry, P.O. Box 660, 1001 Ljubljana, Slovenia, 2 Northern Ireland Bio-Engineering Center (NIBEC), University of Ulster, Jordanstown, NI, BT37 0QB, UK
TABLE OF CONTENTS
Electrochemically modified screen-printed carbon electrode (SPCE) has been prepared by electrodepositing nickel hexacyanoferrate(III) (NiHCF) onto the electrode surface using cyclic voltammetry (CV). The performance of NiHCF-SPCE sensor was characterized and optimized by controlling several operational parameters. The NiHCF film has been proven to remain stable after CV scanning from 0 to +1.0 V vs. Ag/AgCl in the pH range of 3 to 10 and is re-useable. The most favourable supporting electrolyte solution exhibiting the optimum electroanalytical performance of the NiHCF-SPCE sensor was found to be 0.2 mol/L sodium nitrate. The electrochemical response toward ascorbic acid (AA) and H2O2 in 0.2 mol/L sodium nitrate solution was studied by using CV and the results showed that both analytes were electrocatalytically oxidized at approximately +0.4 V, while H2O2 also revealed a reduction signal at -0.8 V vs. Ag/AgCl. The NiHCF-SPCE sensor exhibited highly linear response for AA and H2O2 in the examined concentration range from 5.0x10-5 to 1.5x10-3 mol/L and from 2.0x10-5 to 1.0x10-3 mol/L (at +0.4 V), with the correlation coefficients of 0.999 and 0.998, respectively. The reproducibility of the NiHCF-SPCE sensor was followed for the determination of AA by using four individual electrodes, and the relative standard deviation of CV peak currents varied between 0.9 % and 2.2 %. The proposed NiHCF-SPCE has been shown to be a very attractive electrochemical sensor for AA and H2O2, also in a view of inexpensive mass production of disposable single-use sensors. The NiHCF-SPCE sensor was tested by measuring AA in multivitamin tablets, with recoveries obtained between 94.4 % and 108.2 % (n=5).