A novel electrochemical sensor based on a mixed diazonium/PEDOT surface functionalization for the simultaneous assay of ascorbic and uric acids. Towards an improvement in amperometric response stability
Résumé
A new electrochemical sensor was developed for the simultaneous assay of 2 major antioxidants, namely ascorbic (AA) and uric (UA) acids in neutral media. The electrode was modified by means of electropolymerized conductive poly(3,4-ethylenedioxythiophene) (PEDOT) organic films. The stability of the resulting interface was improved thanks to a thiophene-containing diazonium layer previously grafted onto the glassy carbon substrate. The morphology and electrochemical properties of all PEDOT and diazonium/PEDOT layers were characterized by Field Emission Gun Scanning Electron Microscopy and cyclic voltammetry (CV). The best analytical performances were obtained for both biomarkers with diazonium electrodeposited under galvanostatic mode and PEDOT generated by CV. Using CV the sensitivities and detection limits were found to be 0.345 µA cm-2 µM-1 and 6 µM for AA and 0.665 µA cm-2 µM-1 and 1.5 µM for UA. The calibration curves were linear in the concentration range 12 - 1400 µM and 10 - 1000 µM for AA and UA, respectively. A high selectivity was observed with a detection potential difference more than 250 mV. The sensor exhibited a particularly long lifetime as well in storage (at least 85 % of the initial response recorded after one month) as in operational conditions (more than 80 % recovery after 40 successive measurements).
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