Selective electrochemical sensor for folic acid at physiological pH using ultrathin electropolymerized film of functionalized thiadiazole modified glassy carbon electrode

This paper demonstrated the selective determination of folic acid (FA) in the presence of important physiological interferents, ascorbic acid (AA) and uric acid (UA) at physiological pH using electropolymerized film of 5-amino-2-mercapto-1,3,4-thiadiazole (p-AMT) modified glassy carbon (GC) electrode. Bare GC electrode fails to determine the concentration of FA in the presence of AA and UA due to the surface fouling caused by the oxidized products of AA and FA. However, the p-AMT film modified electrode not only separates the voltammetric signals of AA, UA and FA with potential differences of 170 and 410 mV between AA-UA and UA-FA, respectively but also shows higher oxidation current for these analytes. The p-AMT film modified electrode displays an excellent selectivity towards the determination of FA even in the presence of 200-fold AA and 100-fold UA. Using amperometric method, we achieved the lowest detection of 75 nM UA and 100 nM each AA and FA. The amperometric current response was increased linearly with increasing FA concentration in the range of 1.0 x 10(-7) -8.0 x 10(-4) M and the detection limit was found to be 2.3 x 10(-10) M (S/N = 3). The practical application of the present modified electrode was successfully demonstrated by determining the concentration of FA in human blood serum samples. (C) 2009 Elsevier B.V. All rights reserved.