Voltammetric determination of quercetin at a multi-walled carbon nanotubes paste electrode

Quercetin can effectively accumulate at multi-walled carbon nanotubes-paraffin oil paste electrodes (CNTPE) and cause a sensitive anodic peak at around 0.32 V (vs. SCE) in a 0.10 M phosphate buffer solution (pH=4.0). Under optimized conditions, the anodic peak current is linear to quercetin concentration in the ranges of 2.0 X 10(-9)-1.0 X 10(-7) M and 1.x 0.10(-7) -2.0 X 10(-5) M, and the regression equations are i(p) (mu A)=0.0017+ 0.928c (mu M, r=0.999) and i(p) (mu A)=0.183 +0.0731c (mu M, r=0.995), respectively. This paste electrode can be regenerated by repetitively cycling in a blank solution for about 2 min. A 1.0 x 10(-6) M quercetin solution is measured for 10 times using the same electrode regenerated after every determination, and the relative standard deviation of the peak current is 1.7%. The method has been applied to the determination of quercetin in hydrolysate product of rutin and the recovery is 99.2-102.6%. In comparison with graphite paste electrode, carbon nanotubes-nujol paste electrode and carbon nanotubes casting film modified glassy carbon electrode, the CNTPE gives higher ratio of signal to background current and better defined voltammetric peak. (c) 2006 Elsevier B.V. All rights reserved.