Abstract
Vitamin B-9 or folic acid is an important food supplement with wide clinical applications. Due to its importance and its side effects in pregnant women, fast determination of this vitamin is very important. In this study we present a new fast and sensitive voltammetric sensor for the analysis of trace levels of vitamin B-9 using a carbon paste electrode (CPE) modified with 1,3-dipropylimidazolium bromide (1,3-DIBr) as a binder and ZnO/CNTs nanocomposite as a mediator. The electro-oxidation signal of vitamin B-9 at the surface of the 1,3-DIBr/ZnO/CNTs/CPE electrode appeared at 800 mV, which was about 95 mV less positive compared to the corresponding unmodified CPE. The oxidation current of vitamin B-9 by square wave voltammetry (SWV) increased linearly with its concentration in the range of 0.08-650 mu M. The detection limit for vitamin B-9 was 0.05 mu M. Finally, the utility of the new 1,3-DIBr/ZnO/CNTs/CPE electrode was tested in the determination of vitamin B-9 in food and pharmaceutical samples.