Single-walled carbon nanotube-ionic liquid paste electrode for the sensitive voltammetric determination of folic acid

A single-walled carbon nanotube (SWNT) paste coated glassy carbon electrode (GCE) has been prepared by using room temperature ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophosphate, OMIMPF6) as a binder. The electrode (i.e. OMIMPF6–SWNT/GCE) combines the features of carbon nanotube and room temperature ionic liquid. Folic acid (FA) can exhibit a very sensitive anodic peak at 0.75 V (vs SCE) in pH 5.5 phosphate buffer solutions, resulting from the irreversible oxidation of FA. Under the optimized conditions, the peak current is linear to FA concentration over the range of 2.0 × 10−9 to 4.0 × 10−6 M by using differential pulse voltammetry, and the detection limit is 1.0 × 10−9 M (S/N = 3). The OMIMPF6–SWNT/GCE is successfully applied to the determination of FA in real samples.