Carbon nanotube-Web modified electrodes for ultrasensitive detection of organophosphate pesticides

Abstract

A novel carbon nanotube-Web (CNT-Web) modified glassy carbon (GC) electrode is prepared and utilized for ultrasensitive electrochemical detection of methyl parathion (MP) organophosphate pesticide (OP) in aqueous solutions. The electrode was prepared by placing and securing 30 CNT-Web layers onto the GC electrode surface drawn with the aid of an electrical winding device. CNT webs comprise bundles of long (∼450μm) multiwalled CNTs with high degree of alignment, porosity and rigidity. These CNT webs are highly electrocatalytic compared to the bare GC electrode. Due to their hydrophobic nature, electrical conductivity and absence of binders they show high affinity toward the adsorption and electrochemical detection of MP by cyclic and differential pulse voltammetries at trace levels compared to other conventional electrodes. Regeneration of the CNT web surface was possible by chemical methods due to the high stability and strong adhesion of the CNT to the GC electrode surface which did not alter the reproducible measurement of MP (RSD 4.7%, n=10). Operational parameters, including the amount of CNT, incubation time, initial scanning potential and pH of the incubation medium have been optimized. The CNT-Web modified electrode yields well-defined, undistorted and interference free voltammetric response with good linearity in the range of 20–1000nM (R2=0.993), 1–10μM (R2=0.993) and 10–50μM (R2=0.991) reflecting its high surface area. A detection limit of 1nM is estimated based on a signal-to-noise ratio of 3 after incubation for 2min along with an average sensitivity of 1.44μA/μM based on three calibration curves. The detection limit was further improved to 1pM by using 10min adsorption time. This new electrode nano-material will open the doors for the design of miniaturized and highly rigid sensors suitable for operation in harsh environments.