Rapid detection of heavy metal ions based on a novel BMIMPF6-MWCNTs/GCE sensor and square wave voltammetry in actual water samples

A novel electrochemical sensor based on multiwalled carbon nanotubes (MWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) hydrophobic ionic liquid for the rapid detection of Pb²⁺ and Cd²⁺ was developed. In this study, the BMIMPF6-MWCNTs composite, as well as BMIMPF6 and MWCNTs, were characterized using SEM. The electrochemical studies were performed using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The BMIMPF6-MWCNTs/GCE exhibited excellent electrochemical activity. The effect of the pH value of 0.1 M NaAc/HAc buffer, deposition potential, and deposition time was investigated. Under the optimal conditions, the linear range for the modified sensors varies from 5 to 1850 µg L⁻¹ for Pb²⁺ and 22 to 600 µg L⁻¹ for Cd²⁺. The limit of detection (LOD) for Pb²⁺ and Cd²⁺ was 0.9 µg L⁻¹ and 0.5 µg L⁻¹, respectively, and the limit of quantification (LOQ) was 3 µg L⁻¹ for Pb²⁺ and 1.7 µg L⁻¹ for Cd²⁺. Moreover, this method showed excellent anti-interference performance, short analysis time, and practicability for determining Pb²⁺ and Cd²⁺. The electrochemical sensor was able to determine heavy metal ions in actual water samples without complex pretreatment, with acceptable recoveries from 98 to 110.8% for Pb²⁺ and 98.6 to 111.3% for Cd²⁺, demonstrating that the sensor based on BMIMPF6-MWCNTs/GCE can apply for Pb²⁺ and Cd²⁺ quantification.