Determination of trace heavy metals in herbs by sequential injection analysis-anodic stripping voltammetry using screen-printed carbon nanotubes electrodes

Abstract

A method for the simultaneous determination of Pb(II), Cd(II), and Zn(II) at low μgL-1 concentration levels by sequential injection analysis-anodic stripping voltammetry (SIA-ASV) using screen-printed carbon nanotubes electrodes (SPCNTE) was developed. A bismuth film was prepared by in situ plating of bismuth on the screen-printed carbon nanotubes electrode. Operational parameters such as ratio of carbon nanotubes to carbon ink, bismuth concentration, deposition time and flow rate during preconcentration step were optimized. Under the optimal conditions, the linear ranges were found to be 2-100μgL-1 for Pb(II) and Cd(II), and 12-100μgL-1 for Zn(II). The limits of detection (Sbl/S=3) were 0.2μgL-1 for Pb(II), 0.8μgL-1 for Cd(II) and 11μgL-1 for Zn(II). The measurement frequency was found to be 10-15stripping cycleh-1. The present method offers high sensitivity and high throughput for on-line monitoring of trace heavy metals. The practical utility of our method was also demonstrated with the determination of Pb(II), Cd(II), and Zn(II) by spiking procedure in herb samples. Our methodology produced results that were correlated with ICP-AES data. Therefore, we propose a method that can be used for the automatic and sensitive evaluation of heavy metals contaminated in herb items. © 2010 Elsevier B.V.