Stripping voltammetric determination of trace cadmium and lead in Thai organic unpolished rice after ultrasound-assisted digestion

A cost-effective and environmentally friendly method was developed for the simultaneous determination of trace cadmium and lead contaminants in unpolished rice. An ultrasound-assisted digestion (UAD) procedure was ultilized for sample preparation prior to determination of Cd(II) and Pb(II) by anodic stripping voltammetry (ASV) using an eco-friendly bismuth film electrode (BiFE). The efficiency of the proposed UAD procedure was evaluated by certified reference material of glutinous rice powder. The parameters influencing UAD such as solvent system, sample mass, presonication time and sonication time were evaluated. Using the deposition time of 300 s for ASV, linear calibration graphs in a range of 10-200 mu gL(-1) for Cd(II) and 5-200 mu g L-1 Pb(II) were obtained with detection limits of 0.11 and 0.06 mu gL(-1) for Cd(II) and Pb(II), respectively. Relative standard deviations were 3.5 and 23% for 10 mu gL(-1)of Cd(II) and Pb(II), respectively. The developed system was successfully applied to the analysis of Cd(II) and Pb(II) in various types of organic unpolished rice samples and validated by flame atomic absorption spectrometric method. All studied Thai organic unpolished rice samples were not contaminated with Cd (II) and Pb(II). (C) 2017 Elsevier Inc. All rights reserved.