Determination of Heavy Metals in Honey by Anodic Stripping Voltammetry at Microelectrodes

A methodology for the determination of Cu, Pb, Cd and Zn by differential pulse anodic stripping voltammetry (DPASV) at Hg microelectrodes in honey samples is proposed. The simultaneous quantification of the four metals in the mineralised matrix is prevented by the formation of Cu–Zn intermetallic species during the deposition step. However, the addition of Ga(III) salt to the measurement solution and the metal deposition at a potential lower than that required for Zn reduction allow the determination of the four metals by two DPASV experiments, consecutively performed on the same sample solution. High levels of repeatability (uncertainty better than 2% for metal concentrations higher than 0.2mg g−1, independent of the kind of metal) and not significantly biased results make the proposed method accurate. The detection limits, computed by following the procedure suggested by IUPAC, do not show any significant differences from one another, allowing the computation of a common value equal to 0.0123mg g−1. Although the complete procedure is optimised for the mineralised honey samples, the possibility to obtain speciation information by a direct stripping analysis in raw honey, i.e. a highly viscous real sample, has also been investigated and is discussed.