Determination of copper, zinc, selenium, lead and cadmium in potatoes (Solanum tuberosum L ) using potentiometric stripping methods..

Potentiometric stripping analysis was used to determine simultaneously, the content of zinc(II), cadmium(II), lead(II) and copper(II) in potatoes, whereas the concentration of selenium was determined by cathodic stripping potentiometric analysis. Metal cations were extracted from potatoes by hydrogen peroxide/hydrochloric acid treatments. The relative standard deviation of the methods ranged from 2.3 to 4.1% and the detection limits were lower than 2.5 μg kg-1. The results obtained with the proposed methods were compared with those obtained with graphite furnace atomic absorption spectroscopy, a common method for determining metals. The results of the two methods agreed to within 6.1%. Twelve samples of yellow flesh potatoes from different cultivars were analysed. Of all the metals determined, Cu and Zn were the most abundant with concentrations between 0.5 and 4.6 mg kg-1. Selenium was only found in three samples in very low amounts (<0.1 mg kg-1), whilst Pb and Cd concentrations were in the range 0.01-0.27 mg kg-1.