Determination of cadmium, chromium and copper in vegetables of the Solanaceae family using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Abstract

Three methods have been developed for the determination of cadmium, chromium and copper in vegetables of the Solanaceae family, such as bell pepper, physalis, eggplant, potato, tomato and red pepper, cultivated in conventional and organic farming systems. The samples were lyophilized, milled and the particle size was controlled using a 200 μm polyester sieve. The determination was established using a high-resolution continuum source graphite furnace atomic absorption spectrometer and direct solid sample analysis. The analytical lines at 228.802 nm, 357.869 nm and 327.396 nm were used for Cd, Cr and Cu, respectively. Pyrolysis and atomization temperatures were optimized for all target elements. The calibration curves were obtained with aqueous standard solutions. The characteristic masses obtained were 0.42 pg, 2.7 pg and 19 pg for Cd, Cr and Cu, respectively. The trueness of the methods was confirmed by the analysis of certified reference materials. The concentrations in the vegetables were between 0.78–300 μg kg⁻¹ for Cd, 0.063–1.05 μg g⁻¹ for Cr and 4.5–18.4 μg g⁻¹ for Cu. Some samples presented analyte concentrations above the maximum permitted by legislation. The proposed methods were accurate, simple, fast and sensitive; only a minimum sample preparation was necessary, reducing considerably the sample manipulation and/or dilution.