Simultaneous determination of nickel and iron in vegetables of Solanaceae family using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

A method has been developed for the simultaneous determination of Ni and Fe in vegetables of the Solanaceae family (bell pepper, tomato, potato, eggplant, physalis, and red pepper) using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis (HR-CS SS-GF AAS). The vegetables were cultivated using both conventional and “organic” farming. The samples were lyophilized, milled, and the particle size was controlled using a 200 μm polyester sieve. The primary absorption line for Ni at 232.003 nm and a secondary line for Fe at 232.036 nm were used throughout the study. Pyrolysis and atomization temperatures for both analytes were 1400 °C and 2500 °C, respectively. The molecular spectrum of SiO appeared during atomization, and it was corrected using a least-squares algorithm. The calibration was carried out with aqueous standard solutions. The characteristic masses for Ni and Fe were 95 pg and 340 pg, respectively. The LODs of Ni and Fe were 0.02 μg g− 1 and 2 μg g− 1, and the LOQs were 0.06 μg g− 1and 6 μg g− 1, respectively. The accuracy of the method was confirmed by analyzing a certified reference material of tomato leaves (SRM NIST 1573a). The concentrations of Fe were different for conventional and organic farming, whereas only one group of organically grown vegetables had higher Ni concentrations than the conventionally grown.