Electrothermal atomic absorption spectrometric determination of aluminium, cadmium, chromium, copper, iron, manganese, nickel and lead in olive oil

Abstract

A simple and fast procedure for the direct ETAAS determination of Al, Cd, Cr, Cu, Fe, Mn, Ni and Pb in olive oil is proposed.N,N-Hexamethylenedithiocarbamic acid, hexamethyleneammonium salt (HMDC-HMA), was used as a universal modifier with two functions: isoformation of the chemical species of the investigated elements, present in olive oil and their thermal stabilisation during the pre-treatment step. Various organic solvents were studied and 1,4-dioxane was found to be the most suitable solvent for oil dilution prior to ETAAS analysis. 1,4-Dioxane improves the decomposition of triglycerides during the pre-treatment step and permits aqueous standard solutions to be used for calibration. Uncoated graphite tubes with platforms are proposed as atomisers for the ETAAS determination of Cd, Cu, Fe, Mn and Fe, and pyrolytic graphite coated graphite tubes with grooves are the most suitable atomisers for Al, Cr and Ni. Instrumental parameters optimised according to pre-treatment and atomisation curves, obtained in the presence of the olive oil matrix and with HMDC-HMA as modifier, are presented. The proposed method permits the determination of 0.1 µg g–1 Fe, 0.05 µg g–1 Ni, 0.02 µg g–1 Al, Cu, Cr and Pb, and 0.01 µg g–1 Cd and Mn with relative standard deviations of about 8–10% for all analytes in this concentration range.