Validation of an Electrothermal Atomization Atomic Absorption Spectrometry Method for the Determination of Aluminum, Copper, and Lead in Grapes

Abstract

An electrothermal atomization atomic absorption spectrometry method was validated to quantify aluminum, copper, and lead in grapes. The limits of detection were 1.11, 0.19, and 0.35 μg/L for Al, Cu, and Pb, respectively. The linearity ranges under optimized conditions were 1.11−50.0, 0.19−25, and 0.35−50.0 μg/L for Al, Cu, and Pb, respectively. The limits of quantification were 74.0, 12.5, and 11.6 ng/g of dry weight for Al, Cu, and Pb, respectively. For all of the metals, the precision for the instrumental method was lower than 5.4% and for the analytical method, lower than 10%. The accuracy of the method was evaluated by the standard additions method, the recoveries being higher than 90% for all of the concentrations added. An interference study was also carried out in a simulated matrix, and it was verified that the deviations from the expected values were lower than 3.4% for all of the metals. The method was applied to the monitoring of the metals referred to above in 35 samples of grapes obtained in marketplaces and at farmhouses. The metals were quantified in the whole grapes, washed or not, and in the peel and pulp of unwashed grapes. Keywords: Method validation; atomic absorption spectrometry; metal residues; grapes