Metals Determination in Wines by Sequential Injection Analysis With Flame Atomic Absorption Spectrometry

Abstract

This paper describes the application of sequential injection analysis with flame atomic absorption spectrophotometric detection (SIA/FAAS) for the determination of Zn, Mn, Fe, and Cu in Portuguese Verde, Maduro, and Porto wines. The basic configuration of the system allowed the determination of Zn, Mn, Fe, and Cu, the latter in concentrations higher than 0.20 mg/L. Selecting a sample volume of 340 µL allowed the determination of Zn and Mn up to 1.50 and 3.00 mg/L, respectively. The Fe determination was accomplished using 85, 120, and 340 µL sample volumes for Fe contents in the range of 1.50 to 15.00 mg/L, 0.50 - 10.00 mg/L, and 0.25 - 5.00 mg/L, respectively. Wine samples with Cu contents in the 0.20 to 2.00 mg/L range were analyzed with a sample volume of 750 µL. The determination of Cu trace levels was carried out using an heterogeneous-phase pre-concentration unit composed of a commercial cartridge packed with silica C18 coupled to the system. Cu was retained as diethylammonium-N,N-diethyldithiocarbamate chelate. Using about 2 mL of sample allowed determination of Cu between 0.05 and 0.50 mg/L. A comparison of the results obtained by the proposed methodologies and the reference procedures presented relative deviations less than 5%. Repeatability of determinations was always better than 3% (RSD).