Sequential and simultaneous determination of four elements in soil samples using high-resolution continuum source graphite furnace atomic and molecular absorption spectrometry

Abstract

An analytical method has been developed for the sequential and simultaneous determination of Cd, Cr, Fe and Al (via the AlH molecule) in soil samples using high-resolution continuum source graphite furnace atomic and molecular absorption spectrometry and direct solid sample analysis. First, Cd (228.802 nm) was determined using 800 °C and 1700 °C as the pyrolysis and atomization temperatures, respectively. Subsequently, after changing the wavelength, Cr (425.433 nm), Fe (425.076 nm) and Al (425.315 nm) were determined simultaneously from the same sample aliquot using 2600 °C as the atomization (Cr and Fe) or vaporization (AlH) temperature. Al determination was carried out using the diatomic molecule AlH without adding a molecule-forming reagent. The interference caused by Al in Cd determination was minimized by using 10 μL of a 10% v/v H₂SO₄ solution in all measurements. Aqueous standard solutions were used for calibration and the limits of detection and quantification obtained were 7.3 and 24 pg mg⁻¹ for Cd, 0.13 and 0.45 ng mg⁻¹ for Cr, 0.07 and 0.23 μg mg⁻¹ for Fe and 0.42 and 1.4 μg mg⁻¹ for Al, respectively. The concentration values for Cd, Cr, Fe and Al obtained from the soil certified reference material (CRM) Montana Soil I (NIST SRM 2710a) analysis were in agreement with the reported ones. The precision of the measurements, expressed as the relative standard deviation, was better than 10%. Six soil samples from a vineyard field were investigated and the results are in accordance with the Brazilian legislation.