Slurry sampling of sediments for direct determination of Cu, Mn, Ni, Sn and Zn by graphite furnace atomic absorption spectrometry

In this study, methodologies were developed for the determination of metals (Cu, Mn, Ni, Sn and Zn) in sediments prepared as slurries, which were maintained homogeneous by the introduction of air supplied by an aquariam pump by GF AAS (Graphite Furnace Atomic Absorption Spectrometry). The optimization of the pyrolysis and atomization temperatures were done through pyrolysis and atomization temperature curves using Ir, Rh, Ru, Zr, W and the condition with non-modifier use for generating each curve. To determine Cu, Mn, Ni, Sn and Zn in sediments by slurries, the sample was first dried, then crushed and sifted in a 65 μm sieve and weighed (~ 0,1 g) directly in the auto-sampler cup of the GF AAS, and finally, a 1 mL mixture of 3% H2O2 and 5% HNO3 was added. The slurry was maintained homogeneous by an air flow created using a simple and inexpensive air pump. The optimized methodologies did not present matrix effects, which allowed for use of aqueous calibration of all the examined slurry metals. The relative standard deviation values of the measurements and their correlation coefficients were sufficient to attest the good precision and linearity for the methodologies. The study for accuracy was conducted using standard reference materials (NIST 1944 and 2709 e NRCC PACS-2 and MESS-3), which were in agreement with the certified values for the analyzed metals. The recovery values were between 80 and 120%. The achieved limits of quantification (LOQ) are in compliance with Brazilian federal legislation.