Desenvolvimento de metodologias espectrométricas para determinação de metais em água, sedimento e peixe empregando suspensões e solubilização alcalina

Abstract

In this study methodologies were developed to determine metals in water employing ICP OES ICP OES (Optical Emission Spectrometry with Inductively Coupled Plasma) and in sediment and fish employing GF AAS (Atomic Absorption Spectrometry with Graphite Furnace). By ICP OES were determined simultaneously: Ag, Al, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, V and Zn in tap water and spring water. Factorial design was employed to get the full robust working condition of ICP OES. Methodologies for determination of metals in sediment and fish were developed employing permanent modifier for GF AAS. For sediments, the optimization was done by pyrolysis and atomization curves and for fish the optimization was done by factorial design and central composite design (CCD). It was determined Cu, Mn, Ni, Sn and Zn in sediments in slurry. The slurry was prepared using a dry sample, crushed and homogenized (ensuring particle size < 65 ìm) and a mixture of HO 3% v / v HNO 5% v / v. The 223slurry was kept homogeneous by means of air flow created by an aquarium pump. The percentage relative standard deviations in the determination of metals in slurries of sediments were always lower than 10%. It was determined Cd, Mn, Ni, Pb and Zn in fish after solubilization with tetra methyl ammonium hydroxide (TMAH) and Universol. The solutions of reagents were added on the samples of ®fish and kept in a water bath at 60 °C for 30 minutes. The solubilization of the sample of fish with the reagent Universol was completed before TMAH. None of ®the methods, either by ICP OES and GF AAS, presented matrix effect, enabling the use of aqueous calibration, except for the determination of Fe in spring water and Mn in fish. The values of correlation coefficients of calibration curves were always greater than 0.99 showing good linearity of the methodologies. Studies of accuracy were made with certified reference materials or spiked samples. The recoveries were between 80 and 120% for spiked samples of water. To sample the sediment NRCC PACS-2, the result and certificate for Sn, were equal to 19.1 ± 2.8 and 19.8 ± 2.5 mg kg, respectively. To assess the accuracy of the methodology -1for determination of metals in fish, we used the NRCC TORT-2 sample, the results found and certified for Cd, were equal to 21.5 ± 0.8 and 26.7 ± 0.6 mg kg, -1respectively. The limits of quantification (LOQ) obtained were adequate to the requirements of Brazilian legislation. For Cu in sediments could be the value of LOQ equal to 20.5 mg kg-1 and the maximum amount permitted by legislation equal to 400 mg kg. For Cd in fish, the value of LOQ was equal to 52.1 mg kg -1-1and the maximum allowed value of legislation equal to 1000 mg kg.-1