Avaliação de um procedimento de extração sequencial assistida por ultrasom para o fracionamento de metais em amostras de sedimento

Abstract

Sequential extraction procedures are important because they provide useful information on the ecological and biological effects of the species, but require preparation days. This work aimed to develop an alternative sequential extraction methodology using ultrasonic radiation. The BCR method was used as a reference. Were obtained recoveries greater than 90% in the first three fractions for Zn. In Cu extractions, recoveries of over 90% were obtained in the first two fractions and equal to 40% in the third. A condition was not found that would allow the extraction of the analytes simultaneously, applying the BCR protocol to the sediment samples from the Chapéu D’Uvas dam. The total concentration of analytes determined by F AAS ranged from (41 ± 4 to 58 ± 2); (68 ± 12 to 106 ± 8); (48 ± 1 to 116 ± 10) and (46 ± 1 to 98 ± 22) mg kg-1 for the analytes Cu, Cr, Ni and Zn, respectively. Precision was assessed by relative standard deviation (RSD Zn; F2: Zn > Cu; F3: Zn > Cu. Although the concentration of the analytes is above the values allowed by CONAMA 454, according to the RAC the studied species present little mobility (> 10% in the traceable fraction) presenting low risks of biota contamination. Although the concentration of the analytes is above the values compared to those allowed by CONAMA 454, according to the RAC the studied species present low mobility (> 10% in the traceable fraction) presenting low risks of biota contamination. The efficiency of the sequential extraction procedure was evaluated by obtaining extraction percentages in relation to the total concentration of the analytes ranging from (83 to 96%). The conditions for determination of the analytes were evaluated by calculating the characteristic concentrations. The average values found were 0.05 mg L-1 for Cu, 0.07 mg L-1 for Ni and 0.020 mg L-1 for Zn in the extraction media. Detection limit values ranged from 0.3 to 85 mg kg-1 , and quantitation limit values ranged from 0.5 to 26.8 mg kg-1 for Cu, Cr, Ni and Zn respectively.