Síntese e caracterização de nanotubos de carbono de acesso restrito magnético e seu uso para extração de chumbo e cádmio em amostras de leite

Abstract

In this work, magnetic restricted access carbon nanotubes (M-RACNTs) were used to extract lead and cadmium from untreated milk sample. These materials were obtained by modifying commercial carbon nanotubes (CNTs) with magnetite nanoparticles and subsequent surface functionalization with a chemically modified layer of cross-linked bovine serum albumin (BSA). The M-RACNTs were employed as sorbents for the extraction and pre-concentration of Pb2+ and Cd

2+ directly from milk samples, using magnetic dispersive solid phase extraction. Thus, the mineralization step of the biological sample was not need. Because they are magnetic materials, the M-RACNTs could be separated from the sample with a neodymium magnet, and the metals were determined by flame atomic absorption spectrometry. The extraction parameters were evaluated by multivariate optimization (factorial design and Doehlert matrix). The validated method proved to be simple, fast, sensitive, selective, robust and precision. In addition, coefficients of determination ≥ 0.99 and the limit of quantification of 10 μg L-1 were obtained for Pb2+ and Cd2+ ions. The developed method was able to determine both metals in concentrations below the maximum residue limits established by the National Health Surveillance Agency for milk (20 and 50 μg L-1

for Pb2+ and Cd2+, respectively), demonstrating that M-RACNTs are promising materials for extraction of metals from complex samples, without the need for mineralization procedures.