Determination of lead and cadmium in non-mineralized raw milk samples employing extraction with magnetic restricted access carbon nanotubes followed by FAAS analysis

Abstract

Abstract Lead and cadmium were determined in non-mineralized raw milk samples employing dispersive solid phase extraction with magnetic restricted access carbon nanotubes (M-RACNTs), followed by flame atomic absorption spectrometry analysis. M-RACNTs were obtained by modifying carbon nanotubes (CNTs) with magnetite nanoparticles and then covering with a chemically crosslinked bovine serum albumin (BSA) external layer. The M-RACNTs particles were very efficient to capture the metals and exclude proteins from the milk, being easily separated from the sample using a neodymium magnet. The extraction parameters were appraised by multivariate optimization (factorial design and Doehlert matrix). The method was validated and proved to be robust for small variations, simple, fast, sensitive and selective. The determination coefficient and limit of quantification were 0.998 and 10 µg L-1, respectively, for both Pb2+ and Cd2+ ions. The developed method was able to determine both metals in concentrations below the maximum residue limits (20 and 50 µg L-1 for Pb2+ and Cd+, respectively, in Brazil), demonstrating that M-RACNTs are promising materials for metal extraction in protein-rich samples, without the need for mineralization procedures.