Síntese e aplicação de nanotubos de carbono de acesso restrito para extração/pré-concentração de cádmio diretamente de amostras de soro humano seguido de análise por espectrometria de absorção atômica

Abstract

In this paper, we proposed a new sorbent able to extract metal ions directly from untreated biological fluids, excluding simultaneously all the proteins from these samples. The sorbent was obtained through the modification of carbon nanotubes (CNTs) with an external bovine serum albumin (BSA) layer, resulting in a restricted access carbon nanotube (RACNT). The BSA layer was fixed though the interconnection between the amines groups of the BSA by using glutaraldehyde as cross-linked reagent. When a protein sample pass through a cartridge containing RACNTs, if the sample pH is larger than the isoelectrical point of the proteins, both proteins from the sample and from the BSA layer are negatively ionized and its causes electrostatics repulsion between them. At the same time, the metal ions are adsorbed in the CNTs after their passage through the chains of proteins. The Cd²+ ion was selected for a proof-of-principle case to test the suitability of the RACNTs due to its toxicological relevance. RACNT was able to extract Cd2+ and to exclude about 100% of the proteins from the human serum samples. The limits of detection and quantification were 0.24 and 0.80 μg L− ¹, respectively. The sampling frequency was 8.6 determinations/h, and the intra and inter-day precisions at the 0.80, 15.0 and 30.0 μg L-¹ Cd2+ levels were lower than 10.1% (RSD). The recoveries of spiked analytes in the human blood serum samples studied ranged from 93.4 to 110.9%. The method was successfully applied to analyze Cd2+ directly from human blood serum samples without any pretreatment.