Functionalized magnetic composites based on the aptamer serve as novel bio-adsorbent for the separation and preconcentration of trace lead.

A magnetic functionalized bio-sorbent based on aptamer was designed for the selective separation of ultra-trace Pb2+, shortly termed as Fe3O4@Au@DNA. Pb(II) specific aptamer attached to the magnetic solid substrate served as affinity probe to capture and separate trace lead. Oligonucleotides with a polyA block were employed for the immobilization on the surface of AuNPs, with adenine sequences (polyA) as the part of effective anchoring block. The prepared Fe3O4@Au@DNA composites were characterized by FT-IR, SEM and XPS. The binding of lead on Fe3O4@Au@DNA composites surface was pH-dependent, the adsorption follows Langmuir model, and the adsorption dynamic fits the pseudo-second-order kinetics model. Procedure for lead separation and preconcentration was explored and combined with detection of graphite furnace atomic absorption spectrometry (GFAAS). Under the optimum condition, an enrichment factor of 17.73 was obtained with a sample volume of 1.0 mL. The limit of detection (LOD) was 57 ng L-1 along with a relative standard deviation (RSD) of 2.06 (n = 9). The procedure was further validated by a certified reference material GBW08608 and several environmental and blood samples.