Functionalized Fe3O4/graphene oxide nanocomposites with hairpin aptamers for the separation and preconcentration of trace Pb2+ from biological samples prior to determination by ICP MS

Lead (Pb) as a topically poisonous metal represents a serious threat to the ecological environment and especially to human beings. Therefore, it is urgent to develop a rapid and reliable monitoring technique for this heavy metal in the environmental samples. In the present study, we have designed a selective and sensitive method for the determination of ultratrace contents of Pb2+ in biological samples, based on the guanine (G)-quadruplex formed by the aptamer with hairpin structure and Pb2+. For this purpose, Pb2+ specific aptamer serving as affinity probe to capture and separate trace amounts of the analyte, was covalently linked to Fe3O4/graphene oxide (GO) surface by using a suitable cross-linking agent. Then, the G-quadruplex complex was formed by the opening of the "neck-ring" of the hairpin structure of aptamer in the presence of Pb2+. Inductively coupled plasma mass spectrometry (ICP-MS) was used for determination of Pb2+ in biological matrices. The analysis conditions were optimized and the performance of the proposed method was investigated. Under optimum conditions, the calibration curve was linear over the range of 03-867.5 mu g L-1 and an enrichment factor (EF) of 50 was obtained. The limit of detection (LOD) was 0.05 mu g L-1 and the relative standard deviation (RSD) for single-sorbent repeatability and sorbent-to-sorbent reproducibility were <4.7% and 8.8% (n = 5), respectively. The accuracy of aptamer-based affinity purification method was confirmed by the analysis of quality control materials (QCMs, Seronorm (TM) Blood REF NO 201505 and Urine REF NO 2525). (C) 2017 Elsevier B.V. All rights reserved.