Functionalized Fe_3O_4/graphene oxide nanocomposites with hairpin aptamers for the separation and preconcentration of trace Pb~(2+) from biological samples prior to determination by ICP MS

摘要

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 Pb~(2+) in biological samples, based on the guanine (G)-quadruplex formed by the aptamer with hairpin structure and Pb~(2+). For this purpose, Pb~(2+) specific aptamer serving as affinity probe to capture and separate trace amounts of the analyte, was covalently linked to Fe_3O_4/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 Pb~(2+). Inductively coupled plasma mass spectrometry (ICP-MS) was used for determination of Pb~(2+) 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 µg L~(-1) and an enrichment factor (EF) of 50 was obtained. The limit of detection (LOD) was 0.05 µg 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).