In situ ultrasound-assisted preparation of Fe3O4@MnO2 core-shell nanoparticles integrated with ion co-precipitation for multielemental analysis by total reflection X-ray fluorescence

Abstract

In this work, a new analytical approach based on in situ ultrasound-assisted preparation of manganese dioxide coated magnetite nanoparticles (Fe3O4@MnO2 NPs) was applied for extraction and preconcentration of Ni, Cu, Zn, Tl, Pb, Bi and Se. The Fe3O4@MnO2 core-shell nanocomposite was synthesized by application of high-intensity sonication to an aqueous reaction medium in the presence of the target analytes, which are trapped during NPs formation. In this way, synthesis of the nanosorbent and extraction can be simultaneously accomplished within only 30s. After the extraction step, the resulting Fe3O4@MnO2 NPs enriched with the target analytes were separated by an external magnetic field, so that filtration or centrifugation steps were unnecessary. A 10μL aliquot of the solid phase was deposited onto a sample carrier (quartz reflector) and directly analyzed by total-reflection X-ray fluorescence (TXRF) without the need for an elution step. A comprehensive characterization of the Fe3O4@MnO2 NPs was carried out by transmission electron microscopy and TXRF. Detection limits ranged from 0.19 to 0.98μgL−1 depending on the analyte. Enrichment factors in the range of 402–540 were obtained. The repeatability expressed as relative standard deviation was around 1.7% (N=5). The accuracy of the proposed method was assessed by analyzing the certified reference material BCR®-610 (groundwater). An effective, simple, rapid and sensitive procedure for multielemental analysis of water samples was accomplished.