Preconcentration and Solid Phase Extraction of Trace Metal Ions by Chemically Modified Graphene Oxide Nanoconstructs

The toxicity of arsenic and mercury is highly dependent on their unique chemical forms, mobility, bioavailability, and biological roles. This places a strong demand on specific metal species analysis rather than total quantification. Graphene oxide (GO) is an excellent adsorbent for the extraction of metal ions; however, the functional moieties on the GO surface are not metal ion-specific. In this work, we chemically introduced thioglycolic acid to improve metal ion selectivity after the dual oxidation of graphite to generate graphene oxide (GO) nanosheets. The prepared adsorbent was characterized by various spectroscopic and microscopic techniques. A solid phase extraction method was developed after careful analysis and optimization of the prepared sorbent. The method shows a fairly good quantification limit of 0.20 µg L⁻¹ for As(III) and Hg(II) ions. From diverse water samples, the proposed sorbent preferentially removes As(III) and Hg(II) ions (tap water and groundwater). The remarkable wettability and analyte accessibility that the surface-bonded thiol functionality of GO sheets offers is an exciting feature. In a lesser amount of time, the GO−SH nanosorbent exhibits good extraction of traces of As(III) and Hg(II). The developed method exhibits good reliability and precision in terms of accuracy and relative standard deviation (RSD 3.8%; N = 5) and has low detection limits (0.04 µg L⁻¹). Real samples that had been spiked to a predefined level were analyzed in order to validate the established procedure.