Dispersive solid phase extraction of noble metal nanoparticles from environmental samples on a thiol-functionalized Zirconium(IV) metal organic framework and determination with atomic absorption spectrometry

This work reports for the first time, the utility of a thiol-functionalized Zr-metal organic framework (MOF-SH) for the extraction of noble metal nanoparticles from environmental water samples. Due to the presence of a free thiol terminal group, extraction of metal nanoparticles is performed on the external surface area of the MOF, instead of its pores, thus significantly decreasing the extraction time. Both gold nanoparticles and gold ions, as model species, could be quantitatively extracted from aqueous samples using dispersive solid phase extraction and determined with atomic absorption spectrometry. The MOF-SH material could effectively retain AuNPs of variable sizes and coatings thus enabling the determination of the total concentration of AuNPs in the sample. Due to the strong affinity of gold species for the thiol group, the separation of AuNPs from gold ions could be achieved prior to extraction with ultracentrifugation, followed by the independent extraction and determination of each species. Under the optimum experimental conditions, the method could effectively extract and discriminate gold nanoparticles and gold ions from freshwater samples with detection limits for AuNPs as low as 650 femto-mol/L (by extracting 25 mL of water sample), recoveries between 73 and 132% and precision between 11.8 and -13.4%, which are comparable to other methods.