The authors describe a magnetic metal-organic framework nanocomposite consisting of aminodibenzo-18-crown-6 magnetite nanoparticles and MIL-101(Cr). It was employed to the speciation analysis of Tl(I) and Tl(III) ions. The sorbent is capable of selectively extracting Tl(I) while Tl(III) remains in solution. The total amount of thallium was then determined by reducing Tl(III) to Tl(I) by hydroxylamine hydrochloride and also extracting it. The extraction parameters were optimized by employing design of experiments methodology. Thallium was quantified by ET-AAS. Under optimized conditions, the detection limit is as low as 1.5 ng L-1, the quantification limit is 5.0 ng L-1, the linear range extends from 5 to 400 ng L-1, and the relative standard deviation is <12% (for n = 5 at levels of 5, 50 and 250 ng L-1). The recoveries of real samples analysis were in the range of 90-106%. The method was successfully applied to the analysis of a certified reference material (NIST SRM 1643d water sample) and to various real water samples. Graphical abstract A novel metal-organic framework nanocomposite consisting of aminodibenzo-18-crwon-6 magnetite nanoparticles (Fe3O4@ADB18C6) and MIL-101(Cr) was synthesized, characterized and employed to speciation analysis of Tl(I) and Tl(III).
Keywords: Design of experiments; Electrothermal atomic absorption spectrometry; Magnetic separation; Metal-organic framework; Selective extraction; Speciation; Thallium.