Abstract
Alumina (Al2O3) with an average particle size of 63 μm was modified with the anionic surfactant sodium dodecyl sulfate (SDS) and then applied to (i) solid phase extraction and separation of both thallium(I) and thallium(III), and (ii) preconcentration of Tl(III) from waste water samples. Only Tl(III), in the form of its complex with diethylenetriaminepentaacetate (DTPA), was retained on the sorbent, from where it can be eluted with 40 % nitric acid. Thallium species were then quantified by ICP MS. The method was characterized by a LOD of 25 pg of Tl(I) and 160 pg of Tl(III) in 10 mL samples. A large excesses of Tl(I) over Tl(III) was tolerated, and relatively high levels of other metal ions, such as a 500-fold excess of Pb(II) and Cd(II), and a 2000-fold excess of Zn(II), respectively, do not interfere. The sorbent was easily prepared and possesses a high loading capacity, and these properties make it an attractive material for rapid and efficient extraction and speciation of Tl.Graphical abstract:Schematic of the SPE procedure for separation (with preconcentration) of Tl(III) from Tl(I) was developed and applied to direct speciation analysis of thallium in wastewater. Self-made columns packed with alumina coated with SDS were used. The method is resistant to interferences from Pb, Cd, Zn and tolerates a large excess of Tl(I) over Tl(III).
Highlights
Thallium occurs in the environment at a low level of concentration; it is toxic even in trace amounts
Chromatographic separation hyphenated with elemental detection is the most common method applied in speciation analysis
We developed a new method of direct speciation analysis of thallium, based on solid phase extraction using Al2O3-sodium dodecyl sulfate (SDS) as a sorbent
Summary
Thallium occurs in the environment at a low level of concentration; it is toxic even in trace amounts. The dominant species of Tl is a free cation of Tl(I), and noticeable amounts of Tl(III) were found in water (21–26 ng L−1) [1], Chromatographic separation hyphenated with elemental detection is the most common method applied in speciation analysis. After conservation of the sample Tl(I) exists as a cation and Tl(III) as a large anion ([Tl(III)DTPA]2− or Tl(III)Cl4−). In the separation process cation exchange, anion exchange, and size exclusion mechanisms can be applied [8, 10, 13]. The separation can be carried out in the normal and reversed phase mode [10, 14]. The ratio between the content of Tl(I) and Tl(III) is a very important parameter determining the choice of chromatographic column
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