The microdetermination of thallium by ICP-AES after previous preconcentration on modified silica. Comparison with integrated-platform graphite atomic absorption spectrometry

Abstract.

The extensively used technique of ICP-AES determination of thallium at optimal lines 190.864(1) nm and 190.864(2) nm in different orders n ₁ = 135 and n ₂ = 136 shows just limited sensitivity. Thus, Tl^IIICl₄ ⁻ was preliminarily separated and pre-concentrated on modified silica C18 in the form of ion associate with various cationic surfactants. The surfactant Zephyramine with 0.1 M HCl served as a sorbent surface activator during quantitative sorption of 5–20 µg of thallium(III) from 15–1000 mL of aqueous solutions. The subsequent elution with 96% ethanol and the final determination with ICP were carried out after evaporating the solvent. Limited interference by SO₄ ²⁻, NO₃ ⁻, Cl⁻, Na⁺, K⁺, Ca²⁺, Mg²⁺, Al³⁺ and Fe³⁺ during the sorption was observed. The above procedure is applicable for the determination of thallium in surface and mineral waters.

The use of PdMg(NO₃)₄ or NH₄VO₃ modifiers and Zeeman splitting for the sample background elimination with the integrated-platform graphite AAS technique at 276.8 nm was found to be suitable for the direct determination of thallium(I) up to 30 ng in the presence of the following species: large amounts of chlorine, 100 fold excess of NO₃ ⁻, SO₄ ²⁻, Ca²⁺, Mg²⁺, K⁺, Al³⁺ and Fe³⁺. The temperature program starting by stepwise drying between 90 and 110 °C followed by pyrolysis at 700 °C and the atomisation at 1700 °C was optimized this way. This method can be applied for the determination of thallium in urine and spruce needles.