Improvement in thallium hydride generation using iodide and Rhodamine B

•It was confirmed that the chemical generation of TlH with THB needs to use enhancement reagent.•HNO3 resulted the most appropriated acid for TlH generation.•Addition of Rhodamine B+KI represented a 7.5-fold improvement in sensitivity.•HCl resulted unsuitable for thallium hydride generation.

A continuous flow hydride generation atomic absorption spectrometry (CF-HG-AAS) system was used to study the enhancement effect of different substances for conventional chemical HG of thallium. At room temperature, the acidified sample solution containing the respective enhancement reagent merged with the aqueous NaBH4 solution. The generated thallium hydride was stripped from the eluent solution by the addition of a nitrogen flow and thereafter the bulk phases were separated in a gas–liquid separator. The main factors under study were concentration and type of enhancement reagent (Te, iodide added as KI, Rhodamine B, malachite green and crystal violet) and acid (HCl, H2SO4 or HNO3). Other parameters affecting the thallium hydride generation, such as: NaBH4 concentration, carrier gas flow rate, length of reaction-mixing coil and reagents flow rates, were studied and optimized. Among the enhancement reagents tested, the combination of Rhodamine B and iodide produced the best results. A linear response was obtained between the detection limit (LOD (3σ)) of 1.5 μg L−1 and 1000 μg L−1. The RSD% (n=10) for a solution containing 15 μg L−1 of Tl was 2.9%. The recoveries of thallium in environmental water samples by spiking the samples with 10 and 20 µg L−1 of Tl were in the 97.0–102.5% range. The accuracy for Tl determination was further confirmed by the analysis of a water standard reference material (1643e form NIST, USA). Finally, it was demonstrated that malachite green and crystal violet showed similar enhancement effect like Rhodamine B for thallium HG.

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