Ultra-trace determination of total Thallium using ion pair based dispersive liquid liquid microextraction followed by electrothermal atomic absorption spectrometry

An efficient, simple and sensitive ion pair based dispersive liquid liquid microextraction technique was used for preconcentration and determination of ultra-trace levels of total thallium followed by electrothermal atomic absorption spectrometry (ETAAS). In this method, Tl (ІІІ) was complexed by bromide ion (Br-) to produce TlBr4- followed by addition of cetylpyridinium chloride (CPC) as a counter ion to form hydrophobic complex of TlBr4-CPC. The resulting complex was extracted into the extraction solvent by dispersive liquid liquid microextraction (DLLME). In DLLME, a mixture of 1.5 mL of methanol (as disperser solvent) containing 150 μL of chloroform (as extraction solvent) was rapidly injected into the sample solution to extract the hydrophobic TlBr4-CPC complex. The important parameters affecting the extraction efficiency such as HBr concentration (as a source of bromide anion), CPC concentration and type and volume of the extraction and disperser solvent were investigated and optimized in details. Under the optimum conditions, the calibration curve was linear in the range of 0.1 – 2 μg L-1 of Tl (ІІІ) with a correlation coefficient of 0.9992. The limit of detection (LOD) was 0.03 μg L-1 and the relative standard deviation (RSD, %) based on six replicate analysis of 1 μg L-1 Tl (ІІІ) was 4.1 %. The accuracy of the method was checked by the analysis of certified reference material (CRM) and spike methods. The proposed method was successfully applied for determination of ultra-trace levels of Tl in different water samples

Keywords:

Thallium , Bromide ion , Ion paired based dispersive liquid liquid microextraction , Electrothermal atomic absorption spectrometry