Determination of total thallium in water and spinach samples by ligandless microextraction using ion pair-based dispersive liquid–liquid microextraction followed by electrothermal atomic absorption spectrometry

ABSTRACT

An efficient, simple, and sensitive ligandless, ion pair-based dispersive liquid–liquid microextraction technique was used for preconcentration and determination of trace levels of total thallium followed by electrothermal atomic absorption spectrometry. In this method, thallium(ІІІ) was complexed by bromide ion to produce negative charged thallium bromide complex followed by addition of cetylpyridinium chloride as a counterion to form hydrophobic complex which was extracted into the extraction solvent by DLLME. In this method, a mixture of 1.5 mL of methanol (as disperser solvent) containing 150 µL of chloroform (as extraction solvent) was injected as extractant.

Under the optimum conditions, the calibration curve was linear in the range of 0.1–2 µg L⁻¹ of thallium(ІІІ) with a correlation coefficient of 0.9983. The limit of detection was 0.03 µg L⁻¹ and the relative standard deviation based on six replicate analysis of 1 µg L⁻¹ thallium(ІІІ) was 4.1%. The accuracy of the method was checked by the analysis of certified reference material and spike methods. The method was applied for determination of trace levels of thallium in water and spinach samples.

KEYWORDS:

• Cetylpyridinium chloride
• electrothermal atomic absorption spectrometry
• ion pair-based dispersive liquid–liquid microextraction
• ligandless
• thallium