Preconcentration and speciation of thallium by ferrofluid based dispersive solid phase extraction and flame atomic absorption spectrometry

A dispersive solid phase extraction method based on ferrofluid has been proposed for the separation and preconcentration of thallium (I) before its determination by flame atomic absorption spectrometry. The ferrofluid was rapidly injected into the aqueous sample containing the thallium (I) and dibenzo-18-crown-6 (DB18C6) as the chelating agent with a syringe. The separation of the sorbent from the aqueous phase was achieved by the application of an external magnet. The main factors affecting the extraction of thallium (I) were investigated and optimized. Total thallium was determined after the reduction of Tl(III) to Tl(I) by hydroxylamine hydrochloride. Under the optimized conditions with a sample volume of 150.0 mL, the detection limit (based on 3Sb/m) and the enhancement factor were found to be 0.85 μg L- 1 and 298, respectively. The relative standard deviation at 50 μg L- 1 concentration level of Tl(I) was 3.2%. The method was successfully applied to the determination of thallium species in water and waste water samples as well as total thallium in nail, hair, cabbage and iron ore samples. The validity of the method was checked through the recovery experiments besides the analysis of a certified reference material.