Evaluation of thallium rate in soil after dispersive liquid-liquid micro-extraction

Abstract

Thallium is widely found in nature, but the only inorganic stones full of this element are crookesite and lorandit. It is<br />also found in pyrites of copper, lead and inorganic stones. The element and its compositions are toxic and harmful to the<br />environment; therefore, its application requires caution and further research. It is important to develop sensitive and<br />accurate analytical methods to determine trace levels of thallium in environmental and real samples. In this research,<br />dispersive liquid-liquid microextraction based on solidification of floating organic drop as a sample preparation method<br />was used for separation and preconcentration of ultra-trace amounts of thallium in soil samples prior to graphite-furnace<br />atomic-absorption spectrometry. Investigated effective parameters on extraction include pH, the amount of chelating<br />agent, type and volume of extraction solvent and extraction time. Under optimum conditions, the calibration curve was<br />linear in the range of 0.2-10.0 ng mL−1 of thallium in the original solution, with limit of detection of 0.03 ng mL−1. The<br />relative standard deviation (RSD) for ten replicated determinations of thallium ion at 5.0 ng mL−1 concentration level was<br />calculated as 3.3%. The proposed method was successfully applied to the determination of thallium in soil samples.