Preconcentration of thallium (III) by single drop micro extraction and its determination by electrothermal atomic absorption spectrometry in real samples and speciation of thallium (I) and (III)

Abstract

Abstract<br><br>Single drop micro extraction (SDME) in combination with electrothermal atomic absorption<br><br>spectrometry has been used to preconcentrate and determine thallium (III) ions followed by<br><br>speciation of thallium (I) and (III). 10.0 ml of aqueous sample of thallium containing 0.5 ml of<br><br>1% picric acid as a counter ion at pH= 6 was extracted into a 4 μl microdrop of nitrobenzene<br><br>containing dyciclohexano-18- crown-6 as complexing agent. After the extraction, the<br><br>microdrop was injected into a graphic furnace for thallium determination. Different parameters<br><br>affecting the extraction efficiency such as the type organic solvent, concentration of picric acid<br><br>and crown ether, volumes of organic and aqueous phases, pH, extraction time and temperature<br><br>were optimized. The effects of different interfering ions and methods of their eliminations were<br><br>conducted. Under the optimized conditions, thallium (III) was determined with detection limit<br><br>of 1.1 ng ml-1 and sensitivity of 0.3 ng ml-1. Relative standard deviation for five replicate<br><br>analysis of 10 ng ml-1 of thallium (III) was 4.2 percent. The calibration curve was linear in the<br><br>range of 1.1-32 ng ml-1 of thallium. The enrichment factor was calculated to be 80. Thallium (I)<br><br>and (III) speciation has been performed on the basis that thallium (III) forms a stable complex<br><br>with EDTA and would not enter into the micro drop and hence only thallium (I) can be<br><br>determined. The accuracy and validity of the method was evaluated using real samples of nail<br><br>and spiked tap water and also certified reference material.