Ionic liquid ultrasound assisted dispersive liquid-liquid/micro-volume back extraction procedure for preconcentration and determination of ultra trace amounts of thallium in water and biological samples

A simple, highly sensitive and environment-friendly method, combined with flame atomic absorption spectroscopy (FAAS) is developed to preconcentrate and determine trace amounts of thallium in aqueous solutions. In the preconcentration step, the thallium (I) from 30mL of an aqueous solution was extracted into 350 mu L of ionic liquid, 1-hexyl-3-methylimidazolium hexaFLuorophosphate [Hmim][PF6], containing dicyclohexyl-18-crown-6 (DCH-18-crown-6) as complexing agent. Subsequently, the DCH-18-crown-6 complex was back-extracted into 300 mu L of nitric acid (2molL(-1)) solution, and analyzed by FAAS. Several parameters inFLuencing the extraction and determination of thallium, such as pH, concentration of DCH-18-crown-6, sonication and centrifugation times, sample volume, ionic liquid amounts, ionic strength, and concentration of stripping acid solution, were optimized. Under optimum conditions, the calibration graph was linear in the range of 5 to 400ngmL(-1), the detection limit was 0.64ngmL(-1) (3S(b)/m, n=7), the enhancement factor was 98.2 and the relative standard deviation was +/- 1.43%. The results for preconcentration and determination of trace amount of thallium in waste water, well water, tap water, sea water, human hair and nail demonstrated the accuracy, recovery and applicability of the presented method.