Thiolated-ionic Liquid For Preconcentraion Of Cadmium Prior To Atomic Absorption Spectrometry Determination

Room temperature ionic liquids were ionic molten salts that were liquids at normal temperature. In this dissertation, we systemically described the structures, characteristics, synthesis and application of the ionic liquids. A new hydrophobic thiol-functionalized ionic liquid (thiol-FIL, TFIL) was employed to extract Cd(II) from water and foods samples prior to analysis by flame atomic absorption spectrometry.The solubility of new synthesized ionic liquid was studied. Thiol-FIL was found to be soluble in acetonitrile and ethanol, dissolved in ethyl acetate by ultrasonic, but was not soluble in weak polar solvents. The purification effects of thin-layer chromatography, recrystallization and simple washing for thiol-FIL were investigated, of which-20℃recrystallization in acetonitrile was the best. Then, the thiol-FIL was characterized by ESI-MS, FT-IR and1H NMR。Factors that influence the extraction of Cd and the nature of stripping solutions were optimized and studied. The results showed that, in weakly acidic condition, Cd(II) was extracted into ionic liquid phase. The initially feed aqueous solution was50mL with hydrochloric acid/ammonium acetate as buffer medium while the ionic phase was the mixture of [C4mim][PF6] and thiol-FIL. The amount of FIL was0.076g mL-1. The stripping solution and conditons were as follows:2mL1%H2O2in1.2mol L-1HC1with shaking time of5min. The linear range of the determination was1.5-60μg L-1in aqueous solution. The detection limit (3SD) was found to be0.39μg L-1. The relative standard deviation of11replicate extractions of10ng cadmium(II) in50mL soluton was1.57%.The tolerance limit of coexistent ions was also investigated. The presence of10mg L-1(1000-fold) species Na(I), Mg(II), Ca(II), Pb(II), Hg(II), Mn(II), Fe(III), Al(III), Cu(II), Zn(II), Ni(II), Cr(III), Co(II), Ag(I) and As(III), had no significant effect on the extraction and determination of10μg L-1Cd(II), while APDC or DDTC appeared to be seriously interfered even when the concentration of certain co-existing ions was very low. The recovery of0.2mg L-1(20-fold) Cu(II),0.8mg L-1(80-fold) Hg(II) for the determination of10μg L-1Cd(II) using DDTC or APDC as extractants were found to be78.5%and91.8%, respectively.The recoveries of cadmium spiked river water and food samples ranged from97to102%. The proposed method was validated by determination of cadmium in certified reference materials and was shown to be promising for the detennination of cadmium in real water and food samples.