Study On Determination Of Cadmium And Lead By Ionic Liquid Extraction Spectrophotometry

Ionic liquids （ILs） are organic salts and are in liquid form at room temperature.So ILs are aslo called room temperature ionic liquid. ILs are usually composed oflarge organic cations and small inorganic anions. The various ILs can be synthetizedby the adjustment of cations and anions. Compared with conventional organicsolvents, ILs have particular physical and chemical properties, such as negligiblevapour pressure, low melting point, good thermal stability, high viscosity,designability, strong dissolving ability, noninflammability and wide electrochemicalwindow. Because ILs are non-volatility and environmental friendly, ILs have beenconsidered as “green solvents”. In this thesis, two methods were developed based onthe IL （1-butyl-3-methylimidazolium hexafluorophosphate,[Bmim][PF₆]）extraction. Cadion （1-（4-nitrophenyl）-3-（4-pehnylazophenyl） triazene） was used ascomplexing agent, and a new extraction spectrophotometic method to determinetrace cadmium was developed. Dithizone （Diphenylthiocarbazone） was used ascomplexing agent, and a new extraction and back extraction graphite furnace atomicabsorption spectrometry for the determination of lead was developed. The twomethods were applied for the determination of cadmium in environmental watersamples and lead in liquor samples.The IL extraction coupled with spectrophotometey for the determination ofcadmium was developed. The conditions including type of IL, acidity of samplesolution, the amount of Cadion and IL, extraction time and temperature,centrifugation time and speed were optimized. As the results indicated in theexperiment, when the pH=10.8NaB4O7-NaOH buffer solution was used, the amountof [Bmim][PF₆] and Cadion were220μL and100μL respectively, extraction timewas6min at the temperature20℃, the centrifugation time was3min and the speedwas6000r/min, the the maximum absorbance of Cd-Cadion-[Bmim][PF₆] wasmeasured at517nm with the UV-Vis spectrometer. The calibration curve wasconstructed and the linear concentration range was1.0～62.5ng/mL. The limit ofdetection （LOD） was0.22ng/mL and the recoveries of cadmium in three watersamples were from96.7%to108.5%. The present method was compared with the conventional extraction, the extraction was only need one step of manipulation andreduced the using of organic solvents. The method had high extractability andsensitivity, the extraction ratio of50ng/mL was99.6%and the apparent molarabsorption coefficient was6.9×10⁵L·mol^-1·cm^-1. The method was rapid and simple,and also could be applied for the determination on the spot.Pb-Dithizone-[Bmim][PF₆]-HNO₃extraction and back extraction graphitefurnace atomic absorption spectrometry （GFAAS） for the determination of lead wasproposed. The conditions including acidity, the amount of Dithizone and IL, backextraction time and temperature, and centrifugation speed were optimized. When thepH=9.0NH3-NH4Cl buffer solution was used, the amount of [Bmim][PF₆] was200μL, Dithizone was50μL, the concentration of HNO₃was1.0mol/L, extraction timewas10min at the temperature40℃, the centrifugation time is6min and the speed at6000r/min, the absorbance of lead was measured with GFAAS. Compared withaqueous phase, the enhancement factor of this method was26.2, The calibrationcurve was constructed and the linear concentration range was0.08～2.4ng/mL forLead. The LOD was0.03ng/mL and the recoveries of lead in three liquor sampleswere from93.8%to117.5%. The enhance factor was26.2and the detection limit wasvery low. The present method can be applied to the determination of trace lead offood and drinking water.