| Dispersive liquid liquid microextraction(DLLME),which is a new mode of liquid phase microextraction,have many virtues such as solvent-free,rapidly and higher enrichment factor.Among the extraction solvents studied presently,room temperature ionic liquid which can be considered as environmentally benign solvent,has shown great potential in microextraction techniques studied,for its unique physicochemical properties including negligible vapour pressure,good thermal stability,tunable viscosity and miscibility with water and organic solvent.However,the determining total concentration of element can't provide the required information about mobility,bioavailability,and finally the impact of element on ecological system or biological organism.Element speciation analysis identifying and measuring species becomes a focus in analytical chemistry.So far,without the extractant,there're many reports about the metals distribution between ionic liquid and aqueous,but handle studied of element species partition in ionic liquid.Meanwhile,few reports was pubilished which investigated RTILs based DLLME technology applied for speciation analysis.Therefore,it's necessary to investigate the RTILs based DLLME technology application for metals and speciation analysis.The dissertation have studied the distribution of element speciation between ionic liquid and aqueous solution,and developed a new method of room temperature ionic liquid based dispersive liquid-liquid microextraction(RTIL-based DLLME).The conditions were optimized and applied to determine the trace element speciation in water samples.The main studies are summarized as follows:(1) The distributions of Cr(Ⅲ) and Cr(Ⅵ) between ionic liquid and aqueous solution were investigated,because there was difference among metals.Then a new method of ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction(IL-based USA-DLLME) prior to graphite furnace atomic absorption spectrometry(GFAAS) was developed for the determination of Cr(Ⅵ) in water samples.The IL-based USA-DLLME procedure is characterized with no need of volatile solvent and organic dispersive solvent comparing with traditional DLLME.Cr(Ⅵ) was transformed into hydrophobic chelate by reaction with ammonium pyrrolidinedithiocarbamate(APDC),and the chelate was extracted into the fine droplets of 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6]),which dispersed as cloud in the bulk aqueous sample with the help of an ultrasonic probe.Several variables affecting the formation and extraction of chromic chelate such as pH,concentration of APDC,initial volume of[Hmim][PF6]and cooling time were investigated and optimized.Under the optimum conditions,the detection limit of Cr(Ⅵ) as low as 0.07μg L-1 was obtained,while the relative standard deviation for five replication determination of 2.0μg L-1 was 9.2%.The proposed method was applied to the determination of Cr(Ⅵ) in several water samples and the recoveries of spiked samples were in the range of 96-101%.(2) A new method for extraction and preconcentration of Fe(Ⅱ) and Fe(Ⅲ) in water samples using temperature controlled[C8mim][PF6]-based dispersive liquid-liquid microextraction(TC-[C8mim][PF6]-based-DLLME) and UV-Vis spectrophotometry was established.Optimization of variables such as pH,1,10-phenanthroline concentration, volume of ionic liquid,water bath temperature and time,cooling time,and ascorbic acid concentration were studied.The results showed that,250μL[C8mim][PF6]was added to 50 mL pH=7.0 aqueous solution containing 100μg L-1 Fe(Ⅱ) and 0.03%(m/v) 1, 10-phenanthroline.The mixture was immersed into 70℃water bath for 6 min,and then cooled in ice bath for 10 min forming cloudy solution,separated and determined by UV-Vis spectrophotometry.Total Fe was determinated after the reduction of Fe(Ⅲ) by 0.1 %(m/v) ascorbic acid and Fe(Ⅲ) was calculated by difference.The detection limit was 0.93μg L-1,with an enrichment factor of 50.The proposed method was successfully applied to the determination of trace Fe(Ⅱ) and Fe(Ⅲ) in real water samples and offered the advantages of simplicity,repidity and environment friendliness.(3) The partition of metals in ionic liquid was varied without extractant,so the distribution of mercury species was studied.And a new method of speciation of mercury by temperature controlled[C6mim][PF6]-based dispersive liquid-liquid microextraction (TC-[C6mim][PF6]-based-DLLME) combined with HPLC was studied.Variables affecting the formation and extraction of mercury dithizonates were optimized.80μL [C6mim][PF6]was added to 10 mL pH=1.5 aqueous solution containing 10μg L-1 MeHg, PhHg and Hg(Ⅱ)(as Hg) and 0.005%(m/v) dithizone.The mixture was immersed into 70℃water bath for 12 min,and then cooled in ice bath for 10 min forming cloudy solution,separated and determined by HPLC.THF:MeOH:(0.1 M HAc/AcNa pH 4.0 containing 50μM EDTA)(40:30:30) at 0.8 mL min-1 flow rate was selected as mobile phase.MeHg,PhHg and Hg(Ⅱ) were separated in 14 min,with enrichment factor of 244, 318 and 194 respectively.This method presents a lower detection limit,higher preconcentration factor and sensitivity.
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