Study On Determination Of Mercury, Copper And Iron By Lonic Liquid Extraction Coupled With Spectrophotometric Detection

ILs are composed of unsymmetrically substituted nitrogencontaining cations with inorganic anions.They are liquid at room temperature and pressure.They have negligible vapour pressure,high viscosity,good electrical conductivity,good thermal stability, designability and strong extracting power. Due to such unique chemical and physical properties, room temperature ionic liquids are called green solvents. Room temperature ionic liquids have been widely used in analytical chemistry in recent years. There not much papers about ionic liquids extraction of metal ions.In this paper,dithizone,sodium diethyldithiocarbamate(DDTC) and 1,10-phenanthroline monohydrate(phen) were employed as metal chelators to form Hg(II)-dithizone complex,Cu(II)-DDTC complex and Fe(II)-phen complex,respectively. Room temperature ionic liquids [Bmim][PF6] was employed as extraction agent.The proposed procedure of extraction was developed and applied for mercury,copper and iron determinations in tap water,underground water and polluted water. The result was satisfactory.Hg(II)-H2Dz-[Bmim][PF6],Cu(II)-DDTC-[Bmim][PF6] and Fe(II)-phen-[Bmim][PF6] coupled with spectrophotometry based on room temperature ionic liquids (ILs) was developed for preconcentration and determination of trace mercury,copper and iron using micro cuvette and UV-vis spectrometer. The best conditions including type and amount of ionic liquids, amount of complexing agents, temperature and the other parameters were optimized. The results indicated that the best acidity of detecting mercury, copper and iron was 0.5 mol·dm-3, pH=8 and pH=5-6. The volume of ionic liquid was 200-300μL. The volume of complexing agents was 30-500μL. Extraction time was 10min.Centrifugation rate and centrifugation time were 3000rpm and 4min, respectively. The optimum temperature was room temperature. The stable time were at least 2 hours.The enhancement factor were 47,42 and 55, respectively; The molar absorptivity(e) were 4.3x106,5.7x105 and 0.9x106 L-mol-1·cm-1, respectively; The limit of detections(LOD) were 0.3.0.2.1.0 ng-mL-1; The linear ranges for the determination of mercury, copper and iron were 0.99-112,0.66-71,3.3-60 ng-mL-1. The procedure could be finished in 30min.The proposed procedure was applied for mercury,copper and iron determinations in tap water,underground water and sewage water. The recovery ratio was between 90.3% and 103.3%,97.1% and 113.4%,93.2% and 104.0%.The RSD (n=5) was between 1.6 and 8.7%,1.4 and 7.1%,0.9 and 4.6%.In this paper,comparing to water phase spectrophotometric detection,the enhancement factors of ionic liquids ectraction were almost 50. Furthermore, the amounts of Ionic liquids was little(300μL,at the most). The volume of sample was little(7mL,at most). As green solvents, the ILs do not pollute the enviorment. The proposed method have the advantages of short reaction time(at most 30min), easy operation, high sensitivity,good selectivity and stability.This method can be applied to the detection of Hg2+,Cu2+ and Fe3+ of enviorment water and food.