Research On The Determination Of Heavy Metal Ions In Environmental Water Samples

Heavy metals are stable and difficult to degrade. They could cause serious pollution when released into the environment, and some of heavy metal ions may be harmful to the health of human body when eventually enter the body through the food chain. Therefore, monitoring of the level of heavy metals has important significant on the prevention and treatment of ecological environment and human health. Direct determination of heavy metal ions at trace levels is limited due to their low concentrations and matrix interferences. Thus, preconcentration and separation techniques are still very necessary. In this paper, analysis methods of four heavy metal ions including copper (Cu), nickel (Ni), lead (Pb) and cadmium (Cd) have been studied. The main contents are as follows:Part1Ultrasound-assisted cloud point extraction coupled with flame atomic absorption spectrometry for the determination of lead and cadmium in water samplesA new method based on ultrasound-assisted cloud point extraction (UA-CPE) using the mixture of non-ionic surfactant polyoxy ethrlene nonyl phinyl ether (NP-7) and polyoxy ethrlene nonyl phinyl ether (NP-9) for the preconcentration of trace amount of lead (Pb) and cadmium (Cd) in water samples prior to determination by FAAS had been developed. Variable parameters affecting the CPE procedure were evaluated and optimized. The optimum conditions of UA-CPE were pH5.0,10μg/mL APDC,0.5%(v/v) mixed surfactant and25min equilibration time at55℃. The calibration graph was linear in the range of10-500μg/L for Pb and Cd. The detection limits were0.5μg/L and0.28μg/L with the relative standard deviations (RSD, n=6) of2.6%and3.4%for Pb and Cd, respectively. Recoveries of Pb and Cd spiked into water samples were in the range of96.9-100.4%. The enrichment factors are57and63for Pb and Cd, respectively, for10mL of preconcentrated solution.Part2Study on the determination of heavy metals in water samples with ultra sound-ass is ted dispersive liquid-liquid microextraction prior to FAASA ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) method using Triton X-114as disperser solvent and CCl4as extraction solvent was developed for extraction and preconcentration of Cu, Ni, Pb and Cd in water samples. The optimum conditions of UA-DLLME were pH8.0,10μg/mL TAN,500μL Triton X-114(1%) and100μL CCl4. Under the optimal conditions, the calibration curve was linear in the range of10-800μg/L for Cu and Ni,10-500ug/L for Pb, and10-1000μg/L for Cd, respectively. The limits of detection for Cu, Ni, Pb and Cd were0.4μg/L,0.45μg/L,0.5μg/L and0.4μg/L, with the enrichment factors of105,66,28and106, respectively. The relative standard deviations (RSD, n=6) were2.6-4.1%. The proposed method was applied to determination of Cu, Ni, Pb and Cd in water samples and satisfactory relative recoveries (93.0-101.2%) were achieved.Part3Supramolecular solvent-based microextraction of copper and lead in water samples prior to reacting with synthesized Schiff base by flame atomic absorption spectrometry determinationA new Schiff base was synthesized between4-aminoantipyrine and p-dimethylaminobenzaldehyde (DMAB) and used as the chelating agent in this study. A supramolecular solvent made up of reverse micelles of nonanoic acid, dispersed in a continuous phase of tetrahydrofuran (THF) and water, was proposed for the extraction and preconcentration of copper (Cu) and lead (Pb) in water samples prior to flame atomic absorption spectrometry determination The optimum conditions of the proposed method were pH7.0,10μg/mL Schiff base,1mL supramolecular solvent and5min centrifugation time at3500rpm. Under the optimized conditions, the calibration curves were linear in the range of10-800μg/L for Cu and10-500μg/L for Pb, respectively. The limits of detection (LOD) were0.29μg/L and0.45μg/L for Cu and Pb, respectively. The relative standard deviations (RSD, n=6) were2.3-3.6%. Recoveries of Cu and Pb spiked into water samples were in the range of91.2-102.1%.