Determination Of Cu(Ⅱ)、Pb(Ⅱ) And Cd(Ⅱ) In Environment Samples By Flame Atomic Absorption Spectrometry After Preconcentration With Modified Silica

The use of solid phase extraction techniques has become popular for extraction separation and enrichment of trace heavy metal ions in environmental samples in recent years. Because it is compared with traditional pretreatment, such as solvent extraction and precipitation separation technology with saving solvent, simple operation, easy automation, etc. The core of SPE is solid phase extractor. So far, numerous materials have been used assolid-phase extractants, such as XAD resins, ion-exchangeresins,cellulosicderivatives,silicagel,polyurethane foam, activatedcarbon and chelating fibers.This article choose silica as solid phase for its good mechanical and thermal stability and its less susceptibility to swelling, etc. It has a strong adsorption, but not selective. In order to realize the highly selective separation and enrichment, the silica gel surface are usually loaded some organic matter containing functional group. In this report, silica gel modified by alizarin complexone dihydrate and dithio oxamide as a solid-phase absorbent was synthesized.The major research contents are summarized as follows:(1) silica gel modified by alizarin complexone dihydrate as a solid-phase absorbent was synthesized, and its adsorption properties were investigated by flame atomic absorption spectrometry. Its characteristics was also investigated by diffuse reflectance UV-Vis spectroscopy and elemental analysis. Conditions for the effective extraction of Cu(II) and Cd(II) were studied. Under the optimized conditions, linear calibration graphs of Cu(II) and Cd(II) were linear in range of 1.0~200 μg·L-1 and 2.5~100 μg·L-1, and detection limits of Cd(II) and Cu(II) were 0.46 μg·L-1 and 0.21μg·L-1, respectively. The total capacity of the sorbent for Cu(II) and Cd(II) were 0.51 mmol·g-1 and 0.16 mmol·g-1, respectively. The relative standard deviations for Cu(II) and Cd(II) were 2.8% and 3.4%, respectively.The recoveries of Cu(II) and Cd(II) spiked in samples were both from 90% to 110%. The proposed method has been applied to determine Cu(II) and Cd(II) in water and rice sample with satisfactory results. By the gradient elution of Cu(II) and Cd(II), Cu(II) could be completely separated from Cd(II) and be monitored with the naked eye using color agent 5-Br-PADAP.(2) a silica gel modified by dithio oxamide as a solid-phase absorbent was synthesized, and its adsorption properties were investigated by flame atomic absorption spectrometry.Its characteristics was also investigated by diffuse reflectance UV-Vis spectroscopy. Conditions for the effective extraction of Cu(II) and Pb(II) were studied. Under the optimized conditions, linear calibration graphs of Cu(II) and Pb(II) were linear in range of 1.0~100 μg·L-1 and 10~300 μg·L-1, and detection limits of Cu(II) and Pb(II) were 0.42 μg·L-1 and 1.0μg·L-1, respectively. The relative standard deviations for of Cu(II) and Pb(II) were 2.3% and 1.8%, respectively. The total capacity of the sorbent for Cu(II) and Pb(II) were19.50 mg/g and 29.39 mg/g, respectively. The recoveries of Cu(II) and Pb(II) spiked in samples were both from 95% to 105%. The proposed method has been applied to determine Cu(II) and Pb(II) in water sample with satisfactory results.