الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
A fast and simple preconcentration procedure was developed for the preconcentration of inorganic materials (heavy metal ions) from aqueous and environmental samples. Functionalized sorbents, such as polyurethane foams, are very promising materials for the application in on-line and off-line preconcentration systems.
In the present work untreated-PUF was modified by three different techniques and three novel chelating sorbent materials were obtained. The free isocyanate and some urethane groups in PUF could be hydrolyzed by soaking in 5.0 mol L-1 HCl solution for 6.0 hrs to convert the terminal toludine groups to –NH2 which can be diazotized by 1.0 mol L-1 NaNO2 solution. The sorbent materials formed through the coupling of the diazotized foam to the active methylene group of acetoacetanilide (AAA) or ethyl cyanoacetate (ECA) or to the amino group of 2-amino thiazole (2-AT) in the presence of ethyl alcohol and sodium acetate at temperature < 3 ºC.
These novel polymeric phases are proposed as new chelating extractors for solid-phase extraction. It was demonstrated that these new foams present remarkable stability and excellent resistance in particular to organic solvents like ethanol, methanol, isopropyl alcohol, diethyl ether, and acetone and inorganic solvents like 1.0 - 6.0 mol L–1 H2SO4, 1.0 - 6.0 mol L–1 HCl, 2.0 - 4.0 mol L-1 NaOH,
Shaking time, pH, preconcentration, sorption capacity and other parameters for extraction of Ni(II), Zn(II), and Cd(II) onto these materials were studied.
The modified foams in the present study seem to be promising polymeric phases for SPE, which demonstrated to be easily obtained, inexpensive, reliable, stable and more sensitive with a good capacity for the enrichment of some toxic metal ions from aqueous matrices.
The other main advantages of these methods include sensitivity, simplicity, flexibility, time saving, cost-effectiveness and no requirement of sophisticated instruments.
Moreover, the selectivity of the new modified foams due to the high selectivity of the used reagents in the modification processes and the simplicity of FAAS, allows the Ni(II), Zn(II) and Cd(II) determination in the presence of significant amounts of foreign ions generally present in real water samples.
The novel sorbents exhibit a good preconcentration factor for the enrichment of trace of the studied ions from large sample volumes.
The precision obtained in the analysis of real samples show the reliability and accuracy of these new methods.
These characteristics are very important in laboratories for routine analysis equipped only for metal ions determination by FAAS.
The proposed separation-enrichment method is applied for FAAS determination Ni(II), Zn(II) and Cd(II) ions in liquid samples such as Tap water and Qaroun Lake water and solid samples such as Spinach, Parsley and Black Tea leaves at Fayoum City. The obtained results with RSD % < 9% confirmed the reliability of the proposed methods and their application to various natural samples.
The great advantage of these modified foams is that they can extract metal ions without prior complexation as free metal ions other than untreated foam.
The synthesized foam columns were recycled several times without significantly affecting their extraction capacities.
The application of this open cell foam as a packing material for mini- column is recommended.
The moderately HCl concentration required for desorption of the analyte ions avoid any further dilution step for the FAAS measurements which elongates the life-time of the mini-column without affecting its extraction capacity.
No sever sources of interference for the techniques are observed from various tested real samples. The high tolerance to interference allowed to presented advantages is interesting for routine laboratories in trace analysis.
Finally, Functionalized sorbents such as polyurethane foams, are very promising materials for the application in the off-line pre-concentration systems. Some studies on this direction are a focus of future work in this laboratory.