Enrichment And Analysis Of Heavy Metal Ions By Graphite Furnace Atomic Absorption Spectrometry

This dissertation is focused on the development of new methods for heavymetals extraction and enrichment and their subsequent quantitative analysis via graphitefurnace atomic absorption spectrometry (GFAAS). Cloud point and solid phaseextraction were utilized as sample pretreatment techniques. Nickel, cadmium and leadwere extracted and preconcentrated using these strategies.A new method based on the cloud point extraction (CPE) for separationand preconcentration of nickel (â…¡) and its determination by GFAAS was designed.8-hydroxyquinoline was used as chelating agent to form a hydrophobic complexwith nickel(â…¡). The micelles of Triton X-100entrapped the resulting hydrophobiccomplex which was extracted into the small volume surfactant rich phase. The phaseseparation was achieved by heating the miceller solution above cloud point temperature(CPT) of the surfactant. This step simultaneously extracted and preconcentrated the traceamounts of nickel(â…¡) present in the sample solution. The factors which affect the cloudpoint extraction and GFAAS analysis i.e. pH, ligand concentration, surfactantconcentration, incubation time, pyrolysis and atomization temperature, centrifugation rateand time were thoroughly investigated and optimized. The effect of different inorganicsalts on the cloud point temperature was also explored. The addition of sodium chlorideresulted in the depreciation of cloud point temperature, rendering it to be advantageous interms of time and economy of the experiment. The optimized set of parameters facilitatedthe determination of trace amounts of nickel and the detection limit was calculated to be 12ng/L. The enrichment factor was found to be25. Besides analysis of differentwater samples, the proposed method was also successfully applied to determine nickel(â…¡)in certified reference material with satisfactory recoveries in the range of95-103%.In another experiment, Cd(â…¡) was successfully separated and enriched viacloud point extraction. The metal was allowed to make a hydrophobic complex with2-mercaptonicotinic acid which was later extracted into a miceller phase of Tween80.The pH was maintained at5to achieve high efficiency. The other parameters affectingthe extraction and analysis of Cd(â…¡) such as pH, ligand concentration,surfactant concentration, and the incubation time were also comprehensively studied andoptimized. In this experiment, the phase separation was achieved at rather lowertemperature due to the addition of NaF in miceller media. This method offered a very lowdetection limit (60ng/L) with a high precision (R.S. D2.5%) for cadmium. Theapplicability of this method was confirmed by analyzing certified reference material andwater samples with satisfactory results.For a highly selective removal of Pb(â…¡) from sediments, a new Pb(â…¡)-imprinted superparamagnetic mesoporous silica (SPMS) sorbent was synthesized andcharacterized by different techniques. The thiol functionalized SPMS offered a fastadsorption kinetics for Pb(â…¡) and equilibrium was achieved in just20min at pH8.0. Theadsorption isotherm data fits Langmuir model well with a maximum adsorption capacityof377.36mg g-1. The selectivity co-efficients of imprinted adsorbent for Pb(â…¡)/Bi(â…¡I)were3.05times higher than that of non-imprinted adsorbent. The imprinted adsorbentwas employed for the solid phase extraction of Pb(â…¡) and its detection by graphitefurnace atomic absorption spectrometry (GFAAS). The parameters affecting the determination of Pb(â…¡) were also well investigated and optimized. A linear relationshipbetween the Pb(â…¡) concentration and the absorbance was found in the range of50-900ng/L with a detection limit of15ng/L. The imprinted adsorbent was applied to thedetermination of Pb(â…¡) in two certified sediment samples with satisfactory results, whichindicates that Pb(â…¡)-imprinted superparamagnetic mesoporous silica adsorbent possesspromising features of a viable adsorbent for the preconcentration of Pb(â…¡) ions incomplex matrices.A new sorbent for solid phase extraction of Cu(â…¡) and Co(â…¡) was also synthesizedand characterized. Sulphonic acid functionalized magnetic mesoporous silica (MMS)was prepared by oxidation of thiol functionalized MMS. The newly synthesized sorbentwas applied for the solid phase extraction of Cu(â…¡) and Co(â…¡) prior to their analysis byGFAAS. The new material offered fast adsorption kinetics and the equilibrium data fittedwell to the Langmuir, Freundlich and Temkin adsorption isotherms. The experimentalmaximum adsorption capacity for Cu(â…¡) and Co(â…¡) was found to be132mg/g and99.1mg/g respectively. The linear working range for Cu(â…¡) and Co(â…¡) were found tobe70-400ng/L and85-350ng/L respectively with corresponding detection limits of20ng/L and27ng/L.