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Two liquid-phase microextraction procedures, single-drop microextraction (SDME) and dispersive liquid–liquid microextraction (DLLME), have been developed for the determination of lead by electrothermal atomic absorption spectrometry (ETAAS). Both methods were based on the formation of lead iodide-Rhodamine B complex which is in phosphoric acid medium. In the presence of KI, anionic lead iodide was complexed with Rhodamine B as an ion-association complex. Several factors that may be affected on the SDME and DLLME methods were optimized. In the optimum experimental conditions, the limit of detection (3s) and the enhancement factor were 0.008 μgL−1 and 152 for SDME and 0.0129 μgL−1 and 89 for DLLME respectively. The relative standard deviation (RSD) for eight replicate determinations of 0.25 μgL−1 Pb was 4.6% for SDME and 0.5 μgL−1 Pb was 2.9% for DLLME. The developed methods were validated by the analysis of certified reference materials, and applied successfully to the determination of lead in several water and food samples.
A comparative study was made with two HPLC columns of different lengths (PRP-X 100, 250 mm × 4.1 mm id and PRP-X 100, 100 mm × 4.1 mm id) coupled to HGAAS for the speciation of inorganic Sb(III) and Sb(V) species. The effects of eluent concentration and pH on the retention times of Sb species in both columns were investigated. The separation of Sb species was realized by using 50 mmol/L citrate solution at pH 4.0 as the eluent. The retention times were 2.0 min and 10.0 min in the 250 mm column, and 1.4 min and 3.6 min in the 100 mm column for Sb(V) and Sb(III) respectively. The hydrides were produced by adding 1% NaBH4 and 5.0 mol/L HCl solutions. The absorbance was linearly related to the Sb(V) concentration in the range 2.0-100 μg/L and to the Sb(III) concentration in the range 4.0-100 μg/L. The detection limits obtained for Sb(V) and Sb(III) were 1.0 and 0.8 μg/L respectively. Since certified standards for antimony in aqueous solutions are not currently available, the accuracy of the method was checked by the analysis of both species in several spiked water samples. The optimized experimental conditions were applied for the speciation and determination of the species in mining industry wastewaters.
Magnetic polymethylmethacrylate [mPMMA] microbeads (150-200 μm in diameter) carrying hexamethylene diamine (HMDA) were prepared for the removal of Pb(II) ions from aqueous solutions containing different amounts of Pb(II) ions (5–100 mg/L) and at different pH values (2.0–6.0). Adsorption rates were observed as high at the beginning of the adsorption process, and then equilibrium was reached in about 20 minutes. Adsorption of Pb(II) ions on the unmodified mPMMA microbeads was negligible (4.2 μmol/g). While HMDA-incorporation significantly increased the Pb(II) adsorption was (128 μmol/g). The adsorption of Pb(II) ions increased with an increasing pH, and reached a plateau value at around pH 5.0. The optimal pH range for Pb(II) removal was shown to be from 5.0 to 6.0. Desorption of Pb(II) ions was achieved using 0.1 M HNO3. The maximum desorption value was as high as 98%. These microbeads are suitable for repeated use for more than five adsorption-desorption cycles without a considerable loss of adsorption ca...
Competitive adsorption of the heavy metal ions Cu(II), Cd(II) and Pb(II) from aqueous media onto northern Anatolian smectites with a mean particle diameter of 200 mm, was investigated. The adsorption rate and capacity of the smectite for the selected heavy metal ions, containing different amounts of these ions (5-900 mg/L) at values ranging from pH 1.0 to 7.0 were studied. Very high adsorptions rates were observed at the beginning, and adsorption equilibria were then gradually achieved in about 30 minutes. The maximum adsorption of metal ions onto the smectite were found to be 41.46 mg Cd(II), 36.11 mg Pb(II) and 18.72 mg Cu(II) per gram of smectite. The order of affinity based on weight uptake by smectite was Cd(II)\( > \)Pb(II)\( > \)Cu(II). When the metal ions competed (in the case of adsorption from their mixture), the amounts of Cd(II), Pb(II) and Cu(II) ions adsorbed were 11.86 mg, 11.23 mg and 16.76 mg per gram of smectite, respectively. Desorption of the metal ions from smectite was studied in 0.5 M HNO\( 3 \) and very high desorption rates, greater than 95%, were achieved in all cases.
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