Magda Ali Akl

Preconcentration and separation of total mercury in environmental samples using chemically modified chloromethylated polystyrene-PAN (ion-exchanger) and its determination by cold vapour atomic absorption spectrometry

The use of chemically modified chloromethylated polystyrene-PAN, CMPS-PAN (ion-exchanger) for the preconcentration and separation of total mercury after digestion in preparation for determination by cold vapour atomic absorption spectrometry (CVAAS) was described. The effects on the percentage of recovered mercury by mass change of ion-exchanger, stirring time, pH of the solution samples and eluent concentration were studied. The distribution coefficient K(d) is 10(6.6) ml g(-1). The interfering effects of some foreign ions were described. The metal complex formed between CMPS-PAN ion-exchanger and mercury was characterized by IR spectroscopy, pH-metric titration and thermal analysis. The method is simple and rapidly applicable for the determination of total mercury (ng ml(-1)) in natural water, milk and urine.

Preconcentration extractive separation, speciation and spectrometric determination of iron(III) in environmental samples

Abstract Preconcentration, speciation and separation with solvent extraction of Fe(III) from samples of different origin, using methyl isobutyl ketone (MIBK) as a solvent and the sodium salt of 2-carboethoxy-1,3-indandione (CEIDNa) as a complexing agent for Fe(III), were studied. CEIDNa reacts with Fe(III) in the pH range 1.5–3.5 to produce a red colored complex of Fe(III)–CEIDNa (1:3 molar ratio) soluble in MIBK. The investigation includes a study of the characteristics that are essential for solvent extraction, spectrophotometric and flame atomic absorption spectrometric determination (AAS) of iron. A highly sensitive, selective and rapid spectrometric method is described for the trace analysis of iron(III) by CEIDNa. The complex formed obeys Beers law from 0.06 to 1.8 mg l −1 with an optimum range. A single step extraction was efficiently used with a distribution ratio ( D )=10 3.6 . The extracted red colored (1:3) Fe–CEIDNa was measured spectrophotometrically at 500 nm with a molar absorptivity of 1.2×10 4 l mol −1 cm −1 . In addition, the organic phase was directly aspirated to the flame for AAS determination and the signals related to Fe(III) concentration were recorded at 243.3 nm. The complexation of iron(III) with CEIDNa allows the separation of the analyte from alkali, alkaline earth and other elements, which are not complexed. The proposed preconcentration procedure was applied successfully to the determination of trace Fe(III) in soil, milk and natural water samples.

Validation of an HPLC-UV method for the determination of ceftriaxone sodium residues on stainless steel surface of pharmaceutical manufacturing equipments

In pharmaceutical industry, an important step consists in the removal of possible drug residues from the involved equipments and areas. The cleaning procedures must be validated and methods to determine trace amounts of drugs have, therefore, to be considered with special attention. An HPLC-UV method for the determination of ceftriaxone sodium residues on stainless steel surface was developed and validated in order to control a cleaning procedure. Cotton swabs, moistened with extraction solution (50% water and 50% mobile phase), were used to remove any residues of drugs from stainless steel surfaces, and give recoveries of 91.12, 93.8 and 98.7% for three concentration levels. The precision of the results, reported as the relative standard deviation (RSD), were below 1.5%. The method was validated over a concentration range of 1.15-6.92 μg ml(-1). Low quantities of drug residues were determined by HPLC-UV using a Hypersil ODS 5 μm (250×4.6 mm) at 50 °C with an acetonitrile:water:pH 7:pH 5 (39-55-5.5-0.5) mobile phase at flow rate of 1.5 ml min(-1), an injection volume of 20 μl and were detected at 254 nm. A simple, selective and sensitive HPLC-UV assay for the determination of ceftriaxone sodium residues on stainless steel surfaces was developed, validated and applied.

Spectrophotometric determination of phosphate with alizarin red sulphonate

Abstract The formation of complexes between orthophosphate and alizarin red sulphonate (ARS) has been ascertained. One or two kinds of complexes are formed in solution according to the pH of the medium with PO3−4:ARS ratios of 1:3 and 1:2 at pH 6.6 and 8.3 with formation constants of 2.97 × 1020 and 1.3 × 109 at λmax 478 and 520 nm, respectively. The development of the 1:3 complex was utilized for the determination of orthophosphate with a working concentration range of 0.03–6.00 μg ml−1 phosphorus (ϵ = 1.14 × 104 l mol−1 cm−1 at 478 nm). The interference of some anions and cations was investigated. Structures of the isolated solid complexes are suggested based on elemental analysis and infrared spectrophotometric measurements. A procedure for the determination of different forms of phosphorus has been elaborated and applied to differentiate between non-organic and organically bound phosphorus in re-used water effluents.

Application of Crosslinked Ionic Poly(Vinyl Alcohol) Nanogel as Adsorbents for Water Treatment

Core-shell smart ionic nanogels based on poly(vinyl alcohol) (PVA) core and poly(N-isopropylacrylamide/acrylic acid) p(NIPAm-AAc) shell particles were successfully synthesized through a one-step surfactant-free emulsion polymerization method (SFEP). Different mole ratios of p(NIPAm-AAc) shells were synthesized. The morphologies of PVA/p(NIPAm-AAc) nanogels were investigated by transmission electron microscope (TEM). The data showed the formation of spherical nanoparticles and well-defined core-shell nanogels. PVA/p(NIPAm-AAc) core-shell nanogels were applied as a novel polymeric adsorbent to remove heavy metal pollutants from aqueous solution. Copper(II) (Cu2+) ions were selected as the target pollutant to evaluate these nanoparticles’ adsorption capability. The influence of the uptake conditions such as pH, weight ratio of nanoparticles, time, initial feed concentration, and adsorption temperature on the metal ion binding capacity of nanogels was also tested. Adsorption equilibrium data were calculated according to Langmuir and Freundlich isotherms. It was found that the sorption of Cu2+ was better suited to the Freundlich adsorption model than the Langmuir adsorption model. Also, the selectivity of the nanogels toward the different metal ions such lead (Pb2+) and cadmium (Cd2+) were tested. The maximum of Cu2+ ions adsorbed on to PVA/p(NIPAm-AAc) core-shell nanogels adsorbent was 94 mg/g obtained under simple and fast experimental conditions, indicating these nanogels can be used as effective and practical polymeric adsorbents.

Removal of Iron and Manganese in Water Samples Using Activated Carbon Derived from Local Agro-Residues

Three olive stones-derived activated carbons (ACOS) with different chemical characteristics, appropriate for the removal of iron and manganese in groundwater are prepared. The steam activated carbon is obtained from carbonized olive stones in the presence of nitrogen in the temperature range from 700 to 900°C and modified by HNO3 and ammonium persulphate. The structure of the activated carbons was characterized by N2 adsorption at 77 K, scan electron microscopy and FTIR. B.E.T and α-methods are used to deduce the effective surface areas. The parameters (such as initial pH, temperature, etc) affecting the adsorption capacity of ACOS toward iron and manganese cations removal from aqueous solutions are investigated using batch experiments. The study of kinetic models including pseudo first order and pseudo second-order are carried out. Langmuir adsorption isotherm is investigated. Equilibrium adsorption data fitted the Langmuir adsorption isotherm well with R2>0.9908. The maximum adsorption capacities of ACOS for the removal of iron and manganese cations are calculated. The results obtained revealed that the sample activated by HNO3 has the highest adsorption capacity followed by ammonium persulphate and steam activated samples. The mechanism of adsorption is proposed.

Superparamagnetic Core-Shell Polymeric Nanocomposites for Efficient Removal of Methylene Blue from Aqueous Solutions

Ultrafine well-dispersed Fe3O4 magnetic nanoparticles (NPs) were directly prepared in an aqueous solution using controlled co-precipitation method. The Fe3O4-poly(acrylamide-co-sodium acrylate) core-shell magnetic nanogels are prepared by solution polymerization of acrylamide (AM) and sodium acrylate (AA-Na) monomers in the presence of Fe3O4 NPs, N,N′-methylenebisacrylamide (MBA) as a cross-linker, N,N,N′,N′-tetramethylethylenediamine and potassium peroxydisulphate (KPS) as the redox initiator system. The novel Fe3O4-poly(acrylamide-co-sodium acrylate) core-shell magnetic nanocomposite hydrogels are prepared by in situ free radical co-polymerization of AM and AA-Na in an aqueous dispersion of nanogel particles using MBA as the cross-linker and KPS as the initiator. The as-prepared nanocomposite hydrogels are characterized by Fourier transform infrared spectroscopy spectra, X-ray powder diffraction and transmission electron microscopic measurements. The mean particle size of the synthesized magnetite (Fe3O4) NPs was approximately 8 nm. The diameter of the stabilized polymer-coated Fe3O4 nanogels is approximately 11 nm. The surface morphology of the nanocomposites has been studied by scanning electron microscopy and atomic force microscopy. The Fe3O4-poly(acrylamide-co-sodium acrylate) nanocomposites have been extensively investigated for the removal of basic dyes from aqueous solutions. Results of batch experiments showed that these adsorbents exhibited high sorption capacities towards methylene blue (MB). Experimental data were analyzed using first-order kinetics, pseudo-second-order kinetics and intra-particle diffusion models. The kinetics followed a pseudo-second-order equation. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich equations. The thermodynamic parameters for the adsorption of MB onto the nanocomposite hydrogels were also calculated. Regeneration of nanocomposite adsorbents can be easily achieved.

Simultaneous preconcentration flotation-separation and spectrophotometric determination of thorium, lanthanum and yttrium in some geological and enviromental samples

The extraction and preconcentration of a metal complex via surfactant-mediated phase separation was studied. A sensitive, selective and low-cost methodology for the determination of micro amounts of thorium, lanthanum and yttrium ions, using Eriochrome Cyanine R (ECR) with a flotation step prior to spectrophotometric determination was developed. The precipitate in the scum layer was quantitatively collected, stripped with 4 ml of 3% HCl and measured spectrophotometrically at 540 nm for Th(IV) and at 650 nm for both La(III) and Y(III). The stripping of Th(IV), La(III) and Y(III) from the scum layer was carried out in one step with different mineral acids. The stripping efficiency was found to be quantitative in the case of HCl. An excess amount of ECR was used to eliminate the interfering effects of various foreign species. The proposed procedure was applied to the determination of Th(IV), La(III) and Y(III) spiked in natural water samples and in some ore samples. Additionally, the mechanism of flotation of the metal chelate was proposed to be due to a physical interaction between the metal chelate and the oleic acid surfactant through the Van der Waals force.

USE OF ERIOCHROME CYANINE R FOR SEPARATION-FLOTATION AND MICRODETERMINATION OF HAFNIUM AND ZIRCONIUM IN REAL SAMPLES

Eriochrome cyanine R (ECR) is investigated as a collector for separation and flotation of hafnium from zirconium through the use of an oleic acid surfactant. Selective separation of Zr(IV) is achieved at pH 2 with maximum efficiency, whereas Hf(IV) is completely separated at pH 7.0–7.5. Excess ECR is used to avoid interferences from foreign ions without any effect on the separation efficiency. The procedure is successfully applied to the determination of Zr(IV) and Hf(IV) in real samples. A flotation mechanism is proposed.

Flotation and Spectrophotometry : Thorough Investigation and Application to the Determination of the Total Amounts of Lanthanum and Yttrium in Natural Samples

The extraction and preconcentration of a metal complex via surfactant-mediated phase separation was studied. A sensitive, selective and low-cost methodology for the determination of microamounts of Lanthanum and Yttrium, using alizarin red sulfonate (ARS) with a flotation step prior to absorptiometric determination was developed. The precipitate in the scum layer was quantitatively collected, stripped with 10% HNO3 and measured by spectrophotometry at 650 nm. Stripping of La(III) and Y(III) from the scum layer was carried out in one step with different mineral acids. The stripping efficiency was found to be quantitative in the case of HNO3. Excess ARS was used to nullify the interfering effects of various foreign species. The proposed procedure has been applied to the determination of La and Y spiked in natural water samples and real ore samples. Additionally, the mechanism of flotation of the metal chelate was proposed to be due to a physical interaction between the metal chelate and the oleic acid surfa...