Solid phase extraction of trace amounts of palladium ions using multiwalled carbon nanotube modified by N,N’-bis(2-hydroxy-benzylidene)-2,2’(aminophenylthio) ethane prior to determination by flame atomic absorption spectrometry

Multiwalled carbon nanotubes modified with N,N’-bis(2-hydroxybenzylidene)-2,2’(aminophenylthio) ethane have been developed for the selective separation and/or preconcentration of trace amounts of Pd(II) in aqueous medium. Parameters including pH of aqueous solution, flow rates, the amount of ligand and the type of stripping solvents were optimized. It was found that the sorption is quantitative in the pH range (1.5-4), whereas quantitative desorption occurs instantaneously with 3.0 mL of 0.3 M Na2SO3. Linearity was maintained between 0.01 to 22 mg mL-1 for Pd in the final solution. The breakthrough volume was greater than 1800 mL with an enrichment factor of more than 600 and 6.0 mg L−1 detection limit (3s, n = 10). The effects of various ions interferences on the percent recovery of palladium ion were studied. The method was successfully applied to the determination of palladium ion in environmental samples. KEY WORDS: Multiwalled carbon nanotubes, Preconcentration, Palladium(II) determinationBull. Chem. Soc. Ethiop. 2012, 26(1), 19-26.DOI: http://dx.doi.org/10.4314/bcse.v26i1.

Synthesis of vanadium oxide nanoplates for electrochemical detection of amaranth in food samples

Amaranth dye is an organic compound largely used in the food and beverage industries with potential toxicity effects on humans. In this paper, a new electrochemical sensor used for the determination of amaranth in foods was reported, where a kind of V2O5 nanoplates (V2O5-NPs) was employed as electrode modifying materials. The V2O5 nanoplates modified electrode enhanced its electrochemical signal obviously in the determination of amaranth in foods and exhibited a wider linear response ranging from 0.1-270.0 µM with a low detection limit of 0.04 ± 0.001 µM (3Sb/m). This work offers a new route in developing new electrochemical sensors for the determination of colorant additives and other hazardous components in foods

Preconcentration of Trace Amounts of Pb(II) Ions without Any Chelating Agent by Using Magnetic Iron Oxide Nanoparticles prior to ETAAS Determination

This work investigates the potential of magnetic Fe3O4 nanoparticles as an adsorbent for separation and preconcentration of trace amounts of lead from water samples prior to electrothermal atomic absorption spectrometry (ETAAS) determination. No chemical modifier is required in graphite furnace. Pb(II) ion was adsorbed on magnetic Fe3O4 nanoparticles in the pH range of 5.5–6.5, and then magnetic nanoparticles (MNPs) were easily separated from the aqueous solution by applying an external magnetic field; so, no filtration or centrifugation was necessary. After extraction and collection of MNPs, the analyte ions were eluted using HNO3 1.0 mol L−1. Several factors that may affect the preconcentration and extraction process, such as pH, type, and volume of eluent, amount of MNPs, sample volume, salting out effect, and interference ions were studied and optimized. Under the best experimental conditions, linearity was maintained between 0.005–0.5 ng mL−1. Detection limits for lead were 0.8 ng L−1 based on 3Sb. The relative standard deviation of seven replicate measurements of 0.05 ng mL−1 of Pb(II) ions was 3.8%. Finally, the method was successfully applied to extraction and determination of lead ions in the water and standard samples

Combination of flame atomic absorption spectrometry with ligandless-dispersive liquid- liquid microextraction for preconcentration and determination of trace amount of lead in water samples

A new ligandless-dispersive liquid–liquid microextraction method has been developed for the separation and flame atomic absorption spectrometry determination of trace amount of lead(II) ion. In the proposed approach 1,2-dicholorobenzene and ethanol were used as extraction and dispersive solvents. Factors influencing the extraction efficiency of lead, including the extraction and dispersive solvent type and volume, pH of sample solution, concentration of chloride and extraction time were studied. Under the optimal conditions, the calibration curve was linear in the range of 7.0–6000 ng mL−1 of lead with R2 = 0.9992 (n = 10) and detection limit based on three times the standard deviation of the blank (3Sb) was 0.5 ng mL−1 in original solution. The relative standard deviation for eight replicate determinations of 1.0 mg mL-1 lead was ±1.6%. The high efficiency of dispersive liquid-liquid microextraction to carry out the determination of trace amounts of lead in complex matrices was demonstrated. The proposed method has been applied for determination of trace amounts of lead in water samples and satisfactory results were obtained. The accuracy was checked by analyzing a certified reference material from the National Institute of Standard and Technology, Trace elements in water (NIST CRM 1643e)

PVC-membrane potentiometric sensors based on a recently synthesized Schiff base for Fe(III) ion

A potentiometric iron sensor based on the use 3-(2-diethylamino-ethylimino)-1,3-dihydro-indol-2-one (DEDIO) as an ionophore in poly(vinyl chloride) (PVC) matrix, is reported. The plasticized membrane sensor exhibits a Nernstian response for Fe(III) ions over a wide concentration range (2.0 × 10-6 - 5.0 × 10-2 M) with a super Nernstian slope of 26(plus or minus 1) mV per decade. It has a fast response time of less than 12 s and can be used for ten weeks without any considerable divergences in its potentials the electrode can be used in the pH range 4.5-8.0. The proposed sensor shows fairly good discriminating ability towards Fe(III) ion in comparison with a large number of alkali, alkaline earth, transition and heavy metal ions. The sensor was used as indicator electrode in potentiometric titration of Fe(III) ions vs. EDTA.DOI: http://dx.doi.org/10.4314/bcse.v26i1.

Synthesis of cellulose acetate nanofibers and its application in the release of some drugs

Objective(s): The purpose of this study was to compare novel sandwich-structured nanofibrous membranes, and coaxial and usual methods, to provide sustained-release delivery of morphine for drug delivery. In this work, synthesis ofnanofibrous cellulose acetate (NFC) was carried out by electrospinning. Methods: A weighed amount of cellulose acetate (CA) powder was dissolved in 3:1 v/v acetone/dimethylformamide (DMF) to obtain a CA solution at a concentration of 8 to16% w/v. Acetaminophen or morphine-loaded CA solutions were prepared by dissolving CA powder and Acetaminophen (A) or morphine in the weight ratio of 5:1, in an acetone/DMF mixture. Under optimum condition, they were electrospun into sandwich structured membranes with the coaxial method and cellulose acetate as the surface layer and cellulose acetate/drugs as the core. Results: Characterization of the radius of fiber is shown as 52.9 ± 0.1nm with scanning electron microscopy (SEM). The full range drug release profiles of nanofibers are shown as 80.7% of the contained drug in 8h. The drug release from nanofiber was controlled through a typical Fickian diffusion mechanism from the cellulose acetate matrix by a release exponent value of 0.24 for conventional nanofiber, 0.35 for coaxial nanofiber and 0.40 (less than 0.45) for sandwich nanofibers. Conclusions: All the cellulose acetate nanofibers showed that they could release large amounts of drugs in vitro for more than one day. However, among these three methods, the best one is a sandwich method because its release is slower than that of the other methods