Chemically modified activated carbon with 1-acylthiosemicarbazide for selective solid-phase extraction and preconcentration of trace Cu(II), Hg(II) and Pb(II) from water samples

A new sorbent 1-acylthiosemicarbazide-modified activated carbon (AC-ATSC) was prepared as a solid-phase extractant and applied for removing of trace Cu(II), Hg(II) and Pb(II) prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 3, the maximum static adsorption capacity of Cu(II), Hg(II) and Pb(II) onto the AC-ATSC were 78.20, 67.80 and 48.56 mg g⁻¹, respectively. The adsorbed metal ions were quantitatively eluted by 3.0 mL of 2% CS(NH₂)₂ and 2.0 mol L⁻¹ HCl solution. Common coexisting ions did not interfere with the separation. According to the definition of IUPAC, the detection limits (3σ) of this method for Cu(II), Hg(II) and Pb(II) were 0.20, 0.12 and 0.45 ng mL⁻¹, respectively. The relative standard deviation under optimum conditions is less than 4.0% (n = 8). The prepared sorbent was applied for the preconcentration of trace Cu(II), Hg(II) and Pb(II) in certified and water samples with satisfactory results.     

Polypyrrole‐modified magnetic nanoparticles and high‐performance liquid chromatography for determination of glibenclamide from biological fluids

In this research, the successful application of polypyrrole (PPy)‐modified magnetic nanoparticles (NPs) is described as an efficient adsorbent for the extraction and the preconcentration of glibenclamide (GB). To measure it in biological fluids samples, HPLC‐UV detection was used. First, iron oxide NPs were prepared by coprecipitation procedure and then their surface was modified by PPy monomers. Characteristics of Fe₃ O₄ @PPy NPs were investigated by FTIR technique and NP size studied with scanning electron microscopy. The vibrating sample magnetometer was used to characterise the magnetic properties of the prepared modified NPs. The affecting parameters in extraction including analyte sorption time, analyte desorption time, ionic strength, sample volume, pH, eluent type, eluent amount, and amount of Fe₃ O₄ @PPy NPs were investigated and optimised. The linear range of the proposed method is 0.2–700.0 μg l⁻¹ and the limit of detection is 0.1 μg l ^{− 1}. The relative standard deviation for five replicate analyses was 3.9. Finally, the proposed procedure was successfully employed for preconcentration and determination of GB in biological fluids.Inspec keywords: nanofabrication, pH, nanomagnetics, desorption, iron compounds, chromatography, adsorption, spectrochemical analysis, nanoparticles, magnetic particles, scanning electron microscopy, Fourier transform infrared spectraOther keywords: polypyrrole‐modified magnetic nanoparticles, high‐performance liquid chromatography, glibenclamide, preconcentration, biological fluids samples, HPLC‐UV detection, iron oxide NPs, coprecipitation procedure, PPy monomers, scanning electron microscopy, vibrating sample magnetometer, magnetic properties, analyte desorption time, analyte sorption time, biological fluids     

Simultaneous trace multielement determination by ICP-OES after solid phase extraction with modified octadecyl silica gel

Multielement simultaneous determination of 35 trace elements in environmental samples was carried out by inductively coupled plasma emission spectrometry (ICP-OES) after preconcentration with octadecyl silicagel, modified with aurin tricarboxylic acid (Aluminon). Optimal experimental conditions including pH of sample solution, sample volume, sample and eluent flow rate, type, concentration and volume of eluent and foreign ions effect were investigated and established.Trace element ions in aqueous solution were quantitatively adsorbed onto octadecyl silicagel modified with aurin tricarboxylic acid at pH 8.0 with a flow rate of 11.0 mL min⁻¹. The adsorbed element ions were eluted with 3–5 mL of 0.5 mol L⁻¹ HNO₃ at a flow rate of 10.0 mL min⁻¹ and analyzed by ICP-OES simultaneously.The proposed method has at least preconcentration factor of 100 in water samples, which results high sensitive detection of ultra-trace and trace analysis. The present methodology gave recoveries better than 70% and RSD less than 16%.     

Acylisoxazolone-impregnated Si-MCM-41 mesoporous materials as promising liquid-solid extractants of metals

The solid-liquid extraction of Cu(II) from 0.33 M (Na⁺, H⁺)SO₄²⁻ sulphate medium at 25 °C by calcined mesoporous materials type Si-MCM-41, impregnated by the acidic extractant 3-phenyl-4-benzoyl-isoxazol-5-one (HPBI), has been tested. The Si-MCM-41 material was impregnated by HPBI using the dry impregnation method. It was characterized by physico-chemical methods: N₂-sorption, XRD, SEM and determination of the amount of HPBI in the solid. The extraction rate was determined as a function of pH and extractant concentration in the material. The extraction of Cu(II) into impregnated mesoporous material can reach 99%.     

Determination of cadmium at ultra-trace levels by CPE–molecular fluorescence combined methodology

A highly sensitive micelle-mediated extraction methodology for the preconcentration and determination of trace levels of cadmium by molecular fluorescence has been developed. Metal was complexed with o-phenanthroline (o-phen) and eosin (eo) at pH 7.6 in buffer Tris medium and quantitatively extracted into a small volume of surfactant-rich phase of PONPE 7.5 after centrifugating. The chemical variables affecting cloud point extraction (CPE) were evaluated and optimized. The RSD for six replicates of cadmium determinations at 0.84 μg L⁻¹ level was 1.17%. The linearity range using the preconcentration system was between 2.79 × 10⁻³ μg L⁻¹ and 2.81 μg L⁻¹ with a correlation coefficient of 0.99. Under the optimal conditions, it obtained a LOD of 8.38 × 10⁻⁴ μg L⁻¹ and LOQ of 2.79 × 10⁻³ μg L⁻¹. The method presented good sensitivity and selectivity and was applied to the determination of trace amounts of cadmium in commercially bottled mineral water, tap water and water well samples with satisfactory results. The proposed method is an innovative application of CPE-luminescence to metal analysis comparable in sensitivity and accuracy with atomic spectroscopies.     

Spectrophotometric determination of Sb(III) and Sb(V) in biological samples after micelle-mediated extraction

This work presents a micelle-mediated extraction method for simultaneous preconcentration and determination of Sb(III) and Sb(V) species in biological samples as a prior preconcentration step to their spectrophotometric determination. The analytical system is based on the selective reaction between Sb(III) and bromopyrogallol red (BPR) in the presence of cetyltrimethylammonium bromide (CTAB) and potassium iodide at pH 6.4. Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of potassium iodide and ascorbic acid. The optimal extraction and reaction conditions were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor, and improvement factors) were obtained. Linearity for Sb(III) and Sb(V) were obeyed in the range of 0.2–20.0 ng mL⁻¹ and 0.4–25.0 ng mL⁻¹, respectively. The detection limit for the determination of Sb(III) and Sb(V) were 0.05 ng mL⁻¹ and 0.08 ng mL⁻¹, respectively. The interference effect of some anions and cations was also studied. The method was applied to the determination of Sb(III) in the presence of Sb(V) and total antimony in blood plasma and urine samples.     

Cr(VI) sorption behavior from aqueous solutions onto polymeric microcapsules containing a long-chain quaternary ammonium salt: Kinetics and thermodynamics analysis

This work studies the adsorption of Cr(VI) ions from an aqueous acid solution on hydrophobic polymeric microcapsules containing a long-chain quaternary ammonium salt-type extractant immobilized in their pore structure. The microcapsules were synthesized by adding the extractant Aliquat 336 during the in situ radical copolymerization of the monomers styrene (ST) and ethylene glycol dimethacrylate (EGDMA). The microcapsules, which had a spherical shape with a rough surface, behaved as efficient adsorbents for Cr(VI) at the tested temperatures. The results of kinetics experiments carried out at different temperatures showed that the adsorption process fits well to a pseudo-second-order with an activation energy of 82.7 kJ mol⁻¹, confirming that the sorption process is controlled by a chemisorption mechanism. Langmuir's isotherms were found to represent well the experimentally observed sorption data. Thermodynamics parameters, namely, changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰), are also calculated. The results indicate that the chemisorption process is spontaneous and exothermic. The entropy change value measured in this study shows that metal adsorbed on microcapsules leads to a less chaotic system than a liquid–liquid extraction system.     

Sorption behavior of nano-TiO2 for the removal of selenium ions from aqueous solution

Titanium dioxide nanoparticles were employed for the sorption of selenium ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption was found to be fast, and to reach equilibrium basically within 5.0 min. The sorption has been optimized with respect to the pH, maximum sorption has been achieved from solution of pH 2–6. Sorbed Se(IV) and Se(VI) were desorbed with 2.0 mL 0.1 mol L⁻¹ NaOH. The kinetics and thermodynamics of the sorption of Se(IV) onto Nano-TiO₂ have been studied. The kinetic experimental data properly correlate with the second-order kinetic model (k₂ = 0.69 g mg⁻¹ min⁻¹, 293 K). The overall rate process appears to be influenced by both boundary layer diffusion and intraparticle diffusion. The sorption data could be well interpreted by the Langmuir sorption isotherm. The mean energy of adsorption (14.46 kJ mol⁻¹) was calculated from the Dubinin–Radushkevich (D–R) adsorption isotherm at room temperature. The thermodynamic parameters for the sorption were also determined, and the ΔH⁰ and ΔG⁰ values indicate exothermic behavior.     

Synthesis, characterization and in vitro cytotoxicity of self-regulating magnetic implant material for hyperthermia application

Gd-substituted zinc ferrite nanoparticles with low Curie temperatures (T_c) were synthesized by a chemical co-precipitation method. The magnetic properties and heat generation characteristics of these magnetic nanoparticles were investigated. The T_c of ZnGd_xFe_2 − xO₄ nanoparticles increased with increasing Gd³⁺ substitution, and was ~ 318 K at x = 0.02, which was a suitable Curie temperature for thermal seeds implanted in human body. The study on heat generation ability under external alternating magnetic field showed that the temperatures of these nanoparticles could be safely controlled around T_c without the temperature probe and controller. Furthermore, in vitro cytotoxicity of the ferrite nanoparticles was assessed using MTT assay. The results demonstrated that exposure to the bare ferrite nanoparticles for 48 h resulted in concentration-dependent toxicity. Cell growth inhabitation was observed when 4.0 mg/ml of bare ferrite nanoparticles was used. In contrast, PEG-capped nanoparticles had no significant effect on cell viability at any of the concentrations tested.     

DC resistivity of Ni–Zn ferrites prepared by oxalate precipitation method

Polycrystalline ferrites with general formula Ni_1−xZn_xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were prepared by oxalate precipitation method. The samples were characterized by X-ray diffraction (XRD), IR and scanning electron microscope (SEM) techniques. All compositions show cubic Spinel structure. Lattice constant increases with increase in zinc content, obeying Vegard's law. The physical densities are about 98.14% of their X-ray density. Average crystallite size lies in the range 27.59–31.49 nm. Infrared studies show two absorption bands near about 400 cm⁻¹ and 600 cm⁻¹ for octahedral and tetrahedral sites, respectively. The resistivity of all the samples was studied. It is observed that the resistivity of nickel–zinc ferrites prepared by oxalate precipitation method is higher than that prepared by ceramic and citrate precursor method. It is attributed to greater homogeneity and smaller grain size. Activation energy in paramagnetic region is higher than that of ferrimagnetic region.