A micro mixed micelle-mediated preconcentration procedure for spectrophotometric determination of uranium in real and synthetic samples

A critical review of selected preconcentration techniques used for selenium determination in analytical samples

Selenium (Se) is considered to be an essential trace element needed for all living organisms. The importance, deficiency, and toxic effects of Se mainly depend on its quantity and chemical nature. It has been observed that the inorganic versions of Se are more hazardous than the organic versions. This review is mainly focused on the application of different extraction methods used for Se extraction and determination such as microextraction, solid-phase extraction (SPE), and their modified modes in the last 12 years. The use of different dispersive medium (magnetic field, ultrasonic radiation, and vortex agitator) to enhance Se separation is also part of this review. The usage of environmentally friendly solvents such as supramolecular solvents, hydrophobic deep eutectic solvents (DESs), and ionic liquids (ILs) are also the focus of attention in this review. This review is also emphasized the application of advanced microextraction methods, particularly liquid-phase microextraction (LPME). The most recent advances in LPME extraction techniques for Se in various environmental samples, as well as their prospects, are reviewed. Additionally, a summary of cheap, simple, and accurate techniques that have not yet been used to determine small amounts of Se has been provided.

Air-assisted cloud point extraction coupled with inductively coupled plasma optical emission spectroscopy for determination of samarium in environmental samples

For the first time, air-assisted cloud point extraction (AACPE) was presented to preconcentrate metal ions. The procedure was conjugated with inductively coupled plasma-optical emission spectroscopy for determination of samarium. In this procedure, samarium ions were complexed with aluminon and extracted into Triton X-114 in the presence of potassium iodide. The mixture was repeatedly sucked and dispersed with a syringe (three times) to create cloud solution. Experimental factors that affect the extraction competence of the AACPE procedure, such as pH, amount of aluminon and Triton X-114, salt addition, number of suction/injection cycles, and centrifugation rate and time, have been investigated and optimized. A linear calibration curve from 0.2 to 200.0 μg L−1 with enrichment factor and detection limit of 102 and 0.06 μg L−1, respectively, was established under the optimum experimental conditions. The approach was used to determine samarium in wastewater and rock samples, with recoveries ranging from 98% to 99%.

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A novel CPE procedure by oil-in-water microemulsion for preconcentrating and analyzing thorium and uranium

A novel cloud point extraction (CPE) procedure was developed to preenrich Th4+ and UO2 2+ by oil-in-water (O/W) microemulsion. Coupling CPE to ICP-MS, the separation and analysis were achieved at a trace level, in which the low detection limits were 0.019 and 0.042 ng mL−1 for Th(IV) and U(VI), respectively. N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), as an extremely hydrophobic extractant, was failed to dissolve in single or mixed micelles, but was successfully solubilized to CPE system owing to O/W microemulsion. The extraction efficiency and selectivity for Th4+ and UO2 2+ were excellent under acidic condition of 1.0 mol L−1 HNO3, and the recovery of ultra-trace Th4+ and UO2 2+ was almost 100% even at the presence of large amounts of lanthanides, exhibiting high tolerance limits for lanthanides. The solubilization, extraction and coordination behaviours were studied systematically via DLS, UV–vis, 1H NMR and FT-IR. Moreover, the solubilization of N,N′-dioctyl-N,N′-dioctyl-2,9-diamide-1,10-phenanthroline (Oct-Oct-DAPhen) and efficient extraction for UO2 2+ were also realized by O/W microemulsion, which further proved the feasibility of the method.

Preparation of lactic acid modified cellulose nanoparticles by microwave heating for preconcentration of copper from blood and food samples

In this study, nano-sized cellulose modified with lactic acid (MW-Ce-LA) was prepared with the assistant of microwave then used for the adsorption of Cu²⁺ from real samples. This modified cellulose was characterized by means of FTIR, TEM, XRD, and elemental analysis. ICP-OES was used for determination of Cu²⁺. The effect of pH, adsorption times, temperature, sorbent dose, and initial adsorbate concentration were studied to detect the ideal adsorption condition. Langmuir model proved to be the best to fit the adsorption isotherm experiments with maximum adsorption capacity of 90.3 mg g^-1 Cu²⁺. Calculated thermodynamic parameters (ΔG° and ΔH°) for adsorption of Cu²⁺ on MW-Ce-LA suggested exothermic and nonspontaneous character of the adsorption process. The reusability tests indicated regeneration of the prepared adsorbent simply using 1 mol L^-1 of HCl. The examined method was used effectively to preconcentrate Cu²⁺ from water, blood, and food samples.

A study on the preparation and application of a core-shell surface imprinted uranyl magnetic chelating adsorbent

A core-shell surface imprinted uranyl magnetic chelating adsorbent (UMCA) was synthesized by combining the sol-gel process with the surface molecular imprinting technique (SMIT). A specific salophen and uranyl-salophen were designed and synthesized. Then, the synthesized uranyl-salophen complex was used as a template (in which uranyl is the target analyte), 3-aminopropyltriethoxysilane as a functional monomer and tetraethylorthosilicate as a cross-linker. The obtained UMCA was characterized by a variety of modern analytical and detection techniques. The adsorbent can be used for the solid-phase extraction of uranyl with good selectivity, high adsorption capacity, magnetic separation characteristics and good reusability. The chelating sorbent was successfully applied for the separation of uranyl, followed by multiphase photocatalytic resonance fluorescence method determination in several environmental water samples with a relative standard deviation of <5.48% and spiked recoveries of 92.5% to 103.0%. The adsorption mechanism was preliminarily discussed.