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-phase extraction (SPE) techniques [ 16 – 18 ]. However, LLE and SPE are usually expensive and time-consuming methods and require large quantities of samples and toxic organic solvents. Cloud-point extraction (CPE) is a fast, simple, green, and efficient

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Abstract  

A cloud point extraction method followed by inductively coupled plasma-mass spectrometry (ICP-MS) has been developed for the detection of trivalent lanthanides (Ln(III)) in aqueous samples. Ammonium pyrrolodinedithiocarbamate (APDC) was used as the chelating ligand with 2 wt% Triton X-114 as the surfactant. Various experimental parameters were investigated and the extraction efficiency, distribution ratios and concentration factors for the extraction of lanthanum (La), neodymium (Nd), europium (Eu) and thulium (Tm) were determined.

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Methods for the simultaneous preconcentration of lanthanides by cloud point extraction and their determination using neutron activation analysis have been developed. The preconcentration method involves the use of a nonionic surfactant and a chelating agent. A fairly small volume of surfactant-rich phase was obtained under optimized experimental conditions, leading to detection limits between 0.3 and 3.0 ng . g-1. Critical parameters that influence extraction efficiency were solution pH and concentration of chelating agent, and to a lesser extent, ionic strength and temperature. Most of the chelates were quantitatively extracted (>90%) at high pH values. Selective separation can be achieved by varying some of the experimental conditions.

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The aim of this study is the separation and pre-concentration of thorium from aqueous solutions by cloud point extraction (CPE) and its the radiometric determination by liquid scintillation counting (LSC). For CPE, tributyl phosphate (TBP) was used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The radiometric measurements were performed after phase separation by mixing of the surfactant phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, ionic strength (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca2+ and Fe3+ ions, and humic acid colloids) on the CPE separation recovery have been investigated at constant reactant ratio (m(TBP)/m(Triton) = 0.1). According to the experimental results the maximum chemical recovery is (60 ± 5)% at pH 3. Regarding the other parameters, generally Ca2+ and Fe3+ ions as well as the presence of colloidal species in solution (even at low concentrations) results in significant decrease of the chemical recovery of uranium. On the other hand increasing NaCl concentration leads to enhancement of chemical recovery. Generally, the method could be applied successfully for the radiometric determination of thorium in water solutions with relatively increased thorium content.

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Abstract  

The aim of this study is the radiometric determination of uranium in waters by liquid scintillation counting (LSC) after pre-concentration of the element by cloud point extraction (CPE). For CPE, tributyl phosphate (TBP) is used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The measurement is performed after phase separation by mixing of the surfactant phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, reactant ratio (e.g. m(TBP)/m(Triton), ionic strength (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca2+ and Fe3+ ions as well as humic acid and silica colloids) on CPE has been investigated. According to the experimental results the total method efficiency is (13 ± 2)% and the chemical recovery (50 ± 10)% at pH 4 and reactant ratio (V(TBP)/V(Triton) = 0.1). Regarding the other parameters, generally Ca2+ and Fe3+ ions as well as the presence of colloidal species in solution (even at low concentrations) results in significant decrease of the chemical recovery of uranium. On the other hand increasing NaCl concentration leads to enhancement of chemical recovery. The detection limit under optimum experimental conditions has been found to be 0.5 Bq L−1 indicating that the method could be applied only to waters samples with increased uranium concentration. Moreover, the negative effect of the chemical species found in natural waters limits the applicability of the method with the respect to environmental radioactivity measurements.

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A method for the preconcentration of Cu(II) by cloud point extraction (CPE) followed by its determination using neutron activation analysis (NAA) was developed. The method involves the use of a nonionic surfactant, namely PONPE-7.5, and a chelating agent 1-(2-pyridylazo)-2-naphthol (PAN). The phase diagram of the surfactant was constructed and the effects of different additives on the cloud point were investigated. Factors, such as the solution pH, ionic strength, temperature, and concentrations of chelating agent and surfactant, which can influence the extraction efficiency of the metal, were optimized. The copper(II) chelate was extracted into a surfactant-rich phase of small volume with a recovery of nearly 100% and a preconcentration factor of 60. The small volume of the surfactant-rich phase obtained complies with the green chemistry concept, allowing the design of extraction procedures having lower toxicity than those using organic solvents. The method was applied to tap water samples.

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The increasing application of biobased lubricants could significantly reduce environmental pollution and contribute to the replacement of petroleum base oils. Vegetable oils are recognized as rapidly biodegradable and are thus promising candidates for use as base fluids in formulation of environment friendly lubricants. Although many vegetable oils have excellent lubricity, they often have poor oxidation and low temperature stability. Here in, we report the lubricant potential of Moringa oil, which has 74% oleic acid content and thus possess improved oxidation stability over many other natural oils. For comparison, Jatropha oil, cottonseed oil, canola oil and sunflower oil were also studied. Among these oils, Moringa oil exhibits the highest thermo-oxidative stability measured using PDSC and TG. Canola oil demonstrated superior low temperature stability as measured using cryogenic DSC, pour point and cloud point measurements. The friction and wear properties were measured using HFRR. Overall, it was concluded that Moringa oil has potential in formulation of industrial fluids for high temperature applications.

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Surfactant enhanced non-classical extractions are presented and discussed. They include micellar enhanced ultrafiltration and cloud point extraction. The ideas of the processes are given and the main features are presented. They are compared to the classical solvent extraction. The fundamental of micellar solutions and their solubilisation abilities are also discussed.

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A micelle-mediated extraction (CPE) procedure has been developed to remove trace amounts of uranium from wastewater using a non-ionic surfactant (Triton (X-100)) and lipophilic chelating extracting agent (D2EHPA) in acetate medium. The methodology used is based on the formation of metal complexes soluble in a micellar phase of a non-ionic surfactant. The uranyl ions complexes are then extracted into the surfactant-rich phase at a ambient temperature. The effects of different operating parameters such as the concentrations of Triton (X-100), D2EHPA and metal ions, temperature, sodium acetate rate and pH on the cloud point extraction of uranyl ions were studied in details and a set of optimum conditions were obtained. The results showed, without contribution of energy (ambient temperature), that up to 1000 ppm of uranyl ions can quantitatively be removed (>97 %) in a single CPE extraction using optimum conditions.

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Summary

Experimental conditions of cloud-point extraction (CPE) for the selected five acidic and neutral medicaments (salicylic acid, opipramol, carbamazepine, lorazepam, and alprazolam) in human plasma were studied and optimized. Separation and detection of the tested drugs were performed by the high-performance liquid chromatography with diode array detection (HPLC-DAD) method in an appropriate gradient mode using a column Nucleosil C8. Under the optimized conditions, main validation parameters were determined for all the compounds. The extraction yields (%) ranged from 54.12 to 82.17 with intra- and interday repeatability (RSD, %) 5.70–9.92 and 5.79–10.19, respectively. The detection limit was 0.5 μg mL−1 for all the tested drugs with exception of salicylic acid (LOD = 2.5 μg mL−1). The linearity of the proposed method was examined for the four drugs: opipramol, carbamazepine, lorazepam, and alprazolam in the concentration range of 0.5–2.0 μg mL−1 (correlation coefficient r 2 = 0.995–0.999) and for salicylic acid in the concentration range of 2.5–10.0 μg mL−1 (correlation coefficient r 2 = 0.993). The analytical parameters for the medicaments tested in whole blood were unsatisfactory, especially in terms of extraction recovery and repeatability, and application of the developed procedure for this biological matrix requires further study.

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