Cloud Point Extraction System Research Articles

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

Abstract 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.

Successive preconcentration and mechanistic investigation of Au(iii), Pd(ii), Pt(iv) and Rh(iii) via cloud point extraction using a functionalised ionic liquid

This study proposes the efficient separation of Au(iii)/Pd(ii)/Pt(iv)/Rh(iii) through the 2-mercaptobenzothiazole-functionalised ionic liquid ([C6mim][2MBT]) using a cloud point extraction system.

Determination of polonium-210 in environmental samples using diglycolamide-based cloud point extraction coupled to alpha spectrometry analysis

This study presents a novel cloud point extraction (CPE) methodology for the separation and enrichment of polonium-210 prior to alpha-spectrometric quantification in water, urine and digested samples. The extractive behaviour of diglycolamide-based ligands towards Po by CPE was determined and optimised in various acidic conditions. The extraction efficiency and selectivity of the CPE systems depend greatly on the choice of the extracting agent and acidic conditions. The thorough optimisation of those specific parameters has led to the development of a suitable cloud point extraction system for the determination of polonium-210 at ultra-trace levels compatible with alpha-spectrometry. To facilitate this coupling, a back-extraction procedure was optimised and performed on the surfactant-rich phase to enable the spontaneous deposition of polonium-210 onto a silver disk; this also avoids making the matrix transfer step mandatory due to the presence of a nitric medium. Method detection and quantification limits of 3.5 and 12 mBq L−1, respectively, were determined by alpha spectrometry. The robustness of the proposed methodology was demonstrated by the determination of polonium ions concentration in various environmental and biological samples and solid certified reference materials.

Міцелярна екстракція катіонних ПАР та їх іонних асоціатів з додецилсульфат-аніоном фазами неіонної ПАР при температурі помутніння

The distribution of individual cationic surfactants and their ionic associates with the anionic surfactant in the cloud point extraction systems, based on non-ionic surfactant OP-7 was investigated. Determined that the dependence of the extraction degree of halides alkylpyridiniums on carboxylic change length in optimal conditions for extraction is characterized by the existence of maximum for cationic surfactant where n = 12. Decrease as well as increase in carboxylic change length of cation of alkylpyridiniums diminishes the effectiveness of their extraction into the surfactant-rich phase. The peculiarities of inter phase distribution of ionic associates cationic surfactant – anionic surfactant in the micellar extraction systems are investigated. It was shown, that with the increase in carboxylic change length of cationic surfactant the dependence of extraction degree of associates with anionic surfactant is characterized by the existence of the maximum. Most effective into the surfactant-rich phase extracted of ionic associates of three- and tetradecylpyridinium. Decreasing and increasing of hydrophobicity of alkylpyridiniums diminishes the effectiveness of extraction of associates. The established effects are explained by the hydrophobic correspondence between the substrate and the surfactant-rich phase of non-ionic surfactant.

Determination of solubilization isotherm in micelles of non-ionic surfactant L62 for butanol extraction

Earlier studies with extractive butanol fermentation using non-ionic surfactant L62 showed significant increase in butanol titer by 50–125%. Butanol was further separated from fermentation broth using L62 in a cloud point extraction system. The present work was undertaken to determine the solubilization of butanol in L62-water system. Experiments were conducted to study the effect of different parameters on butanol extraction efficiency. Optimum conditions i.e. 3% L62 (v/v) with 4% (v/v) butanol concentration at 45 °C for 30 min resulted into extraction efficiency of 40.8% (w/w). The Langmuir isotherm was fitted and isotherm parameters were found to be m = 129.87 (mol/mol) and n = 0.308 (L/mol). Langmuir isotherm with estimated parameters was used to predict the surfactant concentration to extract butanol with desired efficiency. Predicted and experimental results were in close agreement (96% accuracy). Thus, Langmuir model can be successfully used to design the cloud point extractor and predict the extraction efficiency/surfactant concentration for L62-butanol-water system with great accuracy.

The peculiarities of the interphase distribution of amino acids in the cloud point extraction systems

This study presents the particularities of interphase distribution of amino acids between water and non-ionic surfactant-rich phase at cloud point temperature. The influence of a number of hydrophobic/structural parameters of amino acids, such as total hydrophobicity (logP), hydropathy index (Hi), which characterized the nature of amino acid fragment, total molecular surface of amino acids (Sa), their polarity (F), electronegativity of the molecule (X), the maximum possible number of hydrogen bonds, which may form a molecule (Hb), the molecular refraction (Mr), the value of organic (O) and the value of inorganic (I) properties on effectiveness of their cloud point extraction have been studied. Based on obtained data, the equation logD=1.05–0.005Mr+0.004Sa–0.030Hb–0.008F has been suggested to describe the interphase transfer of amino acids into surfactant-rich phase. The values of solvation free Gibbs energy for the interphase transfer of amino acids into the surfactant-rich phase were also calculated. The obtained values of free Gibbs energy of amino acids in cloud point extraction system were in the range from −4.4 to −8.0kJmol−1. A significant difference between thermodynamic parameters of the cloud point extraction and traditional liquid-liquid extraction with organic solvents is reflected in the ability of surfactant-rich phase extract both hydrophobic and hydrophilic compounds as a consequence of “high organization” and supramolecular nature of this type of phase.

Recovery of Ru(III) from hydrochloric acid by cloud point extraction with 2-Mercaptobenzothiazole-functionalized ionic liquid

An arisen and environment-friendly method of cloud point extraction (CPE) which involved Octylphenoxypolyethoxyethanol (TX-114) as surfactant and 2-Mercaptobenzothiazole-functionalized ionic liquid as extractant was carried out to separate Ru(III) from aqueous phase to bottom surfactant phase for the first time. A host of variable (e.g., the extractant concentration, hydrochloric acid concentration, nitric acid concentration, TX-114 mass fraction, TX-114 volume and sodium chloride concentration) were evaluated and optimized to investigate the extraction behavior. At optimized experimental conditions, the extraction percentage of Ru(III) was found to be 82%, together with the enrichment factor of 40. A special complexation extraction mechanism of Ru(III) in CPE process was studied systemically and confirmed via job method, UV–vis spectrum and FT-IR spectrum in detail. Taking together, the rational-designed functional ionic liquid as a novel extractant exhibited superior extractability for Ru(III) in CPE system.

Development of a method for the determination of cadmium levels in seawater by flame atomic absorption spectrometry using an online cloud-point extraction system

A new system was developed for the preconcentration and determination of cadmium levels in water following online cloud-point extraction and analysis by flame atomic absorption spectrometry. The method uses cloud-point extraction of the complex formed between Cd(II) ions and the reagent 2-(5-bromo-2'-thiazolylazo)-$p$-cresol (Br-TAC) using Triton X-114 as a surfactant. The main steps of the procedure, extraction, filtration, and detection were conducted online. Parameters that influence the experimental conditions of online preconcentration systems were examined, including pH, concentration of reagent and surfactant, and flow of sample and eluent. The limit of detection of the method is 0.2 $\mu $g L$^{-1}$. The preconcentration system exhibits an enrichment factor of 19, an analytical frequency of 60 h$^{-1}$, and a consumptive index of 0.12 mL. The procedure was applied to the determination of cadmium levels in seawater samples.

Cloud point extraction of 2,4−dichlorophenol from aqueous samples employing β−cyclodextrin

ABSTRACTIn this study, β−cyclodextrin (β−CD) was used to enhance the extraction of 2,4−dichlorophenol (2,4−DCP) from the aqueous sample in cloud point extraction (CPE) using spectrophotometric method. Several parameters have been investigated with and without the presence of β−CD modifier, such as pH, equilibration temperature, analyte concentration, and water content in the CPE and CPE−βCD systems, respectively. Equilibrium data are described by the Langmuir isotherm in both CPE systems with and without β−CD modifier. The thermodynamic parameters (positive values of ΔH° and ΔS°, negative values of ΔG°) indicate that the solubilization of 2,4−DCP in a polyethylene glycol silicone surfactant (DC193C) is endothermic, entropy gained, and spontaneous in both systems. In the CPE−βCD system, the results show that the β−CD modifier is capable of enhancing the extraction of 2,4−DCP pollutant from aqueous samples.

Extraction of p-coumaric acid and ferulic acid using surfactant-based aqueous two-phase system.

Ferulic acid (FA) and p-coumaric acid (pCA) are high-value products that can be obtained by alkaline hydrolysis of lignocellulose. Present work explores the potential of surfactant-based cloud-point extraction (CPE) for FA and pCA extraction from corn cob hydrolysate. More than 90 % (w/w) extraction of both FA and pCA was achieved from model system with L92. The partition coefficient of FA and pCA in L92 aqueous phase system was 35 and 55, respectively. A significant enrichment (8-10-fold) of both FA and pCA was achieved in surfactant-rich phase. Furthermore, the downstream process volume was reduced by 10 to 13 times. Optimized conditions (5 % v/v L92 and pH 3.0) resulted into 85 and 89 % extraction of FA and p-CA, respectively, from alkaline corn cob hydrolysate. Biocompatibility tests were carried out for L92 for ethanol fermentation and found to be biocompatible. Thus, the new surfactant-based CPE system not only concentrated FA and pCA but also reduced the process volume significantly. Further, aqueous phase containing sugars can be used for ethanol fermentation.

Detoxification of corn stover hydrolysate using surfactant‐based aqueous two phase system

AbstractBACKGROUNDPretreatment methods used to break down lignocellulose structure lead to the generation of compounds that inhibit ethanol fermentation. Hence, removal of these compounds is essential for improved fermentability. The surfactant‐based cloud point extraction (CPE) aqueous two phase system is a new method having the potential for separation and recovery of inhibitors. The present work examines the potential of surfactants‐based CPE systems as a detoxification method.RESULTSSurfactants L62D and L62LF achieved more than 90% removal of phenolic compounds and less than 20% removal of acetic acid and HMF from a model system when the surfactant concentration was 1% and 5%. With untreated simulated hydrolysate containing inhibitors the fermentation was inhibited completely. Detoxification of the same hydrolysate with L62D (1% and 5%) and L62LF (1% and 5%) showed complete fermentation with high ethanol productivity (0.61 g L‐1 h‐1). Similarly, the detoxified corn stover hydrolysate showed delayed fermentation. The productivity increased by 30% after detoxification with 1% of the two surfactants and by 100% with 5% of the surfactants (L62D and L62LF).CONCLUSIONThe new surfactant‐based detoxification method significantly improved the fermentability of simulated hydrolysate and corn stover hydrolysate. © 2013 Society of Chemical Industry

Microchip-based Cloud Point Extraction System and Its Application to Determination of p -Nitrophenol in Water Samples

A method was developed by integrating cloud point extraction into a microchip.Complicated operations in conventional cloud point extraction process,such as mixing,heating,and centrifugation,were avoided.The system was composed of two poly( methyl methacrylate)( PMMA) plates with the microchannels sandwiched in between.The collection material was integrated in the microchip to entrap the surfactant phase,and then the entrapped surfactant phase was eluated for sequent UV-Vis spectrophotometric determinations.The analytical performances of the microchip-based cloud point extraction system were evaluated with p-nitrophenol as a model test analyte.Effects of various parameters were optimized.The optimal conditions were as follows: sample flow rate of 0.15 mL/min,sample volume of 0.5 mL,sample pH of 11.0,surfactant concentration of 1.5%,methanol-water with a volume ratio of 70 ∶ 30 as the eluent,eluent flow rate of0.14 mL/min,and eluent volume of 0.7 mL.Within the linear range of 0.25-12 mg/L,the limit of detection was determined as 0.075 mg/L.The intra-day and inter-day relative standard deviations were 2.8%and 6.4%,respectively.When applied to the determination of p-nitrophenol in environmental water samples,the recovery values were in the range of 90.8%-102.7%.

Cloud point extraction of 99Mo with Triton X-114

This paper reports the cloud point extraction (CPE) extraction behaviour of 99Mo in non-ionic Triton X-114 (TX-114), sodiumdodecyl sulphate (SDS) + TX-114 and sodium diethyldithiocarbamate (DDTC) + TX-114. The high extraction of 99Mo observed in all the CPE systems in pH 5 or less. The extent of extraction was almost unchanged with addition of SDS and DDTC in TX-114. Extraction behaviour was also studied in presence of common salts. It was observed the presence of salts dramatically decreased the amount of molybdenum extraction in the surfactant-rich phase.

Cloud point and solvent extraction study of uranium(VI) by 8-hydroxyquinoline

BACKGROUND: Cloud point extraction (CPE) is an attractive alternative to solvent extraction. However, comparisons between both techniques are lacking. In this paper, the extraction of uranium(VI) using 8-hydroxyquinoline (HQ) as chelating agent was studied by CPE using Triton X-114 as non-ionic surfactant and by solvent extraction using CHCl3 as diluent. RESULTS: Using CPE, a quantitative extraction was observed for pH higher than 4.5 with a HQ/U ratio of 10. Using solvent extraction an increase in the HQ/U ratio up to 50 is necessary to obtain a near quantitative extraction. Both extraction systems were then compared with respect to the nature of extracted species, and the extraction constants determined using log-log analysis of the extraction data. In the solvent extraction system, the extracted species were identified as UO2Q2 and the corresponding extraction constant was found to be log kex = − 3.6 ± 0.2 on the molar scale. Considering that UO2Q2 is also the extracted species in CPE, a slightly higher extraction constant, i.e. log kex = − 2.5 ± 0.3, was found. CONCLUSION: Such a small difference in favour of the CPE system may arise from the combination of various phenomena, including effects of temperature and effects of ‘extractant environment’. However, a change in the nature of the extracted species, namely from UO2Q2 in the solvent extraction system to the formation of adducts, i.e. UO2Q2(HQ) and UO2Q2(HQ)2 in the CPE system, due to higher HQ concentration in the surfactant-rich phase compared with chloroform, cannot be precluded, but requires confirmation. Copyright © 2012 Society of Chemical Industry

Study on the Cloud Point Extraction of Gd(III) with 8-Hydroxyquinoline

The extraction of gadolinium was studied using Cloud Point Extraction (CPE) with 8-hydroxyquinoline (8-HQ) as a chelating agent. The structure of the extracted Gd3+ complex with 8-HQ in the micelle of Triton X114 was determined using log-log analysis of the extraction data. A ratio of 8-HQ to Gd3+ of 3:1 was found. The CPE results were compared with those obtained by classical liquid-liquid extraction with chloroform as solvent. The parameters of the extraction process in both media were determined and compared. A quantitative extraction of Gd3+ at pH 5.5 was obtained by CPE using a 8-HQ/Gd3+ ratio of 10 although a 8-HQ/Gd3+ ratio of 500 was necessary for solvent extraction using chloroform as solvent, illustrating an increase of the mass action of extractants when using CPE instead of solvent extraction. Under those conditions, a higher extraction constant was determined for CPE compared with solvent extraction even if the formation of adducts in the CPE system could not be checked experimentally.

Use of Cloud Point Extraction with Derivatizing Reagent for the Extraction and Determination of Isoniazid

A simple and sensitive cloud point extraction high-performance liquid chromatography method is proposed for the determination of isoniazid in blood. The procedure is based on the product of the reaction of isoniazid with benzaldehyde. It can be validated that there is a linear relationship between the signal of isonicotinyl hydrazone and the concentration of isoniazid. A cloud point extraction system of nonionic surfactant Triton X-100 is applied for preconcentration of isonicotinyl hydrazone. Then the analytes in surfactant-rich phase are detected with HPLC-UV system. calibration graph was obtained in the range of 2.0 × 10(-3)-0.5 mg/L, the detection limit was 5.0 × 10(-4) mg/L. Method validation is performed on serum samples spiked at two levels, the recoveries ranging from 82.17-83.81%, with relative standard deviations from 2.45% to 3.89%.

Development of Cloud Point Extraction for Simultaneous Extraction and Determination of Platinum and Palladium Using Inductively Coupled Plasma Optical Emission Spectrometry in Platinum-Palladium Spent Catalysts

A new on-line cloud point extraction system coupled to inductively coupled plasma optical emission spectrometry was designed for simultaneous extraction, preconcentration and determination of trace amounts of platinum and palladium in platinum-palladium spent catalysts. This was based on the complexation of the metal ions with 1,8-diamino-4,5-bis(hydroxyamino)anthraquinone reagent in the presence of non-ionic surfactant of Triton X-114. After phase separation, the surfactant-rich phase was diluted with concentrated HNO3 (70%, w/w); the analytes concentrations were determined by inductively coupled plasma-optical emission spectrometry. Several factors influencing the instrumental conditions and extraction were evaluated and optimized. Under the optimum conditions, the enhancement factors of the proposed method were 35.4 and 29 for platinum and palladium, respectively. The detection limits were 0.3 and 0.45 µ g L−1. Finally, the developed method was successfully applied to the extraction and determination of platinum and palladium in platinum-palladium spent catalysts samples and satisfactory results were obtained.

Cloud Point Extraction of Bisphenol A from Water Utilizing Cationic Surfactant Aliquat 336

Abstract In this study, cloud-point extraction (CPE) using a cationic surfactant, tricaprylmethylammonium chloride (Aliquat 336), was carried out to separate and concentrate bisphenol-A (BPA) from aqueous media. Cloud-point phase separation of Aliquat 336 at room temperature (25 °C) was induced by the addition of Na2SO4. The parameters influencing the extraction efficiency, such as concentrations of Aliquat 336 and Na2SO4, cosolvent (methanol), pH value and extraction time were evaluated. The results showed that the extraction efficiency was practically constant in the studied range of Aliquat 336, cosolvent (methanol), pH, and dissolved organic matters. Under the operational CPE conditions, distribution constant, KD, of the distribution of BPA between the surfactant-rich and aqueous phases of the CPE system was estimated to be approximately 104. Coupled to liquid chromatography with UV detection, the CPE method offered a detection limit of 0.34 μg l−1 in distilled water and recovery of BPA ranged from 90% to 108.6% with a sample volume of 50 ml in the three matrices studied. The high extraction efficiency might be due to the combination of ion pair, hydrophobic effects, and cation-π interaction, based on the micellars' size distribution and Zeta potential analysis.

An on-line cloud point extraction system for flame atomic absorption spectrometric determination of trace manganese in food samples

The development of an on-line preconcentration system with cloud point extraction for the determination of manganese is described. The system was used to determine manganese levels in food samples using flame atomic absorption spectrometry (FAAS). All steps of the cloud point extraction procedure were performed on-line, from the mixing of reagents to detection. The manganese ions are complexed in a mixture of the reagent 2-[2′-(6-methyl-benzothiazolylazo)]-4-bromophenol (Me-BTABr) and Triton X-114. The components are retained on a minicolumn and then desorbed with eluent acid to subsequent detection of manganese by FAAS. Under the optimized conditions, the method presented a detection limit of 0.7 μg L − 1 and an enrichment factor of 17 to a volume of 3000 μL. The sampling frequency was 30 h − 1 . The accuracy of the method was tested by evaluating the amount of Mn in certified reference materials (apple leaves NIST 1515 and spinach leaves NIST 1570a). The proposed procedure was applied to food samples (shrimp powder, flaxseed flour, wheat flour, soy flour and oat), and the results agreed with those obtained by the determination of Mn in foods by atomic absorption spectrometry with electrothermal atomization (ETAAS).

Development of a new sequential injection in-line cloud point extraction system for flame atomic absorption spectrometric determination of manganese in food samples

A preconcentration method for manganese determination by sequential injection cloud point extraction with subsequent detection by flame atomic absorption spectrometry (FAAS) has been developed. The enrichment of Mn was performed after a preliminary on-line cloud point extraction and entrapment of manganese-containing surfactant aggregated within a minicolumn packed with cotton. The laboratory-made reagent 4-(5′-bromo-2′-thiazolylazo)orcinol (Br-TAO) and the surfactant Triton X-114 were used for cloud point extraction. The manganese ions were eluted with sulphuric acid solution and directly introduced into the FAAS. Chemical and flow variables affecting the preconcentration were studied. Using a sample volume of 2.80 mL the limit of detection and enrichment factor were calculated to be 0.5 μg L −1 and 14, respectively. The sample frequency is 48 h −1, considering a total run cycle of 75 s. The accuracy of the proposed method has been demonstrated by the analysis of the certified reference biological materials rice flour and tomato leaves. The method has been applied to determination of manganese in food samples.