Cloud Point Extraction Method Research Articles

Cloud point extraction-flame atomic absorption spectrometry for pre-concentration and determination of trace amounts of silver ions in water samples.

A cloud point extraction (CPE) method was used as a pre-concentration strategy prior to the determination of trace levels of silver in water by flame atomic absorption spectrometry (FAAS) The pre-concentration is based on the clouding phenomena of non-ionic surfactant, triton X-114, with Ag (I)/diethyldithiocarbamate (DDTC) complexes in which the latter is soluble in a micellar phase composed by the former. When the temperature increases above its cloud point, the Ag (I)/DDTC complexes are extracted into the surfactant-rich phase. The factors affecting the extraction efficiency including pH of the aqueous solution, concentration of the DDTC, amount of the surfactant, incubation temperature and time were investigated and optimized. Under the optimal experimental conditions, no interference was observed for the determination of 100 ng·mL−1 Ag+ in the presence of various cations below their maximum concentrations allowed in this method, for instance, 50 μg·mL−1 for both Zn2+ and Cu2+, 80 μg·mL−1 for Pb2+, 1000 μg·mL−1 for Mn2+, and 100 μg·mL−1 for both Cd2+ and Ni2+. The calibration curve was linear in the range of 1–500 ng·mL−1 with a limit of detection (LOD) at 0.3 ng·mL−1. The developed method was successfully applied for the determination of trace levels of silver in water samples such as river water and tap water.

Extraction, preconcentration and spectrophotometric determination of trace levels of thiosulfate in environmental waters

In the existing study, a new vortex-assisted cloud point extraction (VA-CPE) method was developed for determination of low levels of thiosulfate in environmental waters at 632 nm by spectrophotometry. The method is selectively based on charge-transfer-sensitive ion-pair complex formation of Ag(S2O3)23−, which is produced by the reaction of thiosulfate with excess Ag+ ions with toluidine blue (3-amino-7-dimethylamino-2-methylphenazathionium chloride, TB+) and then its extraction into micellar phase of polyethylene glycol 4-tert-octylphenyl ether (Triton X-45) in presence of Na2SO4 as salting-out agent at pH 7.0. All the factors affecting complex formation and VA-CPE efficiency were optimized in detail. Under the optimized conditions, the linear calibration curves for thiosulfate were in the range of 0.2–120 and 5–180 µg L−1 with sensitivity improvement of 81-folds and 15-folds, respectively, as a result of efficient mass transfer obtained by CPE with and without vortex, while it changed in the range of 260–3600 µg L−1 without preconcentration at 642 nm. The limits of detection and quantification of the method for VA-CPE were found to be 0.05 and 0.22 µg L−1, respectively. The precision (expressed as the percent relative standard deviation) was in range of 2.5–4.8% (5, 10 and 25 µg L−1, n: 5). The method accuracy was validated by comparing the results to those of an independent 5,5′-dithiobis(2-aminobenzoic acid) (DTNB) method as well as recovery studies from spiked samples. It has been observed that the results are statistically in a good agreement with those obtained by DTNB method. Finally, the method developed was successfully applied to the preconcentration and determination of trace thiosulfate from environmental waters.

Separation and quantification of metallic nanoparticles using cloud point extraction and spectrometric methods: a brief review of latest applications

Reliable quantification of metallic nanoparticles in complex matrices is a difficult task.

Preconcentration and determination of titanium in tap water, geological and sunscreen cream samples by CPE-FAAS method

In the presented research, a cloud-point extraction method has been used for the preconcentration of trace amounts of Ti(IV) after complex formation with cupferron (phenyl-nitroso-hydroxylamine ammonium) using Triton X-114 as the surfactant. The chemical variables affecting the phase separation and the signal of flame atomic absorption spectrometry were optimized. At pH = 3.0, preconcentration of the analyte content sample in the presence of 0.07% (w/v) Triton X-114 and 8.6 × 10−5 M cupferron enabled the detection limit (3Sb/m) of 0.01 µg/mL Ti(IV) and linear range 0.03–3.00 µg/mL to be achieved. The enhancement factor and preconcentration factor were 37 and 30 respectively. The relative standard deviation by repeated assays of six separate solution of 0.67 µg/mL Ti(IV) was also obtained 3.9%. The proposed method was applied to the determination of Ti(IV) in tap water, sand, feldspar, and sunscreen cream.

Cloud point extraction and diffuse reflectance-Fourier transform infrared spectroscopic determination of chromium(VI): A probe to adulteration in food stuffs.

A new cloud point extraction (CPE) method for the determination of hexavalent chromium i.e. Cr(VI) in food samples is established with subsequent diffuse reflectance-Fourier transform infrared (DRS-FTIR) analysis. The method demonstrates enrichment of Cr(VI) after its complexation with 1,5-diphenylcarbazide. The reddish-violet complex formed showed λmax at 540nm. Micellar phase separation at cloud point temperature of non-ionic surfactant, Triton X-100 occurred and complex was entrapped in surfactant and analyzed using DRS-FTIR. Under optimized conditions, the limit of detection (LOD) and quantification (LOQ) were 1.22 and 4.02μgmL-1, respectively. Excellent linearity with correlation coefficient value of 0.94 was found for the concentration range of 1-100μgmL-1. At 10μgmL-1 the standard deviation for 7 replicate measurements was found to be 0.11μgmL-1. The method was successfully applied to commercially marketed food stuffs, and good recoveries (81-112%) were obtained by spiking the real samples.

Cloud point extraction method for bio-accessible arsenic determination in corn and rice samples

Cloud point extraction method for bio-accessible arsenic determination in corn and rice samples

Cloud point extraction of methylphenol in water samples with low viscosity of non-ionic surfactant Sylgard 309 coupled with high-performance liquid chromatography

ABSTRACTA cloud point extraction method is developed for the extraction of methylphenol from various water samples using the non-ionic surfactant, Sylgard-309. Methylphenol in the water is a toxic element that is dangerous to humans. Hence, the treatment of water containing methylphenol is necessary. The method’s optimum conditions are 2.0 M salt concentration and 10% of surfactant concentration at room temperature. The limit of detection and limit of quantification of the method is 0.109 ppm and 0.365, respectively. The extraction recoveries of methylphenol in water samples (tap water, lake water, river water and sea water) are in the range of 90–99% with the relative standard deviations of less than 1.5%.

Solvo-Surfactant Properties of Dialkyl Glycerol Ethers: Application as Eco-Friendly Extractants of Plant Material through a Novel Hydrotropic Cloud Point Extraction (HCPE) Process

Six dialkyl glycerol ethers with short alkyl chains have been synthesized, and their solvo-surfactant properties have been compared to those of the mono- and trisubstituted isomers. The dialkyl ethers are completely miscible with water at room temperature, and some of them show a cloud point. In aqueous solution, they are much better solubilizers of Disperse Red 13 hydrophobic dye than the trialkyl ethers. They also have much lower boiling points than the isomeric monosubstituted counterparts. These features make the dialkyl glycerol ethers attractive for aqueous extraction of hydrophobic material. Their volatility allows an easier recovery of solute compared to when nonvolatile nonionic surfactants are used, as in the standard cloud point extraction (CPE) process. The effectiveness of the novel hydrotropic cloud point extraction (HCPE) method proposed in this work is illustrated by extraction of piperine from black pepper using an aqueous solution of 1-butyl-3-methyl glycerol ether that is an attractive ...

Application of conventional and modified cloud point extraction for simultaneous enrichment of cadmium, lead and copper in lake water and fish muscles

A new method based on modification of cloud point extraction for simultaneous enrichment of cadmium, lead and copper in water and fish muscle samples was proposed. The extraction efficiency by modified cloud point extraction (m-CPE) was compared with conventional cloud point extraction (c-CPE) method. The procedure for both CPE methods was comprised of formation of metal complexes with a hydrophobic chelating agent, dithizone, followed by entrapment of the chelates in a nonionic surfactant, Triton X-114. For c-CPE, the surfactant rich phase was treated with ethanolic solution of nitric acid and analyzed by flame atomic absorption spectrometer (FAAS). Whereas for m-CPE, aqueous nitric acid was used to back extract the metal ions from the surfactant rich phase and finally determined. The efficiency of the methods was tested by analyzing certified reference material and standard addition to a real sample. All the experimental parameters were optimized. At optimized experimental conditions, preconcentration and enhancement factors were 62.5 and 78.0 to 83.0 respectively for m-CPE, 25.0 and 56.0% higher than that of c-CPE. This improvement might be due to elimination of the effects of surfactant on the signal of analytes by FAAS. The developed method of m-CPE was applied successfully for analysis of the selected heavy metals in water and muscle tissues samples of fish of different lakes in Sindh, Pakistan.

Cloud-point extraction is compatible with liquid chromatography coupled to electrospray ionization mass spectrometry for the determination of antazoline in human plasma

Cloud-point extraction (CPE) is attracting increasing interest in a number of analytical fields, including bioanalysis, as it provides a simple, safe and environmentally-friendly sample preparation technique. However, there are only few reports on the application of this extraction technique in liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI–MS/MS) analysis. In this study, CPE was used for the isolation of antazoline from human plasma. To date, only one method of antazoline isolation from plasma exists—liquid–liquid extraction (LLE). The aim of this study was to prove the compatibility of CPE and LC-ESI–MS/MS and the applicability of CPE to the determination of antazoline in spiked human plasma and clinical samples.Antazoline was isolated from human plasma using Triton X-114 as a surfactant. Xylometazoline was used as an internal standard. NaOH concentration, temperature and Triton X-114 concentration were optimized. The absolute matrix effect was carefully investigated. All validation experiments met international acceptance criteria and no significant relative matrix effect was observed. The compatibility of CPE and LC-ESI–MS/MS was confirmed using clinical plasma samples. The determination of antazoline concentration in human plasma in the range 10–2500ngmL−1 by the CPE method led to results which are equivalent to those obtained by the widely used liquid-liquid extraction method.

Application of ultrasonic-assisted cloud point extraction/flame atomic absorption spectrometry (UA-CPE/FAAS) for preconcentration and determination of low levels of antimony in some beverage samples

Due to be able to migrate or leach from food packaging materials into the foods and/or beverages, development of a new, sensitive and selective analytical methods for low levels of antimony as a food contaminant is of great importance in terms of food safety. In this context, an ultrasonic-assisted cloud point extraction method was developed for the preconcentration and determination of antimony as Sb(III) using 4-(2-thiazolylazo)resorcinol (TAR) and 2-(2-thiazolylazo)-p-cresol (TAC) as chelating agents and sodium dodecyl sulfate as signal enhancing agent at pH 6.0 and mediated by nonionic surfactant, t-octylphenoxypolyethoxyethanol by flame atomic absorption spectrometry. Using the optimized conditions, the calibration curves obtained from Sb(III) with TAR and TAC were linear in the concentration ranges of 0.5–180 and 1–180 μg L−1 with detection limits of 0.13 and 0.28 μg L−1, respectively. The precision (as relative standard deviations, RSDs) was lower than 3.9 % (25 and 100 μg L−1, n: 6). The method accuracy was validated by the analysis of two standard reference materials. The results obtained were statistically in a good agreement with the certified values at 95 % confidence limit. The method has successfully been applied to the determination of Sb(III) and total Sb in selected beverages, milk and fruit-flavored milk products before and after pre-reduction of Sb(V) to Sb(III) with a mixture of KI/ascorbic acid in acidic media. The Sb(V) contents of samples were quantitatively calculated from analytical difference between total Sb and Sb(III) levels.

A New Ultrasound Assisted-Cloud Point Extraction Method for the Determination of Trace Levels of Tin and Antimony in Food and Beverages by Flame Atomic Absorption Spectrometry

In the current study, a new ultrasonic-assisted cloud-point extraction (UA-CPE) method for the preconcentration and determination of antimony and tin in the selected food and beverages was developed by flame atomic absorption spectrometry (FAAS). The method is based on the fact that formation of the stable ternary complexes of Sb(III) and Sn(IV) with 2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one (morin) in presence of cetyltrimethylammoniumbromide (CTAB) as both sensitivity improvement auxiliary ligand and counter ion, and then extraction into the micellar phase of poly(ethylene glycol-mono-p-nonylphenylether (PONPE 7.5) as extracting agent at pH 8.5. Under the optimized conditions, the calibration curves for Sb(III) and Sn(IV) were rectilinear with changing calibration sensitivities in ranges of 0.1–140 and 0.1–225 μg L−1, respectively. The limit of detection for both Sb(III) and Sn(IV) was 0.03 μg L−1 with sensitivity enhancement factor of 114.5 and 110.6, respectively. The precision as a relative standard deviation (RSD) for Sb(III) and Sn(IV) is in range of 2.3–5.2 and 2.6–5.4 %, respectively. The trueness of the method was verified by analysis of certified reference materials (CRMs). The method was successfully applied to determination of antimony and tin in the selected food and beverage matrices.

Determination of thorium(IV) in real samples by spectrophotometry after micelle-mediated cloud point extraction

A simple and sensitive cloud point extraction method for the preconcentration of thorium(IV) prior to spectrophotometric determination was developed. The method was based on the formation of complex of thorium(IV) with quinalizarin at pH 5.0 and mixed micelle-mediated extraction of the complex using cethyltrimethyl ammonium bromide and Triton X-114. The enriched analyte in the surfactant-rich phase was determined spectrophotometrically at 600 nm. The effect of optimal extraction and reaction conditions was studied. Under the optimum conditions, linearity was obeyed over the range of 5.0–100 ng mL−1 and the limit of detection was 1.40 ng mL−1. The proposed method was validated and successfully applied for the determination of thorium(IV) in certified reference materials and real samples with satisfactory results.

An evaluation of the bioaccessibility of arsenic in corn and rice samples based on cloud point extraction and hydride generation coupled to atomic fluorescence spectrometry

A simple, inexpensive and rapid method was proposed for the determination of bioaccessible arsenic in corn and rice samples using an in vitro bioaccessibility assay. The method was based on the preconcentration of arsenic by cloud point extraction (CPE) using o,o-diethyldithiophosphate (DDTP) complex, which was generated from an in vitro extract using polyethylene glycol tert-octylphenyl ether (Triton X-114) as a surfactant prior to its detection by atomic fluorescence spectrometry with a hydride generation system (HG-AFS). The CPE method was optimized by a multivariate approach (two-level full factorial and Doehlert designs). A photo-oxidation step of the organic species prior to HG-AFS detection was included for the accurate quantification of the total As. The limit of detection was 1.34μgkg−1 and 1.90μgkg−1 for rice and corn samples, respectively. The accuracy of the method was confirmed by analyzing certified reference material ERM BC-211 (rice powder). The corn and rice samples that were analyzed showed a high bioaccessible arsenic content (72–88% and 54–96%, respectively), indicating a potential human health risk.

Biosorptive removal of inorganic arsenic species and fluoride from aqueous medium by the stem of Tecomella undulate

Simultaneous removal of fluoride (F−), inorganic arsenic species, AsIII and AsV, from aqueous samples has been performed using an economic indigenous biosorbent (Stem of Tecomella undulata). The inorganic As species in water samples before and after biosorption were determined by cloud point and solid phase extraction methods, while F− was determined by ion chromatography. Batch experiments were carried out to evaluate the equilibrium adsorption isotherm studies for AsIII, AsV and F− in aqueous solutions. Several parameters of biosorption were optimized such as pH, biomass dosage, analytes concentration, time and temperature. The surface of biosorbent was characterized by SEM and FTIR. The FTIR study indicated the presence of carbonyl and amine functional groups which may have important role in the sorption/removal of these ions. Thermodynamic and kinetic study indicated that the biosorption of AsIII, AsV and F− were spontaneous, exothermic and followed by pseudo-second-order. Meanwhile, the interference study revealed that there was no significant effect of co-existing ions for the removal of inorganic As species and F− from aqueous samples (p > 0.05). It was observed that the indigenous biosorbent material simultaneously adsorbed AsIII (108 μg g−1), AsV (159 μg g−1) and F− (6.16 mg g−1) from water at optimized conditions. The proposed biosorbent was effectively regenerated and efficiently used for several experiments, to remove the AsIII, AsV and F− from real water sample collected from endemic area of Pakistan.

Isotopic signature of selected lanthanides for nuclear activities profiling using cloud point extraction and ICP-MS/MS

The presence of fission products, which include numerous isotopes of lanthanides, can impact the isotopic ratios of these elements in the environment. A cloud point extraction (CPE) method was used as a preconcentration/separation strategy prior to measurement of isotopic ratios of three lanthanides (Nd, Sm, and Eu) by inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). To minimise polyatomic interference, the combination of interferents removal by CPE, reaction/collision cell conditions in He and NH3 mode and tandem quadrupole configuration was investigated and provided optimal results for the determination of isotopic ratio in environmental samples. Isotopic ratios were initially measured in San Joaquin soil (NIST-2709a), an area with little contamination of nuclear origin. Finally, samples collected from three sites with known nuclear activities (Fangataufa Lagoon in French Polynesia, Chernobyl and the Ottawa River near Chalk River Laboratory) were analysed and all exhibited altered isotopic ratios for 143/145Nd, 147/149Sm, and 151/153Eu. These results demonstrate the potential of CPE and ICP-MS/MS for the detection of altered isotopic ratio in environmental samples collected in area subjected to nuclear anthropogenic contamination. The detection of variations in these isotopic ratios of fission products represents the first application of CPE in nuclear forensic investigations of environmental samples.

Application of CPE-FAAS Methodology for the Analysis of Trace Heavy Metals in Real Samples using Phenanthraquinone Monophenyl Thiosemicarbazone and Triton X-114

In the present study, a cloud point extraction method was used for the preconcentration and extraction of cadmium (II) and zinc (II) ions in different environmental samples. The zinc and cadmium ions formed hydrophobic complexes with phenanthraquinone monophenyl thiosemicarbazone (PPT). These complexes were extracted using Triton X-114 nonionic surfactant. The surfactant-rich phase was diluted with acidified methanol. Then, the concentrations of the metal ions were determined by FAAS. The experimental factors controlling the process of separation are investigated e.g., pH, complexing agent concentration, surfactant's concentration, temperature, and incubation time. The present CPE-FAAS procedure has been used to preconcentrate and determine Cd(II) and Zn(II) metal ions in natural water samples, drug samples and certified reference materials. The LODs for cadmium(II) and zinc(II) ions were 0.38 and 1.85 μg/L, respectively with a preconcentration factor of 100. The recovery % of the extracted Cd(II) and Zn(II), is greater than 90% and the relative standard deviation(RSD,%) is less than 5%.

Development of cloud-point extraction method for preconcentration of trace quantities of cobalt and nickel in water and food samples

A new, efficient, and sensitive cloud point methodology was developed for preconcentration of trace quantities of cobalt and nickel in water and food samples.

Development of novel simultaneous single step and multistep cloud point extraction method for silver, cadmium and nickel in water samples

A novel, simple and rapid single and multi-step cloud point extraction procedure was developed for the selective and simultaneous preconcentration of silver, cadmium and nickel in real samples prior to their determination by flame atomic absorption spectrometry. Dithizone was used as neutral hydrophobic complexing agent. Separation of understudy metals can be achieved by controlling the pH value of the extraction system. Evaluation of the two CPE methods was checked by paired t-test, which indicated a non-significant difference. It was successfully applied to the real water sample. Certified reference materials were used for the accuracy of the green extraction methods. The regression equation for the calibration curve was linear in the range of 10–150μgL−1 for Ag, 5–100μgL−1 for Cd, 10–200μgL−1 for Ni. Relative standard deviation (RSD%) values were found to be lower than 2.5% for all elements. Enhancement factor (EF) and limit of detection (LOD) values were found in the range of 41–58 and 0.27–1.12μgL−1, respectively.

Simultaneous determination of antimony and boron in beverage and dairy products by flame atomic absorption spectrometry after separation and pre-concentration by cloud-point extraction

ABSTRACTA new cloud-point extraction (CPE) method was developed for the pre-concentration and simultaneous determination of Sb(III) and B(III) by flame atomic absorption spectrometry (FAAS). The method was based on complexation of Sb(III) and B(III) with azomethine-H in the presence of cetylpyridinium chloride (CPC) as a signal-enhancing agent, and then extraction into the micellar phase of Triton X-114. Under optimised conditions, linear calibration was obtained for Sb(III) and B(III) in the concentration ranges of 0.5–180 and 2.5–600 μg l−1 with LODs of 0.15 and 0.75 μg l−1, respectively. Relative standard deviations (RSDs) (25 and 100 μg l−1 of Sb(III) and B(III), n = 6) were in a range of 2.1–3.8% and 1.9–2.3%, respectively. Recoveries of spiked samples of Sb(III) and B(III) were in the range of 98–103% and 99–102%, respectively. Measured values for Sb and B in three standard reference materials were within the 95% confidence limit of the certified values. Also, the method was used for the speciation of inorganic antimony. Sb(III), Sb(V) and total Sb were measured in the presence of excess boron before and after pre-reduction with an acidic mixture of KI-ascorbic acid. The method was successfully applied to the simultaneous determination of total Sb and B in selected beverage and dairy products.