Cloud Point Extraction Method Research Articles

LC/MS Method Using Cloud Point Extraction for the Determination of Permitted and Illegal Food Colors in Liquid, Semiliquid, and Solid Food Matrixes: Single-Laboratory Validation

A cloud point extraction method is reported using LC/MS for the determination of regulated water-soluble food colors (Allura Red, Sunset Yellow, erythrosine, and tartrazine) and banned fat-soluble synthetic azo dyes (Sudan I, II, III, and IV; Red B; 7B; Black B; Red G; Metanil Yellow; and Rhodamine B). The extraction of all 14 colors was carried out with cloud point extraction using the nonionic surfactant Triton X 114. Optimized conditions for cloud point extraction were 3% Triton X 114 (w/v), 0.1 M ammonium acetate, and heating at 50 degrees C for 30 min. This approach proved effective in giving quantitative recoveries from a diverse range of food matrixes, and optimized LC gave baseline chromatographic separation for all colors including Sudan IV and Red B. Single-laboratory validation was performed with spiking into liquid matrixes (wine and homemade wine), semiliquid matrixes (sauce and homemade paprika paste), and solid matrixes (spice and homemade chili powder) using the respective blank matrixes for matrix-matched calibration. The LOQ values for water-soluble colors were in the range of 15-150 mg/kg, and for the fat-soluble colors, 0.1-1.5 mg/kg. The mean recovery values were in the range of 69.6-116.0% (except Allura Red and Sunset Yellow in wine, for which recoveries were lower). The mean RSDs for colors were in the range of 4.0-14.8%. A small survey was conducted of samples of confectionery products, dried fruits, wines, bitter sodas, juices, sauces, pastes, and spices, which demonstrated the applicability of the method to a diverse selection of real food samples. Allura Red was detected in strawberry jelly and Sunset Yellow in artificial saffron.

Determination of formaldehyde in beer based on cloud point extraction using 2,4-dinitrophenylhydrazine as derivative reagent

A cloud point extraction method was developed for extraction of formaldehyde in beer prior to high performance liquid chromatography analysis. The formaldehyde was taken into complex with 2,4-dinitrophenylhydrazine in aqueous nonionic surfactant Triton X-114 medium and concentrated in the surfactant-rich phase by bringing the solution to the temperature of 60°C. Under optimal conditions, the limit of detection of formaldehyde is 0.7ngmL−1. The intra- and inter-day precisions expressed as relative standard deviations are 4.2% and 5.5%, respectively. The proposed method was successfully applied for determination of formaldehyde in various beer samples. The contents of formaldehyde in these samples are in the range of 172–385ngmL−1. The results were in agreement with those obtained by the state standard method (steam-distillation and spectrophotometry analysis) used in China. The developed method was demonstrated to be rapid and sensitive for extraction and determination of formaldehyde in beer.

Cloud point extraction for determination of Diazinon: Optimization of the effective parameters using Taguchi method

Since Diazinon is one of the organophosphorous compounds which are harmful for human organisms, a simple, sensitive and accurate testing method for extraction and determination of this pesticide is mandatory. In this project, Cloud Point Extraction (CPE) method was developed for determination of Diazinon in aqueous samples. CTAB (cetyl trimethyl ammonium bromide) was used as cationic surfactant to extract and preconcentrate of Diazinon at the same time and the extracted Diazinon was determined by UV spectrophotometery. Taguchi L 9 array was employed for design of experiments to investigate influences of surfactant concentration, salt concentration, temperature and incubation time as effective parameters. According to the analysis of variance (ANOVA) results, the most effective parameter of the process is incubation time. The results show that a surfactant concentration of 10 − 5 % (w/v), an incubation time of 30 min, a KI concentration of 10 − 6 mol L − 1 and a temperature of 35 °C are the best operating conditions. Also, the linear calibration graph in the range of 0.02–24 ng ml − 1 of Diazinon with r = 0.999 was obtained. The limit of detection (LOD) was 0.02 ng ml − 1 and relative standard deviation (RSD) for 15 ng ml − 1 of Diazinon was 0.76%.

Determination of Anthraquinone Derivatives in Chang-Qing Tea by Using Cloud-Point Extraction and High-Performance Liquid Chromatography

In this paper, a cloud-point extraction method was developed for the determination of five anthraquinone derivatives in Chang-Qing tea by high-performance liquid chromatography. The optimum conditions for micelle extraction were obtained as follows—15% (w/v) Genapol X-080 as extractant, pH 3.5, liquid/solid ratio 80, and extraction time, 40 min. For cloud point preconcentration, 20% (w/v) NaCl was added, and the solution was incubated at 55 °C for 30 min. The detection limits for the five anthraquinone derivatives were in the range of 0.55–3.30 ng ml−1. Average recoveries for the anthraquinone derivatives at three spiked levels were in the range of 84.3–104.1%. Relative standard deviations for six replicate determinations of Chang-Qing tea sample were below 2.39. The established method has been successfully applied to the determination of anthraquinone derivatives in Chang-Qing tea products from three different manufacturers.

Multivariate optimization of cloud point extraction procedure for zinc determination in aqueous extracts of medicinal plants by flame atomic absorption spectrometry

Cloud point extraction method has been developed for preconcentration of trace quantities of zinc (Zn) in aqueous extract of medicinal plants and blood samples of liver cancer patients using flame atomic absorption spectrometry. The Zn in aqueous extracts of medicinal plants (MPs) was complexed with 2-methyl-8-hydroxyquinoline (quinaldine) and 1-(2-pyridylazo)-2-naphthol (PAN) separately and entrapped in a non-ionic surfactant Triton X-114. After centrifugation, the surfactant-rich phase was diluted with 0.25mL acidic ethyl alcohol. The multivariate strategy was applied to estimate the optimum values of experimental variables (pH, time temperature, ligands and surfactant concentrations). Interactions between analytical factors and their optimal levels were investigated by two level factorial designs. Student’s t-test on the results of factorial design with 16 runs for Zn extraction, demonstrated that the factors, ligands concentrations, pH and temperature were statistically significant. The accuracy was assessed by analysis of certified reference materials, namely, BCR 101 (spruce needles), Clincheck control-lyophilized human whole blood. Enhancement factor of 30 and 26 were achieved for the preconcentration of Zn by 2-methyl-8-hydroxyquinoline (L1) and 1-(2-pyridylazo)-2-naphthol (L2), respectively. The relative standard deviation for six replicate determinations of Zn at 10μg/L level using 2-methyl-8-hydroxyquinoline (L1) and 1-(2-pyridylazo)-2-naphthol (L2) were <4% and >5%, respectively.

Flame atomic absorption spectrometric determination of trace amounts of palladium, gold and nickel after cloud point extraction

In this article, a sensitive cloud point extraction procedure for the preconcentration of trace amounts of palladium, gold and nickel prior to their determination by flame atomic absorption spectrometry has been developed. The cloud point extraction method is based on the complexation of Pd(II), Au(II), and Ni(II) ions with 1-(2-pyridylazo)-2-naphthol and entrapping in non-ionic surfactant Triton X-114. The main factors affecting cloud point extraction efficiency, such as pH of sample solution, concentration of 1-(2-pyridylazo)-2-naphthol and Triton X-114, equilibration temperature and time, were investigated in detail. Under the optimized conditions, calibration curves were constructed for the determination of palladium, gold and nickel according to the general procedure. Linearity was maintained from 0.01 to 1.0 μg/mL for palladium, 10.0 μg/mL to 1.5 μg/mL for gold, and 10.0 μg/mL to 0.5 μg/mL for nickel. Detection limits based on three times the standard deviation of the blank divided by the slope of analytical curve (3Sb/m) for Pd(II), Au(III), and Ni(11) ions were 3.4, 3.9, and 2.4 μg/mL, respectively. Seven replicate determination of a mixture of 0.5 μg/mL palladium and gold and 0.2 μg/mL nickel gave a mean absorbance of 0.174, 0.150, and 0.201 with relative standard deviation ±1.5, ±1.3, and ±1.8%, respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed method has been applied for determination of trace amount of palladium, gold and nickel in certified reference material and water samples with satisfactory results.

Determination of Vanadium in Food Samples by Cloud Point Extraction and Graphite Furnace Atomic Absorption Spectroscopy

A preconcentration methodology utilizing the cloud point phenomenon is described for the determination of total vanadium by graphite furnace atomic absorption spectrometry. Cloud point extraction method was based on the formation of a ternary complex between vanadium, 2-(2´-thiazolylazo)-p-cresol, and ascorbic acid, with subsequent extraction–preconcentration of the formed complexes using Triton X-100. Optimization of different parameters was evaluated. Under optimal conditions, a calibration curve was constructed, showing a linear range of 1.0–60 ng mL−1 and the limit of detection and relative standard deviation for preconcentration of a 10-mL sample were found to be 0.05 ng mL−1 and 3.9%, respectively. The preconcentration factor was found to be tenfold for 10 mL of water sample. The technique has been applied succesfully to the determination of vanadium traces in wine, tea, and tomato samples and the recoveries of added vanadium were in the range 96–102%.

Development of a cloud point extraction and preconcentration method for determination of trace aluminum in mineral waters by FAAS

A cloud point extraction (CPE) method has been developed for the preconcentration of trace aluminum prior to its determination by flame atomic absorption spectrometry (FAAS). The CPE method is based on the complex of Al(III) with Xylidyl Blue (XB) and then entrapped in non-ionic surfactant Triton X-114. The main factors affecting CPE efficiency, such as pH of sample solution, concentration of XB and Triton X-114, equilibration temperature and time, were investigated in detail. An enrichment factor of 50 was obtained for the preconcentration of Al(III) with 50mL solution. Under the optimal conditions, the detection limit of this method for Al(III) is 1.43μgL−1, and the relative standard deviation is 2.7% at determination of 100μgL−1 Al(III). The proposed method has been applied for determination of trace amount of aluminum in mineral water samples with satisfactory results. Also, the proposed method was applied to the certified reference materials. The results obtained were in good agreement with certified values.

Determination of Vitamins A and E Exploiting Cloud Point Extraction and Micellar Liquid Chromatography

Cloud point extraction and micellar chromatographic methods were developed for determination of vitamins A and E. The stationary phase was C18 and the mobile phase was 3.00% (w/v) SDS, 15.0% (v/v) butyl alcohol and 0.02 mol L−1 phosphate buffer solution at pH 7.0. The retention times for vitamins A and E were 9.6 and 13.0, respectively. The extraction solution was 100 mmol L−1 Triton X-100, 650 mg NaCl and 1.0% ascorbic acid at 70°C for 30 min. The method is precise (r.s.d. < 7%), the linear range was from 5.0 up to 360.0 mg L−1 for both vitamins. Recovery test showed recuperation between 90.2 and 99.2%, and LOD and LOQ of 0.234 and 0.108 mg L−1, 0.780 and 0.360 mg L−1 to vitamins A and E were found.

Simultaneous cloud point extraction and spectrophotometric determination of carmoisine and brilliant blue FCF in food samples

A novel simultaneous cloud point extraction method for the determination of carmoisine and brilliant blue FCF by spectrophotometry has been developed. The method is based on the cloud point extraction of carmoisine and brilliant blue FCF from aqueous solution using Triton X-100, diluting the extracted surfactant rich phase with water and measuring the absorbance at 522 and 640 nm for carmoisine and brilliant blue FCF, respectively. The effects of different parameters such as pH, concentration of surfactant and temperature on the cloud point extraction of both dyes were investigated and optimum conditions were established. Linear calibration curves were obtained in the range of 0.02–3.50 μg mL −1 for carmoisine and 0.05–3.50 μg mL −1 for brilliant blue FCF under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S b) was 0.017 and 0.016 μg mL −1 ( n = 10) for carmoisine and brilliant blue FCF, respectively. The relative standard deviation (RSD) for 0.1 μg mL −1 was 4.14 and 3.30% ( n = 10), for carmoisine and brilliant blue FCF, respectively. The method was applied to the simultaneous determination of the dyes in different food samples.

Speciation and preconcentration of iron by cloud point extraction combined with fibre optic linear array detection spectrophotometry

A highly selective method for speciation and preconcentration of iron was developed using cloud point extraction (CPE) combined with fibre optic-linear array detection spectrophotometry (FO-LADS). Cloud point extraction method was based on the chromogenic reaction of Fe(II) and Fe(III) with 1-(2-pyridylazo)-2-naphthol (PAN) and then preconcentration of formed complexes using octylphenoxy polyethoxy ethanol (Triton X-114). When the system temperature is higher than the cloud point extraction temperature (CPT) of selected surfactant, the complex of Fe(II) with 1-(2-pyridylazo)-2-naphthol (PAN) could enter surfactant-rich phase, whereas the complex of Fe(III) remained in aqueous phase. Thus, an in situ separation of Fe(II) and Fe(III) could be realized. An iron complex in the surfactant-rich phase was determined by fibre optic-linear array detection spectrophotometry.The main factors affecting the cloud point extraction, such as pH, concentration of (PAN) and Triton X-114, equilibration temperature and time, were investigated systematically. Under the optimized conditions, the enhancement factors of 167 and 158 were obtained for Fe(II) and Fe(III) respectively, the limits of detection (LOD) was 0.2 μg L−1 for Fe(II) and 0.5 μg L−1 for Fe(III). The relative standard deviations (n = 5, c = 40.0μg L−1) was lower than 3%. The proposed method is highly selective without any interference ions. This method was successfully applied to the speciation of iron in different samples with satisfactory results.

Cloud‐Point Extraction and Reversed‐Phase High‐Performance Liquid Chromatography for the Determination of Synthetic Phenolic Antioxidants in Edible Oils

A cloud-point extraction (CPE) method using Triton X-114 (TX-114) nonionic surfactant was developed for the extraction and preconcentration of propyl gallate (PG), tertiary butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) from edible oils. The optimum conditions of CPE were 2.5% (v/v) TX-114, 0.5% (w/v) NaCl and 40 min equilibration time at 50 °C. The surfactant-rich phase was then analyzed by reversed-phase high-performance liquid chromatography with ultraviolet detection at 280 nm, using a gradient mobile phase consisting of methanol and 1.5% (v/v) acetic acid. Under the studied conditions, 4 synthetic phenolic antioxidants (SPAs) were successfully separated within 24 min. The limits of detection (LOD) were 1.9 ng mL(-1) for PG, 11 ng mL(-1) for TBHQ, 2.3 ng mL(-1) for BHA, and 5.9 ng mL(-1) for BHT. Recoveries of the SPAs spiked into edible oil were in the range 81% to 88%. The CPE method was shown to be potentially useful for the preconcentration of the target analytes, with a preconcentration factor of 14. Moreover, the method is simple, has high sensitivity, consumes much less solvent than traditional methods, and is environment-friendly. Practical Application: The method established in this article uses less organic solvent to extract SPAs from edible oils; it is simple, highly sensitive and results in no pollution to the environment.

Application of ionic-liquid supported cloud point extraction for the determination of microcystin-leucine–arginine in natural waters

A cloud point extraction method has been developed using an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, BMiM PF 6) for the determination of a widely studied cyanotoxin (microcystin leucine–arginine, MCLR) in natural waters. Extraction parameters such as sample pH, extraction temperature, extraction time, the amount of ionic liquid and the amount of extraction volume were investigated and optimized to achieve the maximum extraction efficiency. The results obtained indicated a good linearity with the correlation coefficient of 0.995 over the range of 0.5–50 μg L −1. The relative standard deviation (RSD) of the method was 7.5% ( n = 6). The calculated method detection limit was 0.03 μg L −1 ( n = 6). The practical applicability of the technique was demonstrated by analyzing water samples ( n = 9) collected from three different sites in local reservoirs.

Determination of trace bismuth in human serum by cloud point extraction coupled flow injection inductively coupled plasma optical emission spectrometry

A cloud point extraction method for the preconcentration of ultra-trace bismuth in human serum prior to its determination by inductively coupled plasma optical emission spectrometry had been developed in this paper. The cloud point extraction method was based on the complex of Bi(III) with 8-hydroxyquinoline and Triton X-114 was used as non-ionic surfactant. The main factors affecting cloud point extraction efficiency, such as pH of solution, concentration of complexing agent, concentration of non-ionic surfactant, equilibration temperature and time were investigated in detail. An enrichment factor of 81 was obtained for the preconcentration of Bi(III) with 25 mL solution. Under the optimal conditions, the detection limit of Bi(III) is 0.12 μg L −1. The relative standard deviation ( n = 7) of determination was 2.3%, values of recovery of bismuth were from 92.3% to 94.7% for three samples. This method is simple, accurate, sensitive and can be applied to the determination trace bismuth in human serum.

Simplified cloud point extraction-inductively coupled plasma mass spectrometry for the preconcentration/analysis of ultra-trace gold

A new cloud point extraction method for the preconcentration of ultra-trace gold as a prior step to its determination by inductively coupled plasma mass spectrometry (ICP-MS) has been developed. The method is based on the cloud point extraction (CPE) of gold in the non-ionic surfactant Triton X-114 without a chelating agent. The parameters of CPE were investigated in detail. At optimum conditions, the linear range of 5.0–200.0 ng L −1 of Au(III) and the detection limits of 1.1 ng L −1 for Au(III) along with enrichment factors of 7.5, were obtained. The proposed method was applied to determination of ultra-trace amounts of gold in water samples with satisfactory results.

MICELLE-MEDIATED EXTRACTION AS A TOOL FOR SEPARATION AND PRECONCENTRATION IN COPPER ANALYSIS

A cloud point extraction method was presented for preconcentration of copper in various samples. After complexation with 4-Amino-2,3-dimethyl-1-phenyl-3-pyrazoline-5-one (ADPP) or N-Benzoyl-N-phenylhydroxylamine (BPA) in water, analyte ions are quantitatively extracted to the phase rich in Triton X-114 after centrifugation. 2.0 mol L-1 HNO3 solution in methanol was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The adopted concentrations for ADPP, Triton X-114, HNO3 and parameters such as bath temperature, centrifuge rate and time were optimized. Detection limits (3SDb/m) of 1.3 and 1.9 ng mL-1 for ADPP and BPA along with enrichment factors of 30 and 38 for ADPP and BPA were achieved. The high efficiency of cloud point extraction to carry out the determination of analyte in complex matrices was demonstrated. The proposed method was applied to the analysis of biological, industrial, natural and wastewater, soil and blood samples. Keywords: 4-Amino-2,3-dimethyl-1-phenyl-3-pyrazoline-5-one (ADPP), N-Benzoyl-N-phenylhydroxylamine (BPA) , Cloud Point Extraction, Triton X-114, Flame Atomic Absorption Spectrometry.

Cloud point extraction of vanadium in pharmaceutical formulations, dialysate and parenteral solutions using 8-hydroxyquinoline and nonionic surfactant

A cloud point extraction (CPE) method has been developed for the determination of trace quantity of vanadium ions in pharmaceutical formulations (PF), dialysate (DS) and parenteral solutions (PS). The CPE of vanadium (V) using 8-hydroxyquinoline (oxine) as complexing reagent and mediated by nonionic surfactant (Triton X-114) was investigated. The parameters that affect the extraction efficiency of CPE, such as pH of sample solution, concentration of oxine and Triton X-114, equilibration temperature and time period for shaking were investigated in detail. The validity of CPE of V was checked by standard addition method in real samples. The extracted surfactant-rich phase was diluted with nitric acid in ethanol, prior to subjecting electrothermal atomic absorption spectrometry. Under these conditions, the preconcentration of 50 mL sample solutions, allowed raising an enrichment factor of 125-fold. The lower limit of detection obtained under the optimal conditions was 42 ng/L. The proposed method has been successfully applied to the determination of trace quantity of V in various pharmaceutical preparations with satisfactory results. The concentration ranges of V in PF, DS and PS samples were found in the range of 10.5–15.2, 0.65–1.32 and 1.76–6.93 μg/L, respectively.

Preconcentration and determination of iron and copper in spice samples by cloud point extraction and flow injection flame atomic absorption spectrometry

A flow injection (FI) cloud point extraction (CPE) method for the determination of iron and copper by flame atomic absorption spectrometer (FAAS) has been improved. The analytes were complexed with 3-amino-7-dimethylamino-2-methylphenazine (Neutral Red, NR) and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant. The micellar solution was heated above 50 °C and loaded through a column packed with cotton for phase separation. Then the surfactant-rich phase was eluted using 0.05 mol L −1 H 2SO 4 and the analytes were determined by FAAS. Chemical and flow variables influencing the instrumental and extraction conditions were optimized. Under optimized conditions for 25 mL of preconcentrated solution, the enrichment factors were 98 and 69, the limits of detection (3 s) were 0.7 and 0.3 ng mL −1, the limits of quantification (10 s) were 2.2 and 1.0 ng mL −1 for iron and copper, respectively. The relative standard deviation (RSD) for ten replicate measurements of 10 ng mL −1 iron and copper were 2.1% and 1.8%, respectively. The proposed method was successfully applied to determination of iron and copper in spice samples.

Elimination of fuel spills from effluent using cloud point extraction methods

Cloud point extraction procedure was used to remove hydrocarbons from aqueous streams coming from fuels storage centre. This real effluent was characterized by a high chemical oxygen demand (COD = 7000 mg O 2/L) due to significant concentration of hydrocarbons as gasoline diesel and kerosene. Two biodegradable non-ionic surfactants (Lutensol AO7 and Triton X-114) were employed to treat this effluent. First, the phase diagrams of the binary systems, water–surfactant and the pseudo-binary system, water–surfactant–hydrocarbons were determined. The effect of sodium sulphate on water–surfactant–hydrocarbons systems was studied. The experimental results, with respect to surfactant wt.% and temperature, were expressed in term of residual (soluble) chemical oxygen demand (COD S), residual concentrations of surfactant in the dilute phase ( X t,w ) converted to chemical oxygen demand (COD TA) and the volume fraction of coacervate ( ϕ C) at the equilibrium. The results obtained for each parameter were represented on three-dimensional diagrams using an empirical fitting method. For instance, COD can be decreased from 7000 mg O 2/L to 50 mg O 2/L and 30 mg O 2/L, using Triton X-114 and Lutensol AO7, respectively at room temperature. However, the extraction extent of such effluent was found to be low at basic pH, which may be useful for surfactant regeneration.

Determination of trace quantity of aluminium in dialysate concentrates using solid phase and cloud point extraction methods

A new method is reported for the separation of aluminium ions (Al3+) from interfering cations in dialysis concentrate solutions (DS) through solid phase extraction (SPE) using 2-methyl-8-hydroxyquinoline (2-MHQ). While separated Al3+ was preconcentrated by cloud point extraction (CPE) using 8-hydroxyquinoline (8-HQ) as complexing reagent, the resulting complex was entrapped in non-ionic surfactant (Triton X-114). Then fluorescence intensity of the Al3+-8-HQ complex was measured by spectrofluorimetry and the results were compared with those obtained by flame atomic absorption spectrometry. The chemical variables affecting the analytical performance of the CPE were studied and optimized. The validity of methodology was checked by the standard addition method, under optimum experimental conditions >98% recovery of Al3+ was obtained. The enrichment factor and detection limit of Al3+ for the preconcentration of 50 ml of DS were found to be 200 and 0.384 μg L−1, respectively. The relative standard deviation for six replicate determinations of Al3+ at a concentration level of 50 μg L−1 for both techniques was <6%. The effect of different interferent species was also studied. The proposed method has been applied for the determination of trace amount of Al3+ in DS samples with satisfactory results. The concentration of Al3+ in DS was observed in the range of 15.2–43.8 μg L−1, which is above the permissible limit.