Surfactant-rich Phase Research Articles

Development of a Precolumn Derivatization Procedure Prior to Ultrasound-Assisted Cloud Point Extraction for Sensitive Determination of Fluoroquinolones in Eggs by High-Performance Liquid Chromatography with Fluorescence Detection

In this work, a 4-chloro-7-nitrobenzodioxazole (NBD-Cl) derivatization coupled with the ultrasound-assisted cloud point extraction (UACPE) method prior to high-performance liquid chromatography with fluorescence detection (HPLC-FLD) analysis was developed for the determination of four widely used fluoroquinolones (FQs) including norfloxacin (NOR), ciprofloxacin (CIP), sarafloxacin (SAR), and gatifloxacin (GAT) in eggs. The derivatives of FQs with NBD-Cl were extracted into the Triton X-114 surfactant-rich phase, which was analyzed by reversed-phase HPLC-FLD. Ultrasound was applied to accelerate the phase separation in extraction and enhance the extraction efficiency of target analytes. Variable parameters affecting the derivatization and UACPE procedure were systematically evaluated and optimized. Under the optimum conditions, four FQs were successfully separated within 30 min through an Agilent TC-C18 column. Good recoveries of 86.2–103.5 %, which were calculated using a range of spiked samples at three concentrations, were obtained by UACPE. The calibration graphs were linear over the range of 1.2–73.0 μg kg−1 for four FQs with correlation coefficients (R) no less than 0.9957. The limits of detection were 0.2, 0.5, 0.3, and 0.4 μg kg−1 for NOR, CIP, SAR, and GAT, respectively. The precisions indicated by relative standard deviations ranged from 0.6 to 4.3 % for both intraday and interday analysis. The proposed method proved to be a selective, sensitive, and eco-friendly approach which was successfully applied to analyze FQs in eggs at the local farmers market, and none of the target analytes were detected in these samples.

Cloud-point extraction, preconcentration and spectrophotometric determination of trace quantities of copper in food, water and biological samples

A new, simple and sensitive cloud point extraction procedure was presented for the preconcentration and determination of copper(II) ion in food, water and biological samples. The analyte was complexed with a new synthesized reagent, 2-amino-4-(m-tolylazo)pyridine-3-ol (ATAP) as a new complexing agent and Triton X-114 as the surfactant. After centrifugation, dilution of the surfactant-rich phase with 0.4mL of ethanol acidified with 1.0M HNO3 was performed after phase separation, and the copper contents were measured by spectrophotometry at λmax 608nm. The influence of analytical parameters including concentration of complexing agent, Triton X-114, pH, equilibration temperature and time, centrifuge rate and time were optimized. The analytical characteristics of the method (e.g. linear range, molar absorptivity, Sandell sensitivity, optimum Ringbom concentration ranges limits of detection and quantification, preconcentration factor, and improvement factors) were obtained. Linearity was obeyed in the range of 4.0–115ngmL−1 of Cu(II) ion. The detection and quantification limits of the method were 1.20 and 3.94ngmL−1 of Cu(II) ion, respectively. The interference effect of some anions and cations was also tested. The method was applied for determination of copper in food, water and biological samples.

Cloud Point Extraction and Spectrophotometry Determination of Lead in Environment Water Using 5-Br-PADAP

A simple, sensitive, green and low cost detection method based on the cloud point extraction (CPE) separation and spectrophotometry was proposed for the determination of lead. In pH=9.0 H3BO3 buffer solution, Pb(II) reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in the presence of Triton X-100 yielding a hydrophobic complex, which then is extracted into micro-volume surfactant-rich phase. The calibration graph was linear in the range of 20-400 µg/L (at 560 nm). Under the optimized conditions, the detection limits of 10.94 µg/L and the relative standard deviations(RSD) of 2.0% (n=5) for Lead(II) were found, respectively. The sensitivity and absorbance of this method are at least five times higher when compared with that of usual 5-Br-PADAP spectrophotometry without CPE, and the proposed method has been applied to the determination of Lead in environment water samples with satisfactory results.

Preconcentration of toxic elements in artificial saliva extract of different smokeless tobacco products by dual-cloud point extraction

Smokeless tobacco (SLT) has been associated with oral cancer. In present study, the total and artificial saliva extracted toxic elements (TEs), arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) were estimated in SLT products (gutkha, green and brown snuff). Dual-cloud point extraction has been used for the preconcentration of As, Cd, Ni and Pb in artificial saliva extract, using complexing reagent, ammonium pyrrolidinedithiocarbamate. The dual-cloud point extraction procedure was based on forming complexes of elemental ions with complexing reagent and subsequent entrapping of the complexes in nonionic surfactant. Then the surfactant rich phase containing the complexes was treated with nitric acid, and detected ions were back extracted again into aqueous phase at the second cloud point extraction stage, and finally determined by electrothermal atomic absorption spectrometry. The validity of methodology was tested by simultaneously analyzing certified reference material and spike recovery test. The experimental enhancement factors of As, Cd, Ni and Pb were found to be 52, 58, 48 and 44, respectively. The concentration of As, Cd, Ni and Pb in artificial saliva extracts corresponds to 18–24, 45–75, 30–55, and 20–30%, respectively, of the total contents of TE in different types of SLT products (gutkha, brown and green snuff). It was estimated that 10g intake of SLT products (gutkha, brown and green snuff) could contribute 2.2–13, 21–69, 3.4–48 and 10–75% of the provisional maximum tolerable daily intake of As, Cd, Ni and Pb, respectively for adults ~60kg.

Cloud point extraction of Cu(II) using a mixture of triton X-100 and dithizone with a salting-out effect and its application to visual determination

A method for the separation and concentration of trace copper(II) ion (Cu(II)) via cloud point extraction (CPE) using a nonionic surfactant with a salting-out effect was developed and applied as a technique for the visual determination of Cu(II). Triton X-100 (TX-100), which has a cloud point at 64-67 °C in aqueous solutions, was used as the nonionic surfactant for the CPE of Cu(II). Although CPE with TX-100 requires heating of the solution to separate the surfactant-rich phase from the aqueous phase, the new method achieves phase separation at 15-30 °C owing to the addition of a large amount of salt to the solution, which lowers the cloud point. The compound 1,5-diphenylthiocarbazone (dithizone) was selected as the chelating agent for complexation and transfer of Cu(II) to the surfactant-rich phase. The extractability of Cu(II) (initial concentration: 10 μM) was 96.6±2.1% when Na2SO4 was added to a 20% TX-100/4 μM dithizone solution (pH 2). Using this method, the visual determination of Cu(II) was possible for concentrations ranging from 0.01 to 10 μM. In addition, the extraction system was successfully applied to the visual determination of Cu(II) in a river water sample.

Evaluation of lead levels in biological samples of mentally retarded children in different stages using advanced extraction method

In present study the lead (Pb) levels has been assessed by analyzing the scalp hair and blood samples of mentally retarded/intellectual disabled (MR/ID) children of both genders, age ranged 3–8 years. For comparative purpose, healthy age matched children were also selected. The cloud point extraction of Pb from digested biological samples was carried out by complexed with ammonium pyrrolidinedithiocarbamate. The complexed analyte was subsequently isolated from the aqueous matrix in the micelles of a non-ionic surfactant (Triton X-114). Dilution of the surfactant-rich phase with acidified ethanol was performed after phase separation, and the Pb content was measured by flame atomic absorption spectrometer. Factors affecting the cloud point extraction were evaluated and optimized. The proposed procedure allowed the determination of lead in certified standard and real samples with detection limits of 0.834μgL− and enhancement factor 55. The results were compared with those of healthy children have same age, socioeconomic status and residential areas.

Determination of manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples by cloud-point extraction and high-performance liquid chromatography

A highly sensitive method for the determination of manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples is proposed. The method is based on analytes reacted with ammonium pyrrolidinedithiocarbamate (APDC) to give hydrophobic chelates (M–APDC), which were separated and enriched by cloud-point extraction (CPE) with non-ionic surfactant Tergitol TMN-6 as extractant. The surfactant-rich phase containing the chelates is determined with a high-performance liquid chromatography system. To achieve the best CPE method, the Box–Behnken design was used to study the concentration of Tergitol TMN-6, equilibrium temperature, equilibrium time as well as their interaction. What followed was the individual research for the pH of the sample solutions and the concentration of APDC. What is more, in the given optimized experimental conditions, calibration plots were found to be linear in the range of 0.0200–0.500 mg/L for Mn (VII) and Cr (VI), meanwhile 0.0500–1.00 mg/L for Ni (II), the linear correlation coefficients were between 0.996 and 0.999, the recoveries ranged from 91.8 to 97.8 % and the relative standard deviations were between 1.09 and 2.30 % (n = 3). The limits of detection were 0.164 μg/L for Mn (VII), 0.562 μg/L for Cr (VI) and 5.12 μg/L for Ni (II), respectively. The proposed method was applied to determine manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples with satisfactory results.

Preconcentration and determination of lead(II) by microextraction based on suspended cadion covered zirconia nanoparticles in a surfactant media

We have developed a method for the microextraction of lead(II) ion. It is based on the use of suspended zirconia nanoparticles modified with the reagent cadion. Pb(II) ions in the sample are adsorbed onto the modified zirconia nanoparticles suspended in the solution of a non-ionic surfactant. After cloud formation and phase separation by sedimentation, the surfactant rich phase was acidified and diluted to 100 μL with 3.0 mol L−1 nitric acid and ultrasonicated for a few seconds to desorb the analyte from the sorbent. The mixture was centrifuged and 10 μL of the supernatant liquid phase along with 10 μL of the Pd/Mg modifier were submitted to the electrothermal atomic absorption spectrometer. The parameters affecting the extraction efficiency were optimized by the univariable method. Under the optimized conditions, a sample volume of 40 mL resulted in an enhancement factor of 384 and a detection limit (defined as 3Sb/m) of 2.2 ng L−1. The method was successfully applied to the determination of Pb(II) in water, tea and rice samples. Accuracy was determined by the recovery experiments and the analysis of two certified reference materials.

Purification of a novel protease enzyme from kesinai plant (Streblus asper) leaves using a surfactant–salt aqueous micellar two-phase system: a potential low cost source of enzyme and purification method

Serine protease from kesinai leaves was purified for the first time by a surfactant–polymer aqueous micellar two-phase system. The effectiveness of different types and concentrations of non-ionic surfactants (Pluronic series and X-114) on the partitioning behaviour of the protease was evaluated. The results showed that the enzyme preferentially partitioned into the bottom surfactant-rich phase, while the hydrophilic amino acid preferred the top aqueous phase. This distribution of the enzyme is due to the hydrophobic interaction of the serine protease with the hydrophobic lid of the micelle core in the bottom phase. The influence of different types of salts (K2SO4, KH2PO4, KCl and KNO3) on the purification and selectivity of the enzyme was determined. The protease partitioning in the bottom phase increased in the presence of KNO3, which confirmed that the salt was able to improve the protein solubility in bottom phase and increase the hydrophobic interaction between the two phases. In addition, the protease from the bottom phase was re-extracted to a new aqueous phase solution to remove and recycle the surfactant. Addition of potassium thiocyanate led to the partitioning of the enzyme in top aqueous phase due to high ionic strength of SCN−, which forced the lighter micellar phase toward the upper position of the system. A high purification factor (10.3) and yield of 92 % of the enzyme were achieved in a solution of 31 % of Pluronic L61 using 0.3 % KNO3 and 50 % crude feedstock at pH 7.0.

Cloud Point Extraction (CPE) of Parabens using Nonionic Surfactant Phase Separation

A cloud point extraction (CPE) method was developed using silicone-ethylene oxide surfactant, DC193C, to study the equilibrium phase separation of parabens in environmental water samples. The volume of the surfactant rich phase (Vs), aqueous phase (Vw), preconcentration factor (CF), distribution coefficient (Kd), and percentage of recovery (%R) were evaluated to obtain the optimum condition for phase separation of parabens. Satisfactory results were obtained whereby the preconcentration factor for methylparaben, ethylparaben, propylparaben, and benzylparaben were close to 65, 60, 80, and 45, respectively, at 0.5% weight of surfactant. The presence of DC193C gave a low phase volume ratio but insignificant result was observed with the increased of surfactant concentration. The parabens were well separated on a reverse-phase Chromolith C18 column (100 mm × 4.6 mm) with a gradient elution (acetonitrile: water; 30:70 v/v) and detected at 254 nm. The proposed method was successfully applied to environmental samples such as river water, treated wastewater, sea water, and tap water with satisfactory results. The method detection limit was 0.1–0.2 ppb and the recoveries were 71.2–97.7% with the relative standard deviations of 0.3–2.1%.

Micelle-Mediated Extraction Prior to LC-UV for Preconcentration and Determination of Trace Amounts of Bisphenol A in Environmental Samples

A simple and high sensitive preconcentration method based on micelle-mediated extraction followed by high performance liquid chromatography (LC-UV) was developed for preconcentration and determination of trace amounts of bisphenol A (BPA) in aqueous samples. The BPA was quantitatively extracted from aqueous samples in the presence of Triton X-114 as a nonionic surfactant and preconcentrated into the small volume (about 30 μL) of the surfactant-rich phase. Taguchi method, an orthogonal array design (OA16 (45)), was utilized to optimize the various factors affecting the micellar extraction of BPA. The maximum extraction efficiency of BPA was obtained at pH 3, 0.2% (w/v) Triton X-114, and 0.25 mol L−1 sodium acetate. For the preconcentration, the solutions were incubated in a thermostatic water bath at 50°C for 7 min. After centrifuge and separation of aqueous phase, the surfactant-rich phase was diluted with 100 μL acetone and injected in the chromatographic system. Under the optimum conditions, preconcentration factor of 34.9 was achieved for extraction from 10 mL of sample solution and the relative standard deviation (RSD%) of the method was lower than 6.6%. The calibration curve was linear in the range of 0.5–150 μg L−1 with reasonable linearity (r2>0.9987). The limit of detection (LOD) based on S/N = 3 was 0.13 μg L−1 for 10 mL sample volumes. The limit of quantification (LOQ) based on S/N = 10 was 0.43 μg L−1 for 10 mL sample volumes. Finally, the applicability of the proposed method was evaluated by the extraction and determination of BPA in the real samples, and satisfactory results were obtained.

Cloud point extraction for the determination of trace copper(II) in environmental samples using a new synthesized reagent and flame atomic absorption spectrometry

Cloud point extraction for the determination of copper(II) is proposed after the formation of a complex with sulfapyridylazo resorcinol (SPAR) and later measurement by flame atomic absorption spectrometry (FAAS) using Triton X-100 as a surfactant. The surfactant-rich phase was diluted with nitric acid in methanol, prior to FAAS measurement. Analytical parameters including pH, concentration of the chelating agent and surfactant, equilibration temperature and time were optimized. The effects of matrix ions on the recovery of copper ions were also studied. A detection limit of 1.64 μg L−1 along with an enrichment factor of 31 for Cu were achieved. The method was successfully applied to the determination of copper in tap water, stream water, rain water and a standard reference material.

Coacervative extraction of trace lead from natural waters prior to its determination by electrothermal atomic absorption spectrometry

In this work, a relatively simple and sensitive method for separation/preconcentration of trace lead from natural waters prior to its determination by electrothermal atomic absorption spectrometry has been proposed. The method is based on the extraction of Pb–dithizone chelate with coacervates made up of lauric acid in the presence of potassium ions and methanol. Several important factors affecting extraction efficiency such as pH, concentration of lauric acid and dithizone, ionic strength, incubation and centrifugation time were investigated and optimized. After separation of aqueous bulk solution from surfactant-rich phase, the final extract was redissolved by using 500μl of methanol acidified with 0.2moll−1 HNO3. Under the optimized conditions (using initial sample volume of 10ml), enrichment factor of 17.0, detection limit of 0.12μgl−1, quantification limit of 0.38μgl−1, relative standard deviation of 4.2% (for 2μgl−1 of Pb; n=26), linearity of the calibration graph in the range of 0.5–4.0μgl−1 (with correlation coefficient better than 0.995) were achieved. The method was validated by the analysis of certified reference material (TMDA-61). Extraction recoveries for the CRM, spiked model solutions and spiked natural water samples were in the range of 91–96%. Finally, the method was applied to the separation/preconcentration and determination of trace lead in natural waters.

Segregation in Like-Charged Polyelectrolyte–Surfactant Mixtures Can Be Precisely Tuned via Manipulation of the Surfactant Mass Ratio

In this study, we consider segregative phase separation in aqueous mixtures of quaternary ammonium surfactants didecyldimethylammonium chloride (DDQ) and alkyl (C12, 70%; C14 30%) dimethyl benzyl ammonium chloride (BAC) upon the addition of poly(diallyldimethylammonium) chloride (pDADMAC) as a function of both concentration and molecular weight. The nature of the surfactant type is dominant in determining the concentration at which separation into an upper essentially surfactant-rich phase and lower polyelectrolyte-rich phase is observed. However, for high-molecular-weight pDADMAC there is a clear indication of an additional depletion flocculation effect. When the BAC/DDQ ratio is tuned, the segregative phase separation point can be precisely controlled. We propose a phase separation mechanism for like-charged quaternary ammonium polyelectrolyte/surfactant/water mixtures induced by a reduction in the ionic atmosphere around the surfactant headgroup and possible ion pair formation. An additional polyelectrolyte-induced depletion flocculation effect was also observed.

Simultaneous pre-concentration of Pb and Sn in food samples and determination by atomic absorption spectrometry

A cloud point extraction (CPE) method has been developed for the pre-concentration and simultaneous determination of lead [Pb(II)] and tin [Sn(II)] using Acridine Orange as complexing reagent and mediated by nonionic surfactant (Triton X-114) by flame atomic absorption spectrometry (FAAS). The main factors affecting analytical performance of CPE have been investigated in detail. The extracted surfactant-rich phase was diluted with (1.0 mol L−1) nitric acid in methanol, prior to subjecting FAAS. The calibration graphs obtained from Pb(II) and Sn(II) were linear in the concentration ranges of 5–1,000 and 10–5,000 μg L−1 with detection limits of 1.40 and 2.86 μg L−1, respectively. The relative standard deviations for 10 replicates containing 25 μg L−1 of Pb(II) and Sn(II) were 2.15 and 2.50 %, respectively. The analytical procedure was verified by the analysis of the standard reference materials NWTMDA-61.2 (water-trace elements) and NIST SRM 1548a (typical diet). The developed method has been applied to the simultaneous determination of total Pb and Sn in canned food samples including juices, tomato paste, corn, and green pea.

Cloud Point Extraction and Flame Atomic Absorption Spectrometric Determination of Cadmium and Nickel in Drinking and Wastewater Samples

A simple method for the preconcentration of cadmium (Cd) and nickel (Ni) in drinking and wastewater samples was developed. Cloud point extraction has been used for the preconcentration of both metals, after formation of complexes with 8-hydroxyquinoline (8-HQ) and extraction with the surfactant octylphenoxypolyethoxyethanol (Triton X-114). Dilution of the surfactant-rich phase with acidified ethanol was performed after phase separation, and the Cd and Ni contents were measured by flame atomic absorption spectrometry. The experimental variables, such as pH, amounts of reagents (8-HQ and Triton X-114), temperature, incubation time, and sample volume, were optimized. After optimization of the complexation and extraction conditions, enhancement factors of 80 and 61, with LOD values of 0.22 and 0.52 microg/L, were obtained for Cd and Ni, respectively. The proposed method was applied satisfactorily for the determination of both elements in drinking and wastewater samples.

The effect of temperature induced phase transitions in aqueous solutions of triblock copolymers and Triton X-100 on the EPR, magnetic relaxation and luminescent characteristics of Gd(III) and Eu(III) ions

The present report is inspired by the idea to develop novel spectroscopy based techniques to detect the phase transitions in solutions of triblock copolymers with the use of Gd(III) and Eu(III) ions as probes. The choice of (PEO)13(PPO)30(PEO)13 (L64), (PPO)14(PEO)24(PPO)14 (17R4), (PPO)8(PEO)22(PPO)8 (10R5) and Triton X-100 is conditioned by their phase transitions occurring in mild conditions. The cloud point extraction (CPE) data reveal the conditions (pH and chelating agent) where the binding of lanthanides with surfactant rich phase of triblock copolymers and Triton X-100 occurs. The effect of phase transitions in solutions of triblock copolymers on the temperature resolved line widths in EPR spectra of Gd(III) aqua ions and transverse relaxation rates of Gd(III) inner-sphere water protons depends on the architecture of triblock copolymers and pH conditions. The steady state luminescence of Eu(III) complexes with phosphine oxide in aqueous solutions of triblock copolymers and TX-100 is influenced by the temperature induced aggregation and phase separation in solutions of reverse triblock copolymers 17R4 and 10R5, while the effect of the aggregation is insignificant for L64.

Sensitive ergotamine determination in pharmaceuticals and biological samples using cloud point preconcentration and spectrofluorimetric detection

A new cloud point extraction (CPE) method for ergotamine analysis using fluorimetric detection is described. Ergotamine from an aqueous solution was preconcentrated into a smaller surfactant-rich phase using nonionic surfactant polyoxyethylene(7.5)nonylphenylether (PONPE 7.5). Differently from the conventional CPE procedure in which the resulting surfactant-rich phase is diluted by a fluidificant before its analysis, in this method the fluorescence measurements were carried out directly onto the undiluted surfactant-rich phase. The high viscosity provided by the undiluted surfactant rich phase greatly improved the fluorescence emission of ergotamine, leading to a total enhancement factor of 1325. This spectral advantage plus the preconcentration factor achieved, contributed to the method sensitivity allowing the ergotamine determination at trace level concentration. Under optimal experimental conditions, a linear calibration curve was obtained from 3.81×10−7 to 1.10μgmL−1, with detection and quantification limits of 0.11 and 0.38pgmL−1, respectively. The accuracy and versatility of the present methodology were proved by analyzing ergotamine in real samples of different natures such as pharmaceuticals, urine and saliva.

A Simple and Sensitive Approach for Determination of Iron Impurity in Military Grade Ammonium Perchlorate

In this work, we developed a simple and sensitive method for spectrophotometric determination of trace amounts of iron in ammonium perchlorate. The procedure is based on the reaction of Fe (II) with O-phenanthroline (O-Phen) to form colored complex ion, followed by extraction of the complex using cloud point extraction technique (CPE) in the presence of anionic surfactants sodium dodecyl sulfate (SDS) and nonionic surfactant Triton X-114 as mixed micelle- mediated. The complex concentrated in the surfactant rich phase was then determined at 510 nm. Some important parameters affecting reaction and extraction steps were investigated and optimized in details. Under the optimal conditions, the calibration graph for determination of iron was linear in the range of 25-700 ng mL -1 . Detection limit of the method was 10 ng mL -1 and the relative standard deviation (RSD) for five replicate determinations of iron at 200 ng mL -1

Selective cloud point extraction for the spectrophotometric determination of cetylpyridinium chloride in pharmaceutical formulations.

In this work, we developed a simple and selective method for separation and spectrophotometric determination of trace amounts of cetylpyridinium chloride (CPC) in pharmaceutical products using cloud point extraction (CPE) technique. The method is based on cloud point extraction of the CPC in alkali conditions using of nonionic surfactant Triton X-114. Under optimal conditions, the calibration graph was linear in the range of 0.50-30 μg/ mL of CPC with r=0.9993 (n=10). Average recoveries for spiked samples were determined to be between 95-104%. The relative standard deviation (RSD) for 5.0 μg/mL of CPC was 1.86 % (n=10). Also, the use of micellar extraction for extracting CPC was enhanced the molar absorptivity (ε) from 1.83×10(3) L/mol.cm in aqueous solution to 1.539×10(4) L/mol.cm in surfactant-rich phase. The proposed method was applied for the determination of CPC in a commercial mouth washer product.