A new cloud-point preconcentration approach for the spectrophotometric determination of p-aminophenol in the presence of paracetamol with 2-(2-Hydroxyphenyl)-1H-benzimidazole as a coupling reagent

A preconcentration and determination method for trace p-aminophenol (PAP) in paracetamol was developed. Cloud-point extraction (CPE) was employed for the preconcentration of p-aminophenol prior to spectrophotometric determination using Triton X-100 (TX-100) as an extractant. The determination is based on the reaction of p-aminophenol with 2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI) at room temperature in the presence of an oxidant to produce indophenol blue dye. The dye formed is subsequently entrapped in micelles of the surfactant TX-100. The surfactant-rich phase shows maximum absorbance at 650 nm and the proposed method is linear in the 0.1 to 5.0 mg mL⁻¹ concentration range. By preconcentrating 10 mL of the sample solution, a detection limit as low as 55 ng/mL was obtained after a single-step extraction and the experimental concentration factor achieved for this method was found to be 10. The stoichiometric composition of the dye is 1: 1 (PAP: HPBI). Some parameters such as HPBI, KIO₄, Na₂CO₃, and TX-100 concentration, extraction temperature, incubation, and centrifugation time, and the sample volume were investigated in detail. The established procedure was successfully adopted for the determination of p-aminophenol in the presence of paracetamol in various pharmaceutical preparations. The text was submitted by the authors in English.     

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 extraction and graphite furnace atomic absorption spectrometry determination of manganese(II) and iron(III) in water samples

Cloud point extraction (CPE) was applied as a preconcentration step prior to graphite furnace atomic absorption spectrometry (GFAAS) determination of manganese(II) and iron(III) in water samples. After complexation with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), the analytes could be quantitatively extracted to the phase rich in the surfactant p-octylpolyethyleneglycolphenylether (Triton X-100) and be concentrated, then determined by GFAAS. The parameters affecting the extraction efficiency, such as solution pH, concentration of PMBP and Triton X-100, equilibration temperature and time, were investigated in detail. Under the optimum conditions, preconcentration of 10 ml of sample solution permitted the detection of 0.02 ng ml(-1) of Mn(II) and 0.08 ng ml(-1) of Fe(III) with enrichment factors of 31 and 25 for Mn(II) and Fe(III), respectively. The proposed method was applied to determination of trace manganese(II) and iron(III) in water samples with satisfactory results.     

Determination of manganese in water samples by flame atomic absorption spectrometry after cloud point extraction

Cloud point extraction has been used for the preconcentration of manganese, after the formation of a complex with 1-(2-thiazolylazo)-2-naphthol (TAN), and later analysis by flame atomic absorption spectrometry using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The chemical variables affecting the separation phase and the viscosity affecting the detection process were optimized. Under the optimum conditions (i.e., pH = 9.2, [TAN] = 2.0 x 10(-5) mol l-1, [Triton X-114] = 0.05%, added methanol volume = 0.2 ml), preconcentration of 50 ml of sample solution permitted the detection of 0.28 ppb for manganese. The enhancement factor was 57.6. The proposed method has been applied to the determination of manganese in water samples.     

Cloud point and solid phase extraction of vanadium in surface and bottled mineral water samples using 8-hydroxyquinoline as a complexing reagent

Cloud point extraction (CPE) and solid phase extraction (SPE) methods were developed for the determination of ??g l^?1 of vanadium ions in surface, tap and bottled mineral water samples, based on the rapid reaction of vanadium(V) with 8- hydroxyquinoline (8-quinolinol) at pH 3?C5. Both the sensitive extraction methods were successfully employed for the preconcentration of V in real samples. For CPE, V complexed with 8-quinolinol and then was entrapped in non-ionic surfactant Triton X-114, while for SPE, V was adsorbed on XAD -2 impregnated with 8-quinolinol. The experimental conditions for SPE (pH, eluent, and contact time between the liquid sample and the resin) and CPE (pH of sample solution, concentration of 8- quinolinol and Triton X-114, equilibration temperature and time period for shaking) were investigated in detail. The validity of SPE/CPE of V was checked by certified reference material of water (SRM-1643e). The extracted surfactant-rich phase (200 ??l) was mixed with 200 ??l of HNO₃ in ethanol and this final volume was injected into electrothermal atomic absorption spectrometry with different modifiers. Under these conditions, the preconcentration of 25 ml sample solution allowed the raising of an enrichment factor of 100 and 10 folds for CPE and SPE, respectively. The concentration of V in surface water (river and lake), tap water and bottled mineral water samples was found to be in the range of 1.30?C19.9, 1.05?C5.25 and 0.67?C1.21 ??g l^?1, respectively.     

Design of rapidly synergistic cloud point extraction of ultra-trace lead combined with flame atomic absorption spectrometry determination

In this work, traditional cloud point extraction (CPE) pattern was changed and improved by the proposed rapidly synergistic CPE. Using octanol as cloud point revulsant and synergic reagent, non-ionic surfactant Triton X-114 (TX-114) accomplished room temperature extraction rapidly without heating in water bath. The improved extraction was named as rapidly synergistic cloud point extraction (RS-CPE). Compared with traditional CPE, RS-CPE was accomplished in 1 min with considerably high extraction efficiency. The improved CPE pattern was coupled with flame atomic absorption spectrometry (FAAS) for the extraction and detection of trace lead in real and certified water samples with satisfactory analytical results. The proposed method greatly improved the sensitivity of FAAS for the determination of lead. Under the optimal conditions, the limit of detection (LOD) for lead was 4.3 μg/L, with enhancement factor (EF) of 39. Factors influencing RS-CPE efficiency, such as concentrations of surfactant TX-114 and octanol, concentration of chelating agent, pH, conditions of phase separation, environmental temperature, salt effect and instrumental conditions, were studied systematically.     

Cloud point extraction–thermospray flame quartz furnace atomic absorption spectrometry for determination of ultratrace cadmium in water and urine

A simple, low cost and highly sensitive method based on cloud point extraction (CPE) for separation/preconcentration and thermospray flame quartz furnace atomic absorption spectrometry was proposed for the determination of ultratrace cadmium in water and urine samples. The analytical procedure involved the formation of analyte-entrapped surfactant micelles by mixing the analyte solution with an ammonium pyrrolidinedithiocarbamate (APDC) solution and a Triton X-114 solution. When the temperature of the system was higher than the cloud point of Triton X-114, the complex of cadmium-PDC entered the surfactant-rich phase and thus separation of the analyte from the matrix was achieved. Under optimal chemical and instrumental conditions, the limit of detection was 0.04 μg/L for cadmium with a sample volume of 10 mL. The analytical results of cadmium in water and urine samples agreed well with those by ICP-MS.     

Investigation of analytical performance for rapidly synergistic cloud point extraction of trace amounts of copper combined with spectrophotometric determination

In this work, an improved preconcentration method named as rapidly synergistic cloud point extraction (RS-CPE) was established for copper preconcentration and determination. Non-ionic surfactant Triton X-100 (TX-100) was used as extractant. Octanol worked as cloud point revulsant and synergic reagent, which successfully decreased the cloud point temperature (CPT) of TX-100 to realize the room temperature (about 20°C) CPE without heating. The established RS-CPE pretreatment was simple, rapid and effective. Compared with traditional CPE (about 40 min for heating, incubation and cooling), the extraction time of the proposed method was very short (1 min). The improved extraction technique RS-CPE was combined with traditional spectrophotometer to improve the analytical performance and expand the application of spectrophotometric determination. The influence factors relevant to RS-CPE, such as concentrations of TX-100 and octanol, concentration of chelating agent, pH, conditions of phase separation, salt effect, environmental temperature and instrumental conditions, were studied in detail. Under the optimal conditions, the limit of detection (LOD) for copper was 0.4 μg L(-1), with sensitivity enhancement factor (EF) of 18. The proposed method was applied to the determination of trace copper in real samples and certified samples with satisfactory analytical results.     

Cloud point extraction and preconcentration for the gas chromatography of phenothiazine tranquilizers in spiked human serum.

Cloud point extraction was successfully applied to the preconcentration of phenothiazine derivatives, such as pericyazine (PC), chlorpromazine (CP) and fluphenazine (FUL), for gas chromatography (GC). Phenothiazine derivatives were separated from surfactants by passing the surfactant-rich phase through a cation exchange column after cloud point extraction, permitting the determination of the phenothiazine derivatives extracted in the surfactant-rich phase by GC. The optimal condition for the cloud point extraction of phenothiazine derivatives was also investigated using Triton X-100, Triton X-114, and PONPE10. Triton X-114 provided the most efficient recovery of phenothiazine derivatives among the surfactants used. The addition of sodium chloride and excess ammonia to the sample solution resulted in a decrement of the recovery of the phenothiazine derivatives. The proposed method was applied to the determination of phenothiazine derivatives in spiked human serum by GC. The recoveries of PC, CP, and FUL in spiked human serum were 95.1%, 87.1%, and 84.7%, respectively.     

Prediction of the behaviour of organic pollutants using cloud point extraction

A preconcentration study based on the cloud point phenomenon was carried out for a set of triazine herbicides, three of them chloro-substituted and three of them methylthio-substituted. Concentration factors and recoveries were calculated as function of the percentage of the non-ionic surfactant Triton X-114 employed. From these values, obtained from a cloud point extraction (CPE) procedure, the distribution coefficient between the Triton X-114 micelles and water, Kc, prior to CPE was calculated for each triazine and related to the corresponding octanol-water partition coefficient, Kow. In order to confirm the results obtained with the triazine herbicides, two sets of data from chemically different organic pollutants--organophosporous and chlorophenols--obtained from the literature were assessed, concluding that they display a similar behaviour to that of the triazine herbicides. This can be used to predict the CPE behaviour of other organic pollutants from their octanol-water partition coefficients. The Kc values were compared with the analyte concentration ratio in the surfactant-rich phase and aqueous phase (Ksa) with a view to obtaining a link between the analyte behaviour prior to and after cloud point extraction procedures.     

Fiber optic-linear array detection spectrophotometry in combination with cloud point extraction for simultaneous preconcentration and determination of cobalt and nickel

A new combined method including fiber optic-linear array detection spectrophotometry (FO-LADS) and cloud point extraction (CPE) was developed using a cylindrical micro cell for simultaneous preconcentration and determination of different species. The CPE and FO-LADS methods have good matching conditions for combination because FO-LADS is suitable as a detection technique for the low volume of remained phase obtained after CPE. This combination was carried out using 50 μL cylindrical micro cell and then employed for simultaneous preconcentration and determination of cobalt and nickel.Cloud point extraction method was based on the chromogenic reaction of metal ions and 1-(2-pyridylazo)-2-naphthol (PAN) and then preconcentration of formed complexes using octylphenoxypolyethoxyethanol (Triton X-114). The remained phase after CPE was transferred into cylindrical micro cell and located at the cell holder of FO-LADS. The spectra of cobalt and nickel complexes were collected by FO-LADS and processed for ordinary and first derivative spectrophotometry.Optimization of different parameters was evaluated. Under optimum conditions, calibration curves were linear in the range of 0.6-30.0 and 0.1-15.0 μg L⁻¹ with detection limits of 0.2 and 0.04 μg L⁻¹ for Co and Ni respectively. The relative standard deviations (R.S.D.s) were lower than 4%. The obtained enhancement factors were 198 and 199 for cobalt and nickel, respectively.The proposed method was compared with the other methods and applied to the analysis of several real and spiked samples.     

Cloud point preconcentration and flame atomic absorption spectrometric determination of Cd and Pb in human hair

Cloud point methodology has been successfully used for the preconcentration of trace amounts of Cd and Pb as a prior step to their determination by flame atomic absorption spectrometry. O,O-Diethyldithiophosphate and Triton X-114 are used as hydrophobic ligand and non-ionic surfactant, respectively. After phase separation at 40 °C based on cloud point of the mixture, the surfactant-rich phase is diluted with methanol. The enriched analyte in the final solution is determined by flame atomic absorption spectrometry using conventional nebulization. After optimization of the complexation and extraction conditions, enhancement factors of 22 and 43 were obtained for Cd and Pb, respectively. Under the experimental conditions used, preconcentration of only 10 ml of sample in the presence of 0.05% (v/v) Triton X-114 permitted the detection of 0.62 μg l⁻¹ of Cd and 2.86 μg l⁻¹of Pb. The proposed method was applied to the determination of Cd and Pb in human hair samples.     

Cloud point extraction of trace metals from seawater and determination by electrothermal atomic absorption spectrometry with iridium permanent modifier.

A simple method is described for preconcentration and separation of trace metals such as Ag, Co, Cr, Cu, Fe, Mn, Ni and Pb simultaneously from seawater using a cloud point extraction (CPE) procedure. Triton X-114 nonionic surfactant and ammonium pyrrolidine dithiocarbamate (APDC) have been used as an extraction medium and a chelating extractant, respectively. The amounts of Triton X-114 and APDC and the pH value necessary for extraction were carefully optimized. The preconcentration factor of about 200 is achieved for all the studied metals. Electrothermal atomic absorption spectrometry (ETAAS) with an Ir coated graphite tube as permanent chemical modifier has been used for determination. The limits of detection of Ag, Co, Cr, Cu, Fe, Mn, Ni and Pb were 0.003, 0.008, 0.003, 0.006, 0.015, 0.002, 0.009 and 0.01 ng ml-1, respectively. Certified reference materials such as CASS-4 and NASS-5 (seawater) and NIST-1640 (natural water) have been used for validation of the new method. The relative standard deviation (%) obtained for all the metals are in the range 0.8 - 3.6% for natural water and 11-25% for seawater materials, except for Co in NASS-5 for which it was 50%.     

Cloud point extraction for the determination of lead and cadmium in urine by graphite furnace atomic absorption spectrometry with multivariate optimization using Box–Behnken design

Cloud point extraction (CPE) is proposed as a pre-concentration procedure for the determination of Pb and Cd in undigested urine by graphite furnace atomic absorption spectrometry (GF AAS). Aliquots of 0.5 mL urine were acidified with HCl and the chelating agent ammonium O,O-diethyl dithiophosphate (DDTP) was added along with the non-ionic surfactant Triton X-114 at the optimized concentrations. Phase separation was achieved by heating the mixture to 50 °C for 15 min. The surfactant-rich phase was analyzed by GF AAS, employing the optimized pyrolysis temperatures of 900 °C for Pb and 800 °C for Cd, using a graphite tube with a platform treated with 500 μg Ru as permanent modifier. The reagent concentrations for CPE (HCl, DDTP and Triton X-114) were optimized using a Box–Behnken design. The response surfaces and the optimum values were very similar for aqueous solutions and for the urine samples, demonstrating that aqueous standards submitted to CPE could be used for calibration. Detection limits of 40 and 2 ng L^− 1 for Pb and Cd, respectively, were obtained along with an enhancement factor of 16 for both analytes. Three control urine samples were analyzed using this approach, and good agreement was obtained at a 95% statistical confidence level between the certified and determined values. Five real samples have also been analyzed before and after spiking with Pb and Cd, resulting in recoveries ranging from 97 to 118%.     

Speciation analysis of manganese in tea samples using flame atomic absorption spectrometry after cloud point extraction

The speciation of Mn(II) in tea infusion was studied using cloud point extraction (CPE). In tea infusion, the flavonoid-bound Mn(II) was extracted at pH 5.0 using Triton X-100 (TX-100), the remaining free aquated Mn(II) and weakly-complexed Mn(II) in solution were both chelated with 8-hydroxyquinoline (HOx) and CPE-preconcentrated with TX-100. The enriched analyte was determined by flame AAS. The optimal concentrations for CPE of 0.02 ppm Mn were as follows: TX-100, 0.2% (v/v); HOx, 1.0 × 10⁻⁴ M; NaCl, 1.0% (w/v). LOD was 1.9 μg/L with a preconcentration factor of 10–20. The method was validated using a standard XAD-resin separation procedure and applied to synthetic seawater and CRM samples.     

Cloud point extraction, preconcentration and simultaneous spectrophotometric determination of nickel and cobalt in water samples

Cloud point extraction has been used for the preconcentration and simultaneous spectrophotometric determination of nickel and cobalt after the formation of a complex with 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA), and latter analysis by spectrophotometer using Triton X-114 as surfactant. The parameters affecting the separation phase and detection process were optimized. Under the optimum experimental conditions (i.e. pH=5, 0.07 mM ACDA, Triton X-114=0.25% (w/v)), calibration graphs were linear in the range of 20-500 and 20-200 microg l(-1) with detection limits of 10 and 7.5 microg l(-1) for Ni and Co, respectively. The method was applied to the determination of Ni and Co in natural and waste water samples with satisfactory results.     

Determination of trace vanadium in sea cucumbers by ultrasound-assisted cloud point extraction and graphite furnace atomic absorption spectrometry

An ultrasound-assisted cloud point extraction (CPE) procedure was used for preconcentration and determination of vanadium by graphite furnace atomic absorption spectrometry. The vanadyl(IV) complex with ascorbic acid form a hydrophobic complex with 4-(2-pyridylazo) resorcinol (PAR) in a micelle medium, which is stable under our working conditions, and followed by its extraction into Triton X-100 surfactant-rich phase. The main factors affecting CPE efficiency, such as pH, concentrations of PAR, ascorbic acid and Triton X-100, incubation temperature, frequency and equilibration time of ultrasonic bath were investigated in detail. Under the optimum conditions, preconcentration of 10 mL sample gave a preconcentration factor of 36.4 and a detection limit of 4.0 µg kg^?1. The proposed method was successfully applied to determination of vanadium in sea cucumbers with satisfactory results.     

Determination of arsenic in scalp hair samples from exposed subjects using microwave-assisted digestion with and without enrichment based on cloud point extraction by electrothermal atomic absorption spectrometry

A simple and rapid cloud point extraction (CPE) procedure was applied for preconcentration of trace quantities of arsenic (As) in scalp hair samples. The samples were subjected to microwave-assisted digestion in a mixture of nitric acid and hydrogen peroxide (2 + 1, v/v) prior to preconcentration by CPE. The As in digested samples was complexed with ammonium pyrrolidine dithiocarbamate (APDC), and the resultant As-PDC complex was extracted by a nonionic surfactant, octylphenoxypolyethoxyethanol (Triton X-114). After centrifugation, the surfactant-rich phase was diluted with 0.1 M HNO3 in methanol and analyzed by electrothermal atomic absorption spectrometry. The experimental parameters, i.e., amount of APDC, concentration of Triton X-114, equilibrium temperature and time, were optimized. For validation of the proposed method, a certified reference material (CRM) of human hair (BCR 397) was used. No significant difference (P > 0.05) was observed between the experimental results and certified values of the CRM (paired t-test). The LOD and LOQ obtained under the optimal conditions were 0.025 and 0.083 microg/kg, respectively. The developed method was applied for the determination of As in scalp hair samples from male and female subjects of two villages of Khairpur Mir's, Pakistan.     

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 50 mL solution. Under the optimal conditions, the detection limit of this method for Al(III) is 1.43 μg L^− 1, and the relative standard deviation is 2.7% at determination of 100 μg L^− 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 ultra trace arsenic species in water samples by hydride generation atomic absorption spectrometry after cloud point extraction

Cloud point extraction (CPE) methodology has successfully been employed for the preconcentration of ultra-trace arsenic species in aqueous samples prior to hydride generation atomic absorption spectrometry (HGAAS). As(III) has formed an ion-pairing complex with Pyronine B in presence of sodium dodecyl sulfate (SDS) at pH 10.0 and extracted into the non-ionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-114). After phase separation, the surfactant-rich phase was diluted with 2 mL of 1 M HCl and 0.5 mL of 3.0% (w/v) Antifoam A. Under the optimized conditions, a preconcentration factor of 60 and a detection limit of 0.008 μg L⁻¹ with a correlation coefficient of 0.9918 was obtained with a calibration curve in the range of 0.03–4.00 μg L⁻¹. The proposed preconcentration procedure was successfully applied to the determination of As(III) ions in certified standard water samples (TMDA-53.3 and NIST 1643e, a low level fortified standard for trace elements) and some real samples including natural drinking water and tap water samples.