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.     

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.     

Spectrophotometric determination of paracetamol in urine with tetrahydroxycalix[4]arene as a coupling reagent and preconcentration with triton X-114 using cloud point extraction

In the present paper, conventional spectrophotometry in conjunction with cloud point extraction-preconcentration were investigated as alternative methods for paracetamol (PCT) assay in urine samples. Cloud point extraction (CPE) was employed for the preconcentration of p-aminophenol (PAP) prior to spectrophotometric determination using the non-ionic surfactant Triton X-114 (TX-114) as an extractant. The developed methods were based on acidic hydrolysis of PCT to PAP, which reacted at room temperature with 25,26,27,28-tetrahydroxycalix[4]arene (CAL4) in the presence of an oxidant (KIO(4)) to form an blue colored product. The PAP-CAL4 blue dye formed was subsequently entrapped in the surfactant micelles of Triton X-114. Cloud point phase separation with the aid of Triton X-114 induced by addition of Na(2)SO(4) solution was performed at room temperature as an advantage over other CPE assays requiring elevated temperatures. The 580 nm-absorbance maximum of the formed product was shifted bathochromically to 590 nm with CPE. The working range of 1.5-12 mug ml(-1) achieved by conventional spectrophotometry was reduced down to 0.14-1.5 mug ml(-1) with cloud point extraction, which was lower than those of most literature flow-through assays that also suffer from nonspecific absorption in the UV region. By preconcentrating 10 ml sample solution, a detection limit as low as 40.0 ng ml(-1) was obtained after a single-step extraction, achieving a preconcentration factor of 10. The stoichiometric composition of the dye was found to be 1 : 4 (PAP : CAL4). The impact of a number of parameters such as concentrations of CAL4, KIO(4), Triton X-100 (TX-100), and TX-114, extraction temperature, time periods for incubation and centrifugation, and sample volume were investigated in detail. The determination of PAP in the presence of paracetamol in micellar systems under these conditions is limited. The established procedures were successfully adopted for the determination of PCT in urine samples. Since the drug is rapidly absorbed and excreted largely in urine and its high doses have been associated with lethal hepatic necrosis and renal failure, development of a rapid, sensitive and selective assay of PCT is of vital importance for fast urinary screening and antidote administration before applying more sophisticated, but costly and laborious hyphenated instrumental techniques of HPLC-SPE-NMR-MS.     

Cloud point extraction and preconcentration of gold in geological matrices prior to flame atomic absorption determination

Brilliant green was used as a complexing agent in cloud point extraction (CPE) and applied for selective preconcentration of trace amounts of gold in geological matrices. The analyte in the initial aqueous solution was acidified with hydrochloric acid (0.1 M) and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant. After phase separation, based on the cloud point separation of the mixture, the surfactant rich phase was diluted with methanol and the analyte determined in the surfactant rich phase by flame atomic absorption spectrometry (FAAS). After optimization of the complexation and extraction conditions, a preconcentration factor of 31 was obtained for only 10 mL of sample. The analytical curve was linear in the range of 3–1000 ng mL⁻¹ and the limit of detection was 1.5 ng mL⁻¹. The proposed method was applied to the determination of gold in geological samples.     

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 of aloe anthraquinones based on non-ionic surfactant aqueous two-phase system

Non-ionic surfactant-based aqueous two-phase system had been investigated to extract aloe anthraquinones. It had the advantage of using a single auxiliary chemical to induce phase separation above cloud point at a low concentration. Non-ionic surfactant Triton X-114 was chosen for its excellent phase-separating ability and low cloud point. The main factors affecting the cloud point extraction were discussed such as equilibrium temperature and time, concentrations of surfactant and inorganic electrolytes, pH, etc. Under the optimised conditions, the highest extraction yield 96.93% was obtained. The reverse extraction of anthraquinones from surfactant-rich phase was achieved with a recovery of 70.35% by adjusting pH. Compared with conventional purification methods, this CPE technique can be completed in one operation; besides, it is a low-cost method and an environment friendly one.     

Determination of cadmium in rice and water by tungsten coil electrothermal vaporization-atomic fluorescence spectrometry and tungsten coil electrothermal atomic absorption spectrometry after cloud point extraction

In this work, the microsampling nature of tungsten coil electrothermal vaporization Ar/H₂ flame atomic fluorescence spectrometry (W-coil ETV-AFS) as well as tungsten coil electrothermal atomic absorption spectrometry (W-coil ET-AAS) was used with cloud point extraction (CPE) for the ultrasensitive determination of cadmium in rice and water samples. When the temperature of the extraction system is higher than the cloud point temperature of the selected surfactant Triton X-114, the complex of cadmium with dithizone can be quantitatively extracted into the surfactant-rich phase and subsequently separated from the bulk aqueous phase by centrifugation. The main factors affecting the CPE, such as concentration of Triton X-114 and dithizone, pH, equilibration temperature and incubation time, were optimized for the best extract efficiency. Under the optimal conditions, the limits of detection for cadmium by W-coil ETV-AFS and W-coil ET-AAS were 0.01 and 0.03 μg L⁻¹, with sensitivity enhancement factors of 152 and 93, respectively. The proposed methods were applied to the determination of cadmium in certified reference rice and water samples with analytical results in good agreement with certified values.     

Equilibrium partition of polycyclic aromatic hydrocarbons in cloud point extraction with a silicone surfactant

In the cloud point extraction (CPE) process with PEG/PPG-18/18 dimethicone, the flexible chain structure of the silicone surfactant efficiently decreased the water content remaining in the surfactant-rich phase, compared with conventional nonionic surfactants, represented by Triton X-114. Meanwhile, the phase volume ratio of surfactant-rich phase to aqueous phase obtained in the silicone surfactant CPE system was found to be maintained at a low value with increasing surfactant concentration; whereas a rapid increase tendency was commonly observed in that of other nonionic surfactants. Based on these advantages, the equilibrium partition of three polycyclic aromatic hydrocarbons (PAHs), anthracene, phenanthrene and pyrene, was studied in the CPE process with PEG/PPG-18/18 dimethicone. Equilibrium parameters, including preconcentration factor, distribution coefficient and recovery, were determined, and the performance was compared with that of another related CPE research, where Tergitol 15-S-7 was used. Due to the low surfactant-rich phase volume, higher concentrations of the three PAHs in the surfactant-rich phase, and the resulting higher preconcentration factors and distribution coefficients were able to be achieved at the same time. Moreover, the great performance was able to be maintained even at a high surfactant concentration or PAHs initial concentration.     

Laser induced thermal lens spectrometry for cobalt determination after cloud point extraction

A new approach, employing cloud point extraction (CPE) in combination with thermal lens spectrometry (TLS), has been developed for the determination of cobalt. The CPE and TLS methods have good matching conditions for combination because TLS is suitable for low volume samples obtained after CPE and for organic solvents, which are used for dissolving the remaining analyte phase.1-(2-Pyridylazo)-2-naphthol (PAN) was used as a complexing agent and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant; then the pH of solution was adjusted. After phase separation at 50 °C based on the cloud point extraction of the mixture, the surfactant-rich phase was dried and the remaining phase was dissolved using 20 μL of carbon tetrachloride. The obtained solution was introduced into the quartz micro cell and the analyte was determined by thermal lens spectrometry. The He-Ne laser (632.8 nm) was used as both the probe and the excite source.Under optimum conditions, the analytical curve was linear for the concentration range of 0.2-40 ng mL⁻¹ and the detection limit was 0.03 ng mL⁻¹. The enhancement factor of 470 was achieved for a 10 mL sample. Relative standard deviations were lower than 5%.The method was successfully applied to the extraction and determination of cobalt in tap, river and sea water.     

浊点萃取-分光光度法测定自来水及酒类样品中的痕量铁

利用非离子表面活性剂TritonX-100在温度高于其浊点时形成相分离行为,建立了浊点萃取-分光光度法测定痕量铁的新方法,探讨优化了以KSCN为显色剂,TritonX-100浊点萃取富集痕量铁的实验条件.研究发现:加入正辛醇可使TritonX-100的浊点降低约30℃,有利于萃取实验的进行;同时,加入的正辛醇与TritonX-100对痕量铁起到了协同萃取作用.在优化了的实验条件下,进行了痕量铁的分析,检出限为0.02mg·L-1,加标回收率为97.4%～101.6%,应用于自来水及酒类样品中痕量铁的测定,结果满意.     

Cloud point extraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the speciation of inorganic selenium in environmental water samples

A new method based on cloud point extraction (CPE) separation and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICPMS) detection has been proposed for the speciation of inorganic selenium in environmental waters. When the temperature of the system is higher than the cloud point temperature (CPT) of the selected surfactant Triton X-114, the complex of Se(IV) with ammonium pyrrolidine dithiocarbamate (APDC) seems to be extracted into the surfactant-rich phase, whereas the Se(VI) remains in aqueous solutions. Thus, an in situ separation of Se(IV) and Se(VI) could be realized. The concentrated analyte was introduced into the ETV-ICP mass spectrometer for determination of Se((IV) after dilution with 200 microL methanol. Se(VI) was reduced to Se(IV) prior to determining total selenium, and its assay was based on subtracting Se(IV) from total selenium. The main factors affecting the CPE and the vaporization behavior of the analyte were investigated in detail. Under the optimized experimental conditions, the limit of detection (LOD) for Se(IV) was 8.0 ng/L with an enhancement factor of 39 when 10 mL of sample solution was preconcentrated to 0.2 mL. The relative standard deviation (RSD) was found to be 3.9% (C(Se(IV)) = 1.0 microg/L, n = 7). The proposed method was applied to the speciation of inorganic selenium in different environmental water samples with the recovery for the spiked samples in the range of 82-102%.     

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.     

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.     

Micro-cloud point extraction for preconcentration of Aspirin in commercial tablets prior to spectrophotometric determination

A fast, simple, inexpensive and effective method is developed for spectrophotometric determination of Aspirin in commercial tablets based on micro-cloud point extraction (MCPE). The proposed MCPE is essentially a miniaturized form of traditional cloud point extraction (CPE) in which only a few microliters of micellar extracting phase is sufficient for spectrophotometric determination. For comparison with MCPE, cloud point extraction was examined for Aspirin extraction. Triton X-114 was employed as a non-ionic surfactant for extraction/preconcentration of aspirin. Factors influencing the extraction efficiency, such as concentration of Triton, effect of pH, type of dilution solvent, etc. were investigated and optimized. Under the optimized condition, linear calibration curve for MCPE was in the range of 0.05–2 mg/L and limit of detection of 0.05 mg/L was obtained, whereas linear part for CPE calibration curve was 0.9 to 11 mg/L with a limit of detection of 0.5 mg/L.     

Simultaneous spectrophotometric determination of uranium and zirconium using cloud point extraction and multivariate methods

A cloud point extraction (CPE) process using the nonionic surfactant Triton X-114 to simultaneous extraction and spectrophotometric determination of uranium and zirconium from aqueous solution using partial least squares (PLS) regression is investigated. The method is based on the complexation reaction of these cations with Alizarin Red S (ARS) and subsequent micelle-mediated extraction of products. The chemical parameters affecting the separation phase and detection process were studied and optimized. Under the optimum experimental conditions (i.e. pH 5.2, Triton X-114?=?0.20%, equilibrium time 10?min and cloud point 45?°C), calibration graphs were linear in the range of 0.01?C3?mg?L^?1 with detection limits of 2.0 and 0.80???g L^?1 for U and Zr, respectively. The experimental calibration set was composed of 16 sample solutions using an orthogonal design for two component mixtures. The root mean square error of predictions (RMSEPs) for U and Zr were 0.0907 and 0.1117, respectively. The interference effect of some anions and cations was also tested. The method was applied to the simultaneous determination of U and Zr in water samples.     

Laser induced-thermal lens spectrometry after cloud point extraction for the determination of trace amounts of rhodium

A new combination method, employing thermal lens spectrometry (TLS) after cloud point extraction (CPE), has been developed for the preconcentration and determination of rhodium. TLS and CPE methods have good matching conditions for the combination because TLS is a suitable method for the analysis of low volume samples obtained after CPE.Rhodium was complexed with 1-(2-pyridylazo)-2-naphthol (PAN) as a complexing agent in an aqueous medium and concentrated by octylphenoxypolyethoxyethanol (Triton X-114) as a surfactant. After the phase separation at 50 °C based on the cloud point extraction of the mixture, the surfactant-rich phase was dried and the remaining phase was dissolved using 20 μL of carbon tetrachloride. The obtained solution was introduced into a quartz micro cell and the analyte was determined by laser induced-thermal lens spectrometry (LI-TLS). The single laser TLS was used as a sensitive method for the determination of Rhodium-PAN complex in 20 μL of the sample. Under optimum conditions, the analytical curve was linear for the concentration range of 0.5-50 ng mL⁻¹ and the detection limit was 0.06 ng mL⁻¹. The enhancement factor of 450 was achieved for 10 mL samples containing the analyte and relative standard deviations were lower than 5%. The developed method was successfully applied to the extraction and determination of rhodium in water samples.     

Evaluation of a cloud point extraction method for the preconcentration and quantification of silver nanoparticles in water samples by ETAAS

ABSTRACT

A simple and reliable analytical method using instrumentation available in most of the laboratories has been developed for the separation and determination of silver nanoparticles in water samples. Cloud point extraction (CPE) was used for the separation of silver nanoparticles (AgNPs) from the sample and these nanoparticles were then determined by electrothermal atomic absorption spectrometry (ETAAS). Parameters related to the cloud point extraction procedure (Triton X-114 concentration, type of complexing agent (EDTA or Na₂S₂O₃), pH, incubation temperature, incubation and centrifugation time) were selected using a multivariate approach (designs of experiments); 8.6% (v/v) Triton X-114, 750 µL saturated EDTA and pH 7 were selected as the optimum conditions. Calibration standards in a concentration range from 0 to 10 µg L^?1 of AgNPs were subjected to the CPE procedure to obtain quantitative recoveries. The LOD and LOQ were 0.04 and 0.13 µg L^?1, respectively. The method is selective for the extraction of AgNPs, and ionic Ag remains in the aqueous phase. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was used to evaluate the effect of the CPE procedure in particle size, and no changes were observed. Finally, the procedure was applied to wastewater samples spiked with nanoparticles with quantitative recoveries.     

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.     

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.     

Taguchi OA16 orthogonal array design for the optimization of cloud point extraction for selenium determination in environmental and biological samples by tungsten-modified tube electrothermal atomic absorption spectrometry

Orthogonal array design (OAD) was applied for the first time to optimize cloud point extraction (CPE) conditions for Se(IV) determination by electrothermal atomic absorption spectrometry (ETAAS) in environmental and biological samples. Selenium was reacted with o-phenylenediamine to form piazselenol in an acidic medium (pH 2). Using Triton X-114, as surfactant, piazselenol was quantitatively extracted into small volume (about 30 μL) of the surfactant-rich phase after centrifugation. Five relevant factors, i.e. surfactant concentration, pH, ionic strength, equilibrium time and temperature were selected and the effects of each factor were studied at four levels on the extraction efficiency of Se(IV) and optimized. The statistical analysis revealed that the most important factors contributing to the extraction efficiency are ionic strength, pH and percent of surfactant. Based on the results obtained from the analysis of variance (ANOVA), the optimum conditions for extraction were established as: pH 6; vial temperature = 50 °C; extraction time = 7 min and 0.3% (w/v) of Triton X-114. The method was permitted to obtain a detection limit of 0.09 ng mL⁻¹ and two linear calibration ranges from 0.6 to 1.0 and 1.0 to 80.0 ng mL⁻¹ Se. The precision (%RSD) of the extraction and determination for the six replicates of Se at 20 ng mL⁻¹ was better than 3.6% and the enrichment factor of 63.5 was achieved. The studied analyte was successfully extracted and determined with high efficiency using cloud point extraction method in water and biological matrices.