Separation and preconcentration by cloud point extraction procedures for determination of ions: recent trends and applications

The cloud point extraction procedure is an alternative to liquid–liquid extraction and based on the phase separation that occurs in aqueous solutions of non-ionic surfactants when heated above the so-called cloud point temperature. We review the more recent applications for determination of ions by means of this procedure for sample preparation over the range 2009 to first part of 2011. Following an introduction, the article covers aspects of cloud point extraction of one metal ion, two metals ions simultaneously, three metal ions simultaneously, multielement analysis, anions analysis, and on-line cloud point extraction. One hundred sixteen references are cited.

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.     

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 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.     

浊点萃取技术在金属离子分离和富集以及形态分析中应用的进展

介绍了新兴的环保型液液萃取方法——浊点萃取的原理及操作方法，讨论了影响浊点萃取效率的因素，重点回顾了近年来该技术在金属离子分离和富集以及形态分析中应用的进展，探讨了该技术的发展前景。     

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.     

Separation and preconcentration of persistent organic pollutants by cloud point extraction

Persistent organic pollutants (POPs) are recognized as a class of poisonous compounds which pose risks of causing adverse effects to human health and the environment. Thus, it is very important to detect POPs in environmental and biological samples. The identification and determination of very low levels of POPs in complex matrices is extremely difficult. Recently a promising environmentally benign extraction and preconcentration methodology based on cloud point extraction (CPE) has emerged as an efficient sample pretreatment technique for the determination of trace/ultra-trace POPs in complex matrices. The purpose of this paper is to review the past and latest use of CPE for preconcentrating POPs and its coupling to different contemporary instrumental methods of analysis. First, the comparison of various extraction techniques for POPs is described. Next, the general concept, influence factors and other methods associated with CPE technique are outlined and described. Last, the hyphenations of CPE to various instrumental methods for their determination are summarized and discussed.     

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.     

浊点萃取-高效液相色谱法同时测定药片与尿样中异烟肼、利福平和吡嗪酰胺

建立了以聚乙二醇(PEG)6000为萃取剂的浊点萃取(CPE)-反相高效液相色谱同时测定异烟肼、利福平和吡嗪酰胺的方法,由于异烟肼不易被浊点萃取方法富集,使异烟肼与对氯苯甲醛在酸性条件下反应衍生为异烟肼腙,异烟肼腙在液相色谱上的信号与异烟肼浓度存在着线性关系.在优化的CPE条件下,采用梯度洗脱的方式,用紫外检测器在310 nm波长下,异烟肼、吡嗪酰胺和利福平的保留时间分别为14.5、34.4和38.1 min,定量范围分别是0.01～10 mg/L、0.08～25 mg/L和0.05～20 mg/L.线性相关系数r>0.99.3种药的平均回收率范围为91.50%～98.75%,精密度(RSD)为 0.22%～1.54%.异烟肼、利福平和吡嗪酰胺的检出限分别为4×10-3、2×10-2和3×10-2 mg/L.本法用于药片和尿样中3种药物的检测,结果满意.     

Cloud point extraction preconcentration of manganese(II) from natural water samples using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and triton X-100 and determination by flame atomic absorption spectrometry.

The possibility was investigated by using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) as the chelating reagent for separation and preconcentration of manganese(II) by cloud point extraction (CPE) and subsequent determination by flame atomic absorption spectrometry (FAAS). The effects of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction were studied. Under the optimum conditions, preconcentration of 10 ml of sample solution permitted the detection of 1.45 ng mL(-1) of manganese with an enrichment factor of 20. The proposed method was applied to the determination of trace manganese in water samples with satisfactory results.     

Cloud Point Extraction of Serum Albumin and Its Spectrophotometric Determination in Serum Samples

Abstract

A new method based on the cloud point extraction (CPE) separation and ultraviolet spectrometry determination was proposed for the determination of albumin. When the system temperature is higher than the cloud point extraction temperature (CPT) of the mixed surfactant of p‐octyl polyethyleneglycolphenyether (Triton X‐100) and sodium dodecyl sulfate (SDS), serum albumin could be extracted into surfactant‐rich phase. The main factors affecting the cloud point extraction were investigated systematically. Under the optimized conditions, the determination limit for serum albumin as low as 0.18 µg/mL was obtained by preconcentrating a 10 mL sample solution, and the relative standard deviation (n=10, c=40.0 µg/mL) was 3.77%. The proposed method was applied to the determination of albumin in serum samples. The results obtained by this method were in good agreement with coomassie brilliant blue (CBB).     

浊点萃取-热喷雾火焰炉原子吸收光谱法测定水中痕量锌(Ⅱ)

建立了以吡咯烷二硫代氨基甲酸铵(APDC)为络合剂、TritonX-100为表面活性剂的浊点萃取-热喷雾火焰原子吸收光谱法测定水样中痕量锌的方法.考查了APDC的浓度、溶液酸度、表面活性剂浓度、加热时间、水浴温度、干扰离子等实验条件对浊点萃取效率的影响.在最优化的实验条件下.方法的检出限为0.1 ng/mL,RsD为4...     

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.     

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.     

Electromagnetic induction-assisted heating as a new method for on-line cloud point extraction of cadmium from water samples

We report on a novel method for on-line cloud point extraction (CPE) for preconcentration of cadmium ions. It is based on electromagnetic induction-assisted heating (EMIH) of iron particles in a packed bed contained in a quartz tube that acts as an on-line CPE enrichment column. The cadmium complex of 1-(2-pyridylazo)-2-naphthol is quantitatively retained by the column under the cloud point temperature with the help of EMIH. The column was then eluted with alcoholic borax buffer at room temperature and on-line coupled to FAAS. Under optimum conditions, the limit of detection (3 s_b/b) and limit of quantification (10 s_b/b) are 0.21 μg?L^?1 and 0.70 μg?L^?1 of Cd(II), respectively, and the relative standard deviation is 3.8 % (for n?=?8; at 20 ng?mL^?1). An enhancement factor of 76 is typically achieved. The correlation coefficient of the calibration graph using the present method was 0.9986. The method was successfully applied to determine Cd(II) in water samples

Cloud Point Extraction Preconcentration of Trace Cadmium as 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone Complex and Determination by Flame Atomic Absorption Spectrometry

A new method for the determination of trace cadmium in water samples by flame atomic absorption spectrometry (FAAS) after cloud point extraction (CPE) is proposed. The method is based on the complexation of Cd with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) in the presence of non-ionic micelles of Triton X-100. The effect of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction was studied. Under the optimum conditions, the detection limits are 0.64 ng mL^±1 with relative standard deviations (RSDs) of 2.1% (n = 10). The proposed method was applied to the determination of trace cadmium in water samples with satisfactory results.     

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.     

Cloud point extraction of lanthanide(III) ions via use of Triton X-100 without and with water-soluble calixarenes as added chelating agents

The use of water-soluble calixarenes: p-sulfonato thiacalixarene (ST), tetra-sulfonatomethylated calix[4]resorcinarene (SR), calix[4]resorcinarene phosphonic acid (PhR) as chelating agents in cloud point extraction (CPE) of La(III), Gd(III) and Yb(III) ions using Triton X-100 as non-ionic surfactant is introduced. The data obtained indicate that both complexation ability and structure of calixarenes govern the extraction efficiency of lanthanides. In particular ST and SR, forming 1:1 lanthanide complexes with similar stability in aqueous media, exhibit different extractability when used as chelating agents in CPE. First synthesized PhR was found to be the most efficient chelating agent exhibiting pH-dependent selectivity within La(III), Gd(III) and Yb(III) in CPE.     

Assessment of Inorganic Fibre Burden in Biological Samples by Scanning Electron Microscopy – Energy Dispersive Spectroscopy

A method based on cloud point extraction (CPE) separation/preconcentration of trace cadmium as a prior step to its determination by graphite furnace atomic absorption spectrometry (GFAAS) has been developed. If the system temperature is higher than the cloud point temperature (CPT) of the nonionic surfactant of p-octyl polyethyleneglycolphenyether (Triton X-100), the complex of Cd²⁺ with 1-(2-pyridylazo)-2-naphthol (PAN) could be extracted into surfactant-rich phase. The chemical variables affecting CPE were evaluated and optimized. Under the optimum conditions, preconcentrating 10.0 mL of water samples permitted a limit of detection of 5.9 ng · L⁻¹ (3σ) for cadmium with an enhancement factor of 50 and a relative standard deviation of 2.1% (n = 11, c = 2.0 ng · mL⁻¹). The method was applied to the determination of cadmium in reference material and water samples with satisfactory results.     

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.