Cloud point extraction equilibrium of lanthanum(III), europium(III) and lutetium(III) using di(2-ethylhexyl)phosphoric acid and Triton X-100

The cloud point extraction behaviors of lanthanoids(III) (Ln(III) = La(III), Eu(III) and Lu(III)) with and without di(2-ethylhexyl)phosphoric acid (HDEHP) using Triton X-100 were investigated. It was suggested that the extraction of Ln(III) into the surfactant-rich phase without added chelating agent was caused by the impurities contained in Triton X-100. The extraction percentage more than 91% for all Ln(III) metals was obtained using 3.0 × 10⁻⁵ mol dm⁻³ HDEHP and 2.0% (v/v) Triton X-100. From the equilibrium analysis, it was clarified that Ln(III) was extracted as Ln(DEHP)₃ into the surfactant-rich phase. The extraction constant of Ln(III) with HDEHP and 2.0% (v/v) Triton X-100 were also obtained.     

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.     

Detection of radionuclides in aqueous samples using cloud point extraction

A cloud point extraction method followed by inductively coupled plasma-mass spectrometry (ICP-MS) has been developed for the detection of trivalent lanthanides (Ln(III)) in aqueous samples. Ammonium pyrrolodinedithiocarbamate (APDC) was used as the chelating ligand with 2 wt% Triton X-114 as the surfactant. Various experimental parameters were investigated and the extraction efficiency, distribution ratios and concentration factors for the extraction of lanthanum (La), neodymium (Nd), europium (Eu) and thulium (Tm) were determined.     

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.     

Cloud point extraction preconcentration for capillary electrophoresis of metal ions

The application of the cloud point extraction (CPE) technique for capillary electrophoresis (CE) determination of metal ions was demonstrated using Cu(II) and Co(II) as model metal ions. The preconcentration of Cu(II) and Co(II) in aqueous solution was achieved by CPE with 1-(2-pyridylazo)-2-naphthol (PAN) as the chelating agent and Triton X-114 as the extractant. Baseline separation of the PAN chelates of Cu(II) and Co(II) was realized by CE with a photodiaode array detector in a  μm i.d. fused-silica capillary at 17 kV. A 50 mM NH₄Ac buffer solution (pH 8.0) containing 0.2 mM of PAN in 80% (v/v) of acetonitrile and 20% (v/v) doubly deionized water (DDW) was used as the separation medium to avoid the adsorption of hydrophobic substances and nonionic surfactant Triton X-114 onto the inner surface of the separation capillary, ensuring the separation efficiency and reproducibility. The precision (relative standard deviation (R.S.D.), n=5) for five replicate injections of a mixture of 20 μg/l of Co(II) and Cu(II) were 0.74 and 1.8% for the migration time, 3.1 and 0.64% for the peak area measurement, respectively. The apparent concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for CE separation and in the initial solution, was 15.9 for Co(II) and 16.3 for Cu(II). The linear concentration range was from 3 to 100 μg/l for both Co(II) and Cu(II). The detection limits of Co(II) and Cu(II) were 0.12 and 0.26 μg/l, respectively. The developed method was successfully applied to the determination of Co(II) and Cu(II) in tap water, snow water, and flavor wines.     

The application of cloud point preconcentration for the determination of Cu in real samples by flame atomic absorption spectrometry

A simple and practical preconcentration method using cloud point approach is proposed for the extraction and preconcentration of Cu (II). The analyte in the initial aqueous solution, acidified with HCl, is complexed with O,O-diethyldithiophosphate and Triton X-100 is added as a surfactant. After phase separation at 40°C based on cloud point of the mixture and dilution of the surfactant-rich phase with methanol, the enriched analyte is determined by flame atomic absorption spectrometry using conventional nebulization and the analytical wavelength used is 324.8 nm. The variables affecting the complexation and extraction steps were optimized. Under optimum conditions, preconcentration of 10 ml of sample in the presence of 0.1% (v/v) Triton X-100 permitted the detection of 0.94 ng ml⁻¹ of Cu. Analytical graphs were rectilinear in the concentration range of 5-200 ng ml⁻¹ and relative standard deviations were lower than 3%. The method affords recoveries in the range 97-101%. The method was successfully applied to the determination of Cu in drinking and rainwater, serum and human hair 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.     

A new sensitive method for the spectrophotometric determination of molybdenum using 3-hydroxy-2-(2'-thienyl)-4H-chromen-4-one

A spectrophotometric method has been developed for the determination of Molybdenum (VI) using 3-hydroxy-2-(2'-thienyl)-4H-chromen-4-one as a complexing agent. The complex formed was dissolved in water in the presence of Triton X-100 and exhibits an absorption maximum at 410 nm. A large number of metal ions like Co(II), Ni(II), Mn(II), Cr(III), Zn(II), Cu(II), Hg(II), Bi(III), Fe(II), Fe(III), Zr(IV), V(V) can be tolerated at an appreciable concentrations. Molar absorptivity and Sandell's sensitivity of the method is 2.80 x 10(5) l mol-1cm-1 and 3.42 x 10(-4) micrograms cm-2, respectively. Beer's law is obeyed in the concentration range of 0.01-0.4 ppm Mo(VI). Aliquots containing 0.2 ppm of Mo(VI) give a mean absorbance of 0.56 with a relative standard deviation of 1.3%.     

Cloud point extraction of iron(III) and vanadium(V) using 8-quinolinol derivatives and Triton X-100 and determination of 10(-7)moldm(-3) level iron(III) in riverine water reference by a graphite furnace atomic absorption spectroscopy

The cloud point extraction behavior of iron(III) and vanadium(V) using 8-quinolinol derivatives (HA) such as 8-quinolinol (HQ), 2-methyl-8-quinolinol (HMQ), 5-butyloxymethyl-8-quinolinol (HO₄Q), 5-hexyloxymethyl-8-quinolinol (HO₆Q), and 2-methyl-5-octyloxymethyl-8-quinolinol (HMO₈Q) and Triton X-100 solution was investigated. Iron(III) was extracted with HA and 4% (v/v) Triton X-100 in the pH range of 1.70-5.44. Above pH 4.0, more than 95% of iron(III) was extracted with HQ, HMQ, and HMO₈Q. Vanadium(V) was also extracted with HA and 4% (v/v) Triton X-100 in the pH range of 2.07-5.00, and the extractability increased in the following order of HMQ < HQ < HO₄Q < HO₆Q. The cloud point extraction was applied to the determination of iron(III) in the riverine water reference by a graphite furnace atomic absorption spectroscopy. When 1.25 × 10⁻³ M HMQ and 1% (v/v) Triton X-100 were used, the found values showed a good agreement with the certified ones within the 2% of the R.S.D. Moreover, the effect of an alkyl group on the solubility of 5-alkyloxymethyl-8-quinolinol and 2-methyl-5-alkyloxymethyl-8-quinolinol in 4% (v/v) Triton X-100 at 25 °C was also investigated.     

Synergistic cloud point extraction behavior of aluminum(III) with 2-methyl-8-quinolinol and 3,5-dichlorophenol.

The cloud point extraction behavior of aluminum(III) with 8-quinolinol (HQ) or 2-methyl-8-quinolinol (HMQ) and Triton X-100 was investigated in the absence and presence of 3,5-dichlorophenol (Hdcp). Aluminum(III) was almost extracted with HQ and 4(v/v)% Triton X-100 above pH 5.0, but was not extracted with HMQ-Triton X-100. However, in the presence of Hdcp, it was almost quantitatively extracted with HMQ-Triton X-100. The synergistic effect of Hdcp on the extraction of aluminum(III) with HMQ and Triton X-100 may be caused by the formation of a mixed-ligand complex, Al(dcp)(MQ)2.     

Speciation Determination of Chromium(VI) and Chromium(III) in Soil Samples after Cloud Point Extraction

Abstract

To measure the different activity of chromium(VI) and chromium(III) in soil samples, chromium(VI) and total chromium (CrVI + CrIII) was extracted by KCl extracting agent and alkali fusion, respectively. Cloud point extraction (CPE) for speciation determination of chromium with double-slotted quartz tube atom trap–flame atomic absorption spectrometry (STAT-FAAS) was developed. Preconcentration of chromium(VI) and total chromium in different pH solutions was achieved by CPE, with ammonium pyrrolidine dithiocarbamate (APDC) as the chelating agent and Triton X-114 as the cloud point extractant. The conditions of CPE and determination were studied. Under the optimal conditions, the enrichment factor was 50 for chromium from the initial 100-mL sample solution to the final 2-mL determined solution. Compared to the FAAS method, the sensitivity was improved seven-fold for chromium by the STAT-FAAS method. The limit of detection was 0.082 µg/L for chromium.     

浊点萃取-火焰原子吸收光谱法测定样品中的痕量钴

研究了基于表面活性剂Triton X-114和络合剂吡咯烷二硫代氨基甲酸铵（APDC）浊点萃取钴的样品前处理方法.优化了浊点萃取条件参数,包括pH值、Triton X-114用量、APDC浓度、平衡温度及时间等,建立了浊点萃取-火焰原子吸收光谱法测定痕量钴的方法.该法的检测限（3σ）为2.6μg/L,相对标准偏差RSD为6.2%（n=7,c=200μg/L）.该法成功地应用于海带、维生素B12注射液等样品中钴的测定.     

Uranium micelle-mediated extraction in acetate medium: factorial design optimization

A micelle-mediated extraction (CPE) procedure has been developed to remove trace amounts of uranium from wastewater using a non-ionic surfactant (Triton (X-100)) and lipophilic chelating extracting agent (D2EHPA) in acetate medium. The methodology used is based on the formation of metal complexes soluble in a micellar phase of a non-ionic surfactant. The uranyl ions complexes are then extracted into the surfactant-rich phase at a ambient temperature. The effects of different operating parameters such as the concentrations of Triton (X-100), D2EHPA and metal ions, temperature, sodium acetate rate and pH on the cloud point extraction of uranyl ions were studied in details and a set of optimum conditions were obtained. The results showed, without contribution of energy (ambient temperature), that up to 1000?ppm of uranyl ions can quantitatively be removed (>97?%) in a single CPE extraction using optimum conditions.     

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%.     

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.     

浊点萃取-火焰原子吸收光谱法测定食品和饮料中的痕量铜

研究了基于非离子表面活性剂TritonX-114和螯合剂二乙基氨基二硫代甲酸钠(DDTC)的浊点萃取-火焰原子吸收光谱法测定痕量铜的分析方法.考察了影响浊点萃取效率的参数,包括pH值、DDTC浓度、TritonX-114用量、平衡温度及时间等.在优化条件下,本法的检出限(3σ)为1.55μg/L,相对标准偏差RSD为3.4%(n=7,c=100μg/L),线性范围为0～250μg/L.将该法应用于茶叶标准样品(GBW07605)、奶粉和矿泉水等样品中痕量铜的测定,其回收率在96.7%～113.5%之间.     

The separation of aluminum(III) ions from the aqueous solution on membrane filter using Alizarin Yellow R

The membrane filtration was examined as an effective and selective method for collection of Al(III) ions from aqueous solutions using Alizarin Yellow R, one of a pH-indicator, as a precipitating reagent. For preparation of aqueous solutions without precipitate or turbidity, a non-ionic surfactant, Triton X-100, was used as a solubilizing reagent for insoluble materials. Three metal ions, Al(III), V(III) and Cu(II) ions, were able to be collected as yellow-orange precipitates from aqueous solutions controlled in a range of pH 4-7, pH 4-9, and pH 5.5-12, respectively, on a membrane filter by filtration under suction. Hydrogen peroxide and o-phenanthroline were found to be capable of masking V(III) and Cu(II) ions in a range of pH 5.5-8 in which Al(III) ions were collected. This membrane filtration was applied to selective separation and determination of Al(III) ions in tap water.     

Three-dimensional lanthanide(III)-copper(II) compounds based on an unsymmetrical 2-pyridylphosphonate ligand: an experimental and theoretical study

Based on an unsymmetrical 2-pyridylphosphonate ligand, two types of Ln(III)-Cu(II) compounds with three-dimensional structures were obtained under hydrothermal conditions, namely, Ln(2)Cu(3)(C(5)H(4)NPO(3))(6).4H(2)O (1.Ln; Ln=La, Ce, Pr, Nd) and Ln(2)Cu(3)(C(5)H(4)NPO(3))(6) (2.Ln; Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho). Compounds 1.Ln are isostructural and crystallize in chiral cubic space group I2(1)3. In these structures, each Ln ion is nine-coordinate and has a tricapped triprismatic geometry, while each Cu center is six-coordinate with an octahedral environment. The {LnO(9)} polyhedra and {CuN(2)O(4)} octahedra are connected by edge sharing to form an inorganic open framework structure with a 3-connected 10-gon (10,3) topology in which the Ln and Cu atoms are alternately linked by the phosphonate oxygen atoms. Compounds 2.Ln are isostructural and crystallize in trigonal space group R3. In these structures, the {LnO(6)} octahedra are triply bridged by the {CPO(3)} tetrahedra by corner sharing to form an infinite chain along the c axis. Each chain is connected to its six equivalents through corner sharing of {CPO(3)} tetrahedra and {CuN(2)O(2)} planes to form a three-dimensional framework structure in which the Ln and Cu atoms are linked purely by O-P-O units. The formation of these two types of structures is rationalized by quantum chemical calculations, which showed that both the lanthanide contraction and the electron configuration of Cu(II) play important roles. When Cu(II) was replaced by Zn(II), only the first type of compounds resulted. The magnetic properties of complexes 1.Ln and 2.Ln were investigated. The nature of Ln(III)-Cu(II) (Ln=Ce, Pr, Nd) interactions is illustrated by comparison with their Ln(III)-Zn(II) analogues.     

Extraction of lanthanum and gadolinium(III) at the cloud point using <Emphasis Type="Italic">p</Emphasis>-sulfonatocalyx[<Emphasis Type="Italic">n</Emphasis>]arenes as chelating agents

The extraction of gadolinium(III) and lanthanum(III) ions at the cloud point is studied in Triton X100 micellar solutions in a wide range of pH. In the absence of chelating agents, lanthanum(III) and gadolinium(III) ions are unselectively extracted at pH > 6. It is shown that the use of p-sulfonatothiacalyx[6(8)]arenes as chelating agents noticeably enhances the degree of extraction at pH 2–6. The composition and stability of lanthanum-p-sulfonatothiacalyx[n]arene complexes (n = 4, 6, 8) are estimated in a wide range of pH by pH-potentiometry. The degree of Gd³⁺ and La³⁺ ions extraction, which is performed at the cloud points employing calyxarene macrocycles of different sizes, is depended on the acidity of a medium.     

A Study on the Location and Aggregation of Tetrahydrophenylporphyrin with a Single Hexadecyl Chain in Triton X-100 Micelle

The location and aggregation of 5,10,15-tris(4-hydroxyphenyl)-20-(hexadecyloxyphenyl)porphyrin (P) in nonionic polyoxyethylene (9.5) octylphenol (Triton X-100) micelle solutions were studied by means of UV–Vis and fluorescence spectra. P forms premicelle surfactant–porphyrin aggregates when the surfactant concentration is below and approaching the CMC. In Triton X-100 micelle solutions, different types of H-aggregates of P were formed when the concentration of P is higher than 3.9×10^-6?mol?dm^-3. As the bulk pH is changed, a transfer process for the porphyrin moiety in Triton X-100 micelle occurs. In neutral Triton X-100 micelle solutions, P may be located at the inner layer of the micelle; in basic conditions, the porphyrin moiety may transfer to the outer surface of the micelle. The kinetic study of porphyrin complexed with Cu(II) in Triton X-100 micelle solutions shows that the metalation rate could be controlled by changing the pH.