Separation of niobium and tantalum through solvent extraction and reversed phase extraction chromatography using Aliquat 336 as an anion exchanger

Niobium and tantalum which have close chemical similarities have been separated through two different methods, viz. solvent extraction and reversed phase extraction chromatography (RPEC) in tracer scale using Aliquat 336 as a liquid anion exchanger. Quantitative extraction of tantalum in the organic phase from 0.05M HF solution by 5·10^–4M Aliquat 336 solution was achieved leaving niobium in the aqueous phase. In RPEC, hydrophobized kieselguhr impregnated with Aliquat 336 was used as the stationary phase in the column from which niobium was first eluted with 0.1M HF and then tantalum with 10M HNO₃ solution. The purity of the separated isotopes in both the procedures were verified by means of gamma-ray spectrometry.     

加速溶剂萃取-液相色谱-质谱/质谱法分析动物组织中的壬基酚、辛基酚和双酚A

建立了测定内分泌干扰物质烷基酚、双酚A的液相色谱-电喷雾串联质谱(负离子模式)分析方法,优化了样品前处理方法。以二氯甲烷作提取溶剂,采用加速溶剂萃取法萃取动物组织样品,萃取液用500 mg OASIS氨基固相萃取柱进行浓缩净化。对流动相组分和流动相添加剂对质谱的离子化效率进行了考察,测得3种化合物在高、中、低3个添加水平的回收率为88%~101%,相对标准偏差小于15%;双酚A、壬基酚和辛基酚的方法检出限分别为0.3, 0.05和0.1 μg/kg。对从北京市场上采集的27份动物组织样品进行检测,结果表明壬基酚广泛存在于各种动物源性食品中,检出含量为0.49~55.98 μg/kg,其中鱼肉组织中都检出壬基酚,而且其含量也较高(9.13~55.98 μg/kg)。     

The partition of ethoxylated non-ionic surfactants between two non-miscible phases

The partition of a polydispersed ethoxylated non-ionic surfactant in equilibrated oil–water systems has been studied at 25 °C. The model surfactant used was a commercial sample of nonylphenol ethoxylated with 10 moles of ethylene oxide (NPEO₁₀). The partition isotherms over the range of surfactant concentration including the critical micelle concentration (CMC) were made with n-hexane, i-octane and n-decane as oil phases. Each partition isotherm exhibits a change of slope that matched the CMC value of surfactant determined by surface tension measurements on aqueous solutions. During the partition of NPEO₁₀ in the oil–water systems, the oligomer distribution in the oil and water phases changed because of fractionation. Below CMC, the mean ethoxylation degree in the oil phase was smaller, whereas in water it was higher than the mean initial value of the surfactant. Moreover, the mean ethoxylation degree in both oil and water phase was practically independent of surfactant concentration. Above CMC, the mean distribution of ethoxymers decreased in both phases. This was ascribed to the competition between micelles from water and the oil phase for the more hydrophobic species of the surfactant. The mean distribution of ethoxymers in the aqueous phase asymptoted to a value that was the mean of the surfactant itself, whereas it steeply decreased in the organic phase.     

Solubilization of Perfluorodecalin in Aqueous Solutions of Dodecaethoxylated Nonylphenol

The solubilization of perfluorodecalin in aqueous solutions of dodecaethoxylated nonylphenol (Neonol AF_9–12) was studied by spectrometry, dynamic light scattering, and precision tensiometry. The aggregation numbers of Neonol AF_9–12 micelles, as well as the composition of micelles containing perfluorodecalin were determined. Within the framework of the pseudophase model, the partial coefficient of solubilizate distribution between micellar and aqueous phases and the standard Gibbs free energy of solubilization were calculated for the systems studied. It was shown that mixing of perfluorodecalin with Neonol AF_9–12 hydrocarbon radicals in micelle core is non-ideal.     

Selective separation and reversed phase extraction of zirconium and hafnium from a multitracer solution

The solvent extraction of Zr and Hf was studied using 444-trifluoro-1-(2-thienyl)-1,3-butanedione (TTA) from a multitracer solution containing carrier-free radioisotopes of Zr, Hf, and other elements. The multitracer was prepared from Au foil irradiated with high-energy heavy-ion beams. Effects of HCl and HNO₃ concentrations and organic solvent on the extraction and coextraction of other radionuclides have been studied. It was found that decalin (decahydronaphthalene) was the best solvent among 14 solvents studied and the optimum aqueous phase was 2 mol·dm^–3 HCl or HNO₃. About 2–10% of Sr, Rb, Sc and Nb were coextracted with Zr and Hf. The reversed phase extraction of Zr and Hf was also developed by using ethylenediaminetetraacetic acid (EDTA) solution at pH range of 8.5–10.     

Extraction of rare earth elements with organophosphorus extractants as carriers in supported liquid membranes

The membrane extraction of Y, Ce, Eu, Tm and their binary mixtures Ce–Y, Ce–Eu, Ce–Tm with supported liquid membranes containing TBP and HDEHP as carriers in decanedodecane hydrocarbon solvent, has been studied. Upon extraction with TBP aqueous nitrate solutions of rare earth elements (REE) were used as feed phase. In some cases they also contained EDTA or DCTA. In most cases, the receiving phase was an aqueous solution of EDTA. Extraction with HDEHP was performed from nitrate and chloride solutions and the receiving phase was the corresponding dilute acid. Pertraction of an element through a membrane was studied as a function of time and of initial composition of phases. The results are presented in the following forms: flux of metal through membrane, coefficients of permeability, separation factors and effective diffusion coefficients.     

Microfluidic Chip-Based Induced Phase Separation Extraction as a Fast and Efficient Miniaturized Sample Preparation Method

Induced phase separation extraction (IPSE) is an efficient sample clean-up technique that can replace liquid-liquid extraction (LLE). The purpose of this study was to miniaturize IPSE by carrying it out in a microfluidic chip. An IPSE chip was designed and evaluated for its ability to separate and purify samples on a microscale. The 5 × 2 cm chip was fed with a solution of polar to non-polar model compounds in acetonitrile-water (1:1). In the 100 µm wide and 40 µm deep microchannels, the sample solution was efficiently separated into two immiscible phases by adding a hydrophobic solvent as inducer. Analytes present in the sample solution each migrated to their own favorable phase upon phase separation. After optimization, extraction and fractionation were easily and efficiently achieved. The behavior of analytes with a pH-dependent partitioning could be influenced by adjusting the pH of the sample solution. Scutellaria baicalensis extract, used in Traditional Chinese Medicine (TCM), was successfully separated in aglycones and glycosides. In this microscale system, the sample and solvent consumption is reduced to microliters, while the time needed for the sample pretreatment is less than one minute. Additionally, the extraction efficiency can reach up to 98.8%, and emulsion formation is avoided.     

Microwave extraction of phthalate esters from marine sediment and soil

Summary As part of an on-going ASEAN⁺⁾-Canada Cooperative Programme on Marine Science, microwave-assisted solvent extraction has been employed for the extraction of six phthalate esters from marine sediment and soil samples. Five of the six esters studied are among the United States Environmental Protection Agency's list of top priority pollutants. The effects of extraction solvent, extraction temperature, duration of extraction and extraction volume on the mean recoveries of the six phthalate esters were quantitatively evaluated by means of an analysis of variance, followed by testing the differences among the level means for each condition with least significant difference method. Microwave-assisted solvent extraction allowed comparable or higher recoveries of the six phthalate esters (70.1–91.0%) in comparison with conventional soxhlet (65.5–89.5%) and sonication (64.6–88.6%). The precision of results by microwave-assisted solvent extraction was improved significantly compared to the conventional techniques. The microwave extraction system has many advantages over the soxhlet and sonication extraction, e.g., no laborious clean-up procedure, lower usage of hazardous organic solvent, and larger sample throughput. The technique has been employed for the analysis of native marine sediment and soil samples in Singapore.     

Determination of nonylphenol and nonylphenol ethoxylates in wastewater using MEKC

Nonylphenol ethoxylates (NPEO_x) are surfactants which are used worldwide and can be transformed in the environment by microorganisms to form nonylphenol (NP). Analysis of these compounds was carried out with micellar electrokinetic capillary chromatography (MEKC). Different parameters such as background electrolyte (BGE) solution, pH, type of surfactant, and sample stacking were optimized. The use of CHES (20 mM, pH 9.1) in combination with 50 mM sodium cholate as a surfactant as BGE solution, together with sample stacking using 50 mM NaCl in the sample and an injection time of 20 s, provided the best separation of the compounds studied. The method was applied to the determination of target analytes in two types of sludge water coming from two steps of a wastewater treatment plant. Liquid–liquid extraction was carried out using toluene as solvent, resulting in recoveries around 100% for all studied analytes. The presence of NPEO_x was observed in the first step of the sludge water treatment, based on migration time and UV spectra. Identification was confirmed using tandem MS. LOQs of the studied compounds were in the range of 12.7 to 30.8 ng/mL, which is satisfactory for the analysis of real wastewater samples.     

固相萃取-高效液相色谱法测定水中BPA、NP和OP含量

采用国产新型D4020大孔吸附树脂自制固相萃取柱,研究了柱长、上样速度、样品溶液的pH、盐浓度等因素对壬基酚、辛基酚和双酚A吸附率的影响,确定了最佳固相萃取条件,建立了固相萃取-高效液相色谱测定水中痕量壬基酚、辛基酚和双酚A的分析方法.该法双酚A、壬基酚和辛基酚的检出限分别为0.432 μg/L、0.998 μg/L和1.336 μg/L,回收率为91%～96%,相对标准偏差(RSD)为1.5%～5.6%.方法简便快速、成本低廉,灵敏度高,准确度好,用于实际水样分析,取得满意结果.     

Membrane extraction of pertechnetate with quaternary ammonium salts comparison with solvent extraction

The liquid membrane extraction (MX) and the solvent extraction (SX) of pertechnetate with Aliquat 336 as a carrier has been studied. From the results of SX the percentage of pertechnetate in the inner solution in experiment with LM was proposed. It has been found that the pertraction of pertechnetate depends on the inner solution used and the most effective solutions were those with ClO ₄ ^– and SCN^–. Effects of the carrier concentration in membranes and outer phase composition have been studied too. The results of these experiments were kinetic curves with a minimum, which may be interpreted as a result of competing processes in the systems.     

Comparison of extraction techniques of robenidine from poultry feed samples

In this paper, effectiveness of six different commonly applied extraction techniques for the determination of robenidine in poultry feed has been compared. The sample preparation techniques included shaking, Soxhlet, Soxtec, ultrasonically assisted extraction, microwave – assisted extraction and accelerated solvent extraction. Comparison of these techniques was done with respect to the recovery extraction, temperature and time, reproducibility and solvent consumption. Every single extract was subjected to clean – up using aluminium oxide column (Pasteur pipette filled with 1 g of aluminium oxide), from which robenidine was eluted with 10 ml of methanol. The eluate from the clean-up column was collected in a volumetric flask, and finally it was analysed by HPLC–DAD–MS. In general, all extraction techniques were capable of isolating of robenidine from poultry feed, but the recovery obtained using modern extraction techniques was higher than that obtained using conventional techniques.

In particular, accelerated solvent extraction was more superior to other techniques, which highlights the advantages of this sample preparation technique. However, in routine analysis, shaking and ultrasonically assisted extraction is still the preferred method for the solution of robenidine and other coccidiostatics.     

磁性碳纳米管表面新型壬基酚印迹纳米复合材料制备及吸附性能

采用聚苯胺包覆的磁性多壁碳纳米管为载体,以壬基酚(NP)为模板分子,甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂制备新型磁性壬基酚印迹复合萃取材料。 采用扫描电子显微镜(SEM)、红外光谱(FT-IR)和样品振动磁强计(VSM)等技术手段对该磁性印迹复合材料进行表征和分析,结果表明,在磁性碳纳米管表面成功接枝厚度为60~70 nm的印迹聚合层。 采用高效液相色谱(HPLC)技术对该印迹复合材料的吸附性能进行探讨,结果表明,该磁性印迹复合材料对壬基酚具有特异性吸附性能,最大吸附量为38.46 mg/g。 结合HPLC检测技术,该磁性印迹复合材料成功用于分离富集饮用水中的壬基酚。     

Extraction of biogenic amines and their dansyl derivatives with reverse microemulsions of bis [2-ethylhexyl] sulphosuccinate (AOT) prior to high-performance liquid chromatographic determination

The ability of reverse microemulsions of the surfactant bis [2-ethylhexyl] sulphosuccinate (AOT) in heptane to extract and preconcentrate eight biogenic amines present in aqueous matrices has been explored. The “phase transfer” method, in which the surfactant solution is contacted with an aqueous salt solution containing the analytes, has been used as the analytical methodology. The extraction efficiencies have been compared with those obtained by using the “cloud point” extraction technique with Triton X-114 as surfactant, and with methylene chloride as a typical extracting solvent. In order to improve extraction and detection as compared with the underivatized amines, the fluorescent reagent dansyl chloride has been used to obtain the more hydrophobic and thus, easily extractable dansyl derivatives. Although extraction of most of the biogenic amines is high, extraction of their dansyl derivatives is practically 100%. The procedure was successfully applied to the analysis of commercial fruit juices. The analytical methodology is sensitive, fast, simple and reproducible. The LOD were in the vicinity of 1 and 2 pmol, which is similar or better than other techniques. The micellar phase is compatible with reverse phase HPLC mobile phases, which allow direct injection of the analyte after extraction. This is an advantage over solid phase extraction (SPE), where incomplete recovery can occur. Moreover, AOT showed to be better extracting surfactant for biogenic amines (and their corresponding dansyl derivatives) than Triton X-114 at the same concentration.     

Influence of Tetraethoxylated Nonylphenol on the Properties of Dodecaethoxylated Nonylphenol Micelles in Aqueous Medium

Properties of the mixed micelles of tetraethoxylated nonylphenol and dodecaethoxylated nonylphenol (NP₁₂) in water are studied by spectrophotometry, dynamic and static light scattering methods. Data on the composition, aggregation numbers (N), sizes (R _h), and hydration (n _OE) of mixed and individual micelles of NP₁₂ are obtained. Two NP₁₂ concentration regions are disclosed where mixed micelles of various compositions but with the close values of N, R _h, and n _OE are present. It is established that the sizes and aggregation numbers of mixed micelles are noticeably larger than those of individual micelles. Features of the mixing of two studied surfactants in a micellar state are analyzed in terms of the theory of phase separation.     

Extraction of polyvanadates by means of amines

The present paper is aimed at obtaining quantitative information on the extraction of polyvanadates from aqueous solutions with benzene solutions of tri-n-octylamine and Primene JMT with respect to initial pH value of aqueous solution and the ratio of volumes of the organic and aqueous phase. The predominant species in acidic solutions at concentrations in excess of 0.01 M are decavanadates. The extraction equilibria were studied within the range of pH 2–4. At this concentration of sulfuric acid the species V₁₀O₂₆(OH)^4– and V₁₀O₂₇(OH)^5– prevail. Supposing that the nonideality of the aqueous phase does not play an important role and that the activity coefficient of the amine sulfate remains constant, the nonideal behavior of the extraction system can be explained by the hydration of complexes in the organic phase. On the basis of suggested reactions and mass balance equations the comparison of experimental and calculated equilibrium data was done.     

Molecularly imprinted solid phase extraction for rapid screening of metformin

A molecularly imprinted solid phase extraction (MISPE) method has been developed for the rapid screening of metformin. Newly synthesized molecularly imprinted polymer (MIP) particles were slurry-packed into a micro-column for selective solid phase extraction (SPE) of metformin. With CH₃CN flowing at 0.5 ml/min, a total binding capacity of 1600 ng metformin was determined for the 20 mg of MIP particles. A broad range of MISPE conditions was evaluated with respect to sample solvent, pH, and buffer compositions. A 95±2% binding could be achieved from one 20-μl injection of sample solution in acetonitrile plus phosphate buffer, up to 1200 ng of metformin. However, the micro-column interacted indiscriminately with phenformin, a structural analogue, to attain 49±2% binding. Separation of phenformin from metformin was ultimately achieved, using differential pulsed elution (DPE) with 1 M trifluoromethacrylic acid in acetonitrile. Final pulsed elution (FPE) using 3% trifluoroacetic acid in methanol was good for the quantitative elution of metformin. The MISPE–DPE–FPE method, with UV detection at 240 nm, afforded a detection limit of 0.8 μg/ml (or 16 ng) for metformin. Each MISPE–DPE–FPE analysis required less than 5 min to complete.     

LC Determination of Mono-Substituted Phenols in Water Using Liquid–Liquid–Liquid Phase Microextraction

A simple liquid–liquid–liquid microextraction device of new design was used to pre-concentrate phenols from water samples before liquid chromatographic (LC) analysis. Extraction was induced by the pH difference inside and outside an organic phase located at the interface. The pH of the donor phase outside the organic phase was adjusted to 1 with HCl whereas the acceptor phase was a basic solution at pH 13. On stirring neutral phenols were extracted into the organic solvent then back-extracted into 1 μL of basic acceptor solution suspended from the tip of a micro syringe. The acceptor phase was then withdrawn into the micro syringe and injected directly into the LC. The technique uses a low-cost disposable extraction ‘device’ and is very convenient to operate. Up to 230-fold enrichment of analytes could be achieved. This procedure could also serve as a sample clean-up step because neutral and basic compounds were not extracted into the acceptor phase. The RSD (n = 5) was better than 6.2% and the linear calibration range was from 1 to 1000 µg–L⁻¹ with r ² ≥ 0.992.Optimization of experimental conditions (rate of stirring, ionic strength of the sample solution, concentration of reagents, time of extraction, and organic solvent volume) were also examined. The method was applied to the determination of phenols in tap and well waters.Revised: 14 February and 29 March 2005     

Extraction of thorium from aqueous nitric acid solution by bis-2-(butoxyethyl ether) (DBC)

The solvent extraction of thorium(IV) (4.3·10^–4M) from nitric acid solution by bis-2-(butoxyethyl ether) (butex or DBC) has been studied. It has been investigated as a function of nitric acid, extractant and metal ion concentration. The effect of equilibration time, diverse ions and salting-out agent on the extraction has also been examined. Among anions, fluoride, phosphate, oxalate and perchlorate have reduced the extraction. Cations such as Na(I), K(I), Ca(II), Zn(II), Al(III), Ti(IV), Zr(IV) except Sr(II) and Pb(II) do not interfere in the extraction. The extraction is enhanced upto 97% in three stages at 6M HNO₃ having 2.94M NaNO₃ as salting-out agent. The extraction is found to be independent of thorium concentration in the range studied (4.3·10^–4–4.3·10^–2M). The temperature (18–45°C) has an adverse effect on the extraction. A 1% solution of ammonium bifluoride is found to be a good stripping solution and recovery of thorium is >98%.     

Determination of some selected polycyclic aromatic hydrocarbons in environmental samples by high-performance liquid chromatography with fluorescence detection

Summary Analytical methods for the determination in environmental samples, of some selected Polycyclic Aromatic Hydrocarbons (PAH's), which are included on the EPA Priority Pollutant list, have been developed and evaluated. The methodology involves the extraction of PAH's from water samples by solvent extraction with dichloromethane. Solid samples were ultrasonically extracted with acetone/hexane and the extract was cleaned up on a silica gel/alumina column. The concentrated and cleaned up extracts were analysed by HPLC on a polymeric C₁₈ column using a gradient of acetonitrile/water as the mobile phase and fluorescence detection. Typical detection limits lie in the range of 1–30 ng ml^–1 of the analytes, but after sample pretreatment detection limits of 10–300 ng l^–1 were obtained. The extraction, clean-up and HPLC methodology was applied to the determination of selected PAH's in coal washings samples and the method was validated by the quantification of PAH's in a natural contaminated and a spiked sediment.