Group separation of trace rare-earth elements by countercurrent chromatography for their determination in high-purity calcium chloride

A method has been developed for the separation of the entire group of rare-earth elements from high-purity calcium chloride by countercurrent chromatography, and subsequent determination of the elements by ICP– MS. A solution of diphenyl[dibutylcarbamoylmethyl]phosphine oxide in chloroform (0.5 mol L^–1) has been chosen as reagent for the extraction and preconcentration of trace rare-earth elements from aqueous 5% CaCl2 solution, 3 mol L^–1 in HNO3 and 0.1 mol L^–1 in HClO4. The analytes are back-extracted into a small volume of water and the aqueous eluate is subjected to ICP–MS measurements. The performance characteristics of the procedure developed have been checked by use of the standard addition technique and a real CaCl2 sample (Merck product) has been analyzed. The results obtained demonstrate the applicability of countercurrent chromatography to the determination of ultratrace elements. Received: 6 December 2000 / Revised: 27 February 2001 / Accepted: 6 March 2001     

Enrichment of rare-earth elements (REE) and Gd-DTPA in surface water samples by means of countercurrent chromatography (CCC)

An analytical scheme was developed for the determination of rare-earth elements and gadolinium diethylenetriaminepentaacetate (Gd-DTPA) in river water by ICP-MS. Since the concentration of Gd-DTPA and the rare-earth elements in river water is often lower than the limits of detection in quadrupole ICP-MS applying pneumatic nebulization, a preconcentration procedure is essential.In this work, the capabilities of countercurrent chromatography (CCC) for preconcentration of REE were investigated. For preconcentration ethylhexylphosphates as stationary phase had been used. Acidified aqueous samples (pH 2) and river water spiked with REE and Gd-DTPA were under study. The procedure was compared with solid phase extraction (SPE) using the same samples and ethylhexylphosphates as stationary phase. The recovery of the light and middle REE was found to be at about 100%, which was found to be more efficient than applying SPE. In contrast, the recovery rates for Yb and Lu were low (and poorly reproducible) using CCC (57% and 73%, respectively) while significant better results were obtained with SPE (89% and 84%, respectively).The recoveries of Gd applying Gd-DTPA were 80 ± 4% in the investigation of river water samples.     

Application of pH‐zone‐refining countercurrent chromatography in the chiral separation of two β‐adrenergic blocking agents

Two β‐adrenergic blocking agents, 1‐[(1‐methylethyl)amino]‐3‐phenoxy‐2‐propanol ( 1 ) and 1‐[(1‐methylethyl)amino]‐3‐(3‐methylphenoxy)‐2‐propanol ( 2 ; Toliprolol), were enantioseparated by pH‐zone‐refining countercurrent chromatography. A two‐phase solvent system composed of chloroform containing 0.10 mol/L of di‐n‐hexyl l‐ tartrate/0.10 mol/L of boric acid aqueous solution (1:1, v/v) was selected, in which 20 mmol/L triethylamine was added in the organic phase as a retainer and 2 mmol/L HCl was added in the aqueous phase as an eluter. Fifty milligrams of each racemate was completely enantioseparated by pH‐zone‐refining countercurrent chromatography to yield each enantiomer with a purity of more than 98%, and the recovery of each separated enantiomer reached around 76–82%.     

Analysis of etimicin sulfate by liquid chromatography with pulsed amperometric detection

A new method for determination of etimicin's (ETM) purity and content is developed by liquid chromatography (LC) and pulsed amperometric detection (PAD). A reversed-phase ion-pair LC method with pulsed amperometric detection on a gold electrode after post-added NaOH is described. The mobile phase consisted of an aqueous solution containing 0.033 mol L(-1) oxalic acid, 0.012 mol L(-1) heptafluorobutyric acid, and 210 mL L(-1) acetonitrile with pH 3.40 adjusting by dilute NaOH solution. The total analysis time was not more than 30 min. The effects of the different chromatographic parameters on the separation were also investigated. A number of commercial samples of etimicin sulfate were analyzed using this method.     

应用离子色谱离线螯合及ICP-MS测定海水中多种痕量元素

简要介绍如何构建和运用离子色谱离线螯合系统结合ICP-MS方法分析海水中的痕量元素.     

A new method for the determination of the critical micelle concentration of Triton X-100 in the absence and presence of beta-cyclodextrin by resonance Rayleigh scattering technology

A new method for the determination of the critical micelle concentration (CMC) of Triton X-100 in aqueous solution and beta-cyclodextrin solution by resonance Rayleigh scattering (RRS) has been developed. The method is based on the measurement of the RRS intensity of different concentration of Triton X-100 in aqueous solution and beta-cyclodextrin solution (6.0 x 10(-4) mol l(-1)). When the RRS intensities were plotted against the concentration of Triton X-100, an inflection point appeared at the Triton X-100 concentration of 5.0 x 10(-4) mol l(-1) in aqueous solution and 1.1 x 10(-3) mol l(-1) in beta-cyclodextrin solution, respectively. These values of concentration corresponded to the CMC of Triton X-100 in aqueous solution and beta-cyclodextrin solution, which also agreed closely with the results reported by surface tension and UV-Vis absorption spectrophotometry. Therefore, the present RRS method is very convenient, rapid and accurate and can be used as a new technology for the determination of CMC values of surfactants without any probe. The relationship between the RRS intensity and the concentration, aggregate state and the aggregate molecular size of Triton X-100 has been primarily discussed.     

高效液相色谱-二极管阵列检测器同时测定化妆品中的九种染料及中间体

建立了用高效液相色谱-二极管阵列检测器(HPLC-PDA)同时检测9种染料及中间体的系统方法。首先采用超声提取的方法处理样品,对提取溶剂和提取时间进行了选择,确定用甲醇-0.01 mol/L 乙酸铵(体积比为2∶1)作提取溶剂,超声提取20 min。然后,采用C18柱,以甲醇-0.01 mol/L乙酸铵(pH 6.2)为流动相梯度洗脱,用PDA检测。以保留时间定性,并以紫外吸收光谱图辅助定性,以外标法定量。定量检测波长为230 nm,15 min内可对9种目标物同时进行测定,且各化合物都达到基线分离(分离度大于1.5)。经测定,该方法的平均回收率(n=8)为81.0%～105.6%,相对标准偏差（RSD）为0.8%～4.9%,检出限(以信噪比为3计)为0.1～2 μg。该方法简单、快速,能有效提取和分离测定化妆品中9种染料及中间体。将该方法用于实际化妆品样品的检测,结果令人满意。     

逆流色谱分离感应耦合等离子质谱在线测量超痕量钚

将逆流色谱（CCC）与感应耦合等离子质谱（ICP-MS）相联,研究了几种两相体系在CCC中的固定相保留率,从中选择1％TNOA-正庚烷作固定相,通过CCC富集分离钚并去除基体及干扰元素,通过研究在线分离条件及定量方法等,建成了CCC分离ICP—MS在线测量超痕量钚的方法。采用该方法分析得到实际土壤样品中^239Pu的含量与由传统的分离方法给出的结果相吻合。     

磷酸三丁酯萃淋树脂色层分离电感耦合等离子体质谱法测定富稀土样中微量铀和钍

研究了磷酸三丁酯萃淋树脂色层分离,电感耦合等离子体质谱法测定富稀土样中微量铀、钍的方法。样品经消解后,以磷酸三丁酯萃淋树脂为固定相、8 mol/L硝酸为流动相过柱分离,样品中的大部分稀土元素随流动相流出,而铀和钍则被固定相吸附,用去离子水洗脱后,再用电感耦合等离子体质谱仪测定。铀、钍的检出限分别为0.06,0.16μg/L,测定结果的相对标准偏差均小于10%(n=5),加标回收率为98%~105%。对稀土矿石标准物质进行测定,测定值与推荐值相符。该法操作简便,测定结果可靠,适于富稀土样中微量铀、钍的测定。     

Spectrophotometric determination of the total amount of rare-earth elements in agricultural samples with p-chloro-chlorophosphonazo

A simple, sensitive and accurate spectrophotometric method for determination of the total amount of rare-earth elements in agricultural samples with p-chloro-chlorophosphonazo [pCCPA, i.e., 2-(4'-chloro-2'-phosphon-benzylazo)-7-(4'-chlorophenyl)-1,8-dihydroxynaphthalene-3,6-disulphonic acid] in sulphuric acid medium has been developed. The apparent molar absorptivity of RExOy (the general formula of rare-earth oxides)-pCCPA complex is 8.17 x 10(4) 1.mole(-1) cm(-1) at 676 nm, and Beer's law is obeyed for the mixture of RExOy in the range 0-12 mug/25 ml. The proposed method has been successfully applied to the determination of the total amount of rare-earth elements in soils, herbs, vegetables, dried stems of maize, water samples and rare-earth microelement fertilizer samples with satisfactory results.     

Flow injection on-line solid phase extraction coupled with inductively coupled plasma mass spectrometry for determination of (Ultra)trace rare earth elements in environmental materials using maleic acid grafted polytetrafluoroethylene fibers as sorbent

A new sorbent, maleic acid grafted polytetrafluoroethylene fiber (MA-PTFE), was prepared and evaluated for on-line solid-phase extraction coupled with inductively coupled plasma mass spectrometry (ICP-MS) for fast, selective, and sensitive determination of (ultra)trace rare earth elements (REEs) in environmental samples. The REEs in aqueous samples at pH = 3.0 were selectively extracted onto a microcolumn packed with the MA-PTFE fiber, and the adsorbed REEs were subsequently eluted on-line with 0.9 mol l(-1) HNO3 for ICP-MS determination. The new sorbent extraction system allows effective preconcentration and separation of the REEs from the major matrix constituents of alkali and alkali earth elements, particularly their separation from barium that produces considerable isobaric interferences of 134Ba16O1H+, 135Ba16O+, 136Ba16O1H+, and 137Ba16O+ on 151Eu+ and 153Eu+. With the use of a sample loading flow rate of 7.4 ml min(-1) for 120 s preconcentration, enhancement factors of 69-97 and detection limits (3s) of 1-20 pg l(-1) were achieved at a sample throughput of 22 samples h(-1). The precision (RSD) for 16 replicate determinations of 50 ng l(-1) of REEs was 0.5-1.1%. The developed method was successfully applied to the determination of (ultra)trace REEs in sediment, soil, and seawater samples.     

Fast speciation analysis of iodophenol compounds in river waters by capillary electrophoresis-inductively coupled plasma-mass spectrometry with off-line solid-phase microextraction

An analytical methodology for the fast separation and determination of iodophenol species in natural water samples was developed using capillary electrophoresis (CE) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Based on the element-specific and highly sensitive detection provided by ICP-MS, the methodology has been applied to the analysis of 2-iodophenol, 4-iodophenol, and 2,4,6-triiodophenol. The use of solid-phase microextraction (SPME), after proper optimization, improved the signal by a factor of 100 leading to detection limits in the sub microg.L(-1). Different desorption conditions of iodophenol compounds from the SPME microfiber were studied to achieve the optimum preconcentration factor and best analytical performance. Different CE conditions were studied to achieve complete baseline separation of iodophenols in short migration times. Three different CE buffer systems were evaluated using ICP-MS detection. A buffer solution containing 20 mmol.L(-1) 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and an applied potential of +22 kV were finally selected leading to a maximum separation time of 6.6 min. A relative standard deviation (%RSD) of about 5.0% for ten consecutive determinations was obtained. Finally, the speciation methodology developed was utilized for the determination of iodophenol compounds in natural water samples.     

Solvent extraction-spectrophotometric determination of rare earths with chlorophosphonazo-III

The rare-earth chlorophosphonazo III chelates are easily extracted from an aqueous solution (pH 1.1-1.5) into n-butanol. The absorbance at the absorption maximum (at 668 nm) is about 3 times that in aqueous solution. The spectrophotometric determination of rare earths has been investigated.     

Determination of trace cadmium in waters by flame atomic absorption spectrophotometry after preconcentration with 1-nitroso-2-naphthol-3,6-disulfonic acid on Ambersorb 572

A procedure for the determination of trace amount of cadmium after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been proposed. This chelate is adsorbed on the adsorbent in the pH range 3-8 from large volumes of aqueous solution of water samples with a preconcentration factor of 200. After being sorbed, cadmium was eluted by 5 mL of 2.0 mol L(-1) nitric acid solution and determined directly by flame atomic absorption spectrophotometery (FAAS). The detection limit (3sigma) of cadmium was 0.32 microg L(-1). The precision of the proposed procedure, calculated as the relative standard deviation of recovery in sample solution (100 mL) containing 5 microg of cadmium was satisfactory (1.9%). The adsorption of cadmium onto adsorbent can formally be described by a Langmuir equation with a maximum adsorption capacity of 19.6 mg g(-1) and a binding constant of 6.5 x 10(-3) L mg(-1). Various parameters, such as the effect of pH and the interference of a number of metal ions on the determination of cadmium, have been studied in detail to optimize the conditions for the preconcentration and determination of cadmium in water samples. This procedure was applied to the determination of cadmium in tap and river water samples.     

Determination of lanthanum and rare earth elements in bovine whole blood reference material by ICP-MS after coprecipitation preconcentration with heme-iron as coprecipitant

An analytical method for the determination of lanthanide elements in the bovine whole blood reference material (IAEA A-13) has been investigated by inductively coupled plasma mass spectrometry (ICP-MS). The bovine whole blood reference material was digested with HNO₃ and HClO₄, and then the pH of the digested solution was adjusted to 12 with 3 M sodium hydroxide aqueous solution. In this experimental procedure, lanthanide elements in the blood sample were coprecipitated with iron mainly derived from heme-iron in blood itself. In order to minimize matrix effects due to iron, excess iron in the analysis solution was removed by solvent extraction using methyl isobutyl ketone (MIBK) prior to the determination of lanthanide elements by ICP-MS. The recoveries of all lanthanide elements were almost quantitative in the recovery test. In consequence, it has been found that all lanthanide elements in bovine whole blood reference material are at the wide concentration range of 0.90 pg/g for Tm ∼1880 pg/g for Ce. Received: 2 May 1998 / Revised: 27 July 1998 / Accepted: 30 July 1998     

Determination of lanthanum and rare earth elements in bovine whole blood reference material by ICP-MS after coprecipitation preconcentration with heme-iron as coprecipitant

An analytical method for the determination of lanthanide elements in the bovine whole blood reference material (IAEA A-13) has been investigated by inductively coupled plasma mass spectrometry (ICP-MS). The bovine whole blood reference material was digested with HNO₃ and HClO₄, and then the pH of the digested solution was adjusted to 12 with 3 M sodium hydroxide aqueous solution. In this experimental procedure, lanthanide elements in the blood sample were coprecipitated with iron mainly derived from heme-iron in blood itself. In order to minimize matrix effects due to iron, excess iron in the analysis solution was removed by solvent extraction using methyl isobutyl ketone (MIBK) prior to the determination of lanthanide elements by ICP-MS. The recoveries of all lanthanide elements were almost quantitative in the recovery test. In consequence, it has been found that all lanthanide elements in bovine whole blood reference material are at the wide concentration range of 0.90 pg/g for Tm ∼1880 pg/g for Ce. Received: 2 May 1998 / Revised: 27 July 1998 / Accepted: 30 July 1998     

Enantioselective determination of the organochlorine pesticide bromocyclen in spiked fish tissue using solid-phase microextraction coupled to gas chromatography with ECD and ICP-MS detection

A method for enantioselective determination of bromocyclen enantiomers in fish tissue has been developed. The enantiomers were resolved by capillary gas chromatography (GC) using a commercial chiral column (CP-Chirasil-Dex CB) and a temperature program from 50 degrees C (held for 1 min), raised to 140 degrees C at 40 degrees C min(-1) and then raised at 0.2 degrees C min(-1) to 155 degrees C. This enantioselective gas chromatographic separation was combined with a clean-up/enrichment procedure based on solid-phase microextraction (SPME). Under SPME optimized conditions, precision, linearity range and detection limits of the developed SPME-enantioselective GC procedure were evaluated and compared using two different detection systems: a classical electron-capture detection (ECD) and an element specific detection using inductively coupled plasma mass spectrometry (ICP-MS). The SPME-GC-ECD method exhibited an excellent sensitivity, with detection limits of 0.2 ng L(-1) for each enantiomer of bromocyclen. Although ICP-MS offered poorer detection limits (7 ng L(-1) as Br, equivalent to 36 ng L(-1) of each enantiomer) than conventional ECD detector, it proved to be clearly superior in terms of selectivity. The relative potential and performance of the two compared methods for real-life analysis has been illustrated by the determination of enantiomers of bromocyclen in spiked tissue extracts of trout.     

Highly sensitive sensing of zinc(II) by development and characterization of a PVC-based fluorescent chemical sensor

A sensor membrane with excellent performance based on 1-methyl-1-phenyl-3-[1-hydroxyimino-2-(succinimido)ethyl]cyclobutane has been developed for the determination of zinc(II) ions. The sensing membrane is capable of determining zinc(II) with an outstanding high selectivity over a dynamic range between 8.0×10(-8) and 1.6×10(-4) mol L(-1) with a limit of detection of 2.5×10(-8) mol L(-1) (1.6 μg L(-1)). It can be easily and completely regenerated by using 0.1 mol L(-1) EDTA solution. The optical sensor developed here was found to be stable, cost effective, easy to prepare, and has unique selectivity towards Zn(2+) ion with respect to common metal ions. The proposed sensor was then applied for the determination of zinc in tap water and hair samples with satisfactory results.     

Selective leaching of elements associated with Mn - Fe oxides in forest soil, and comparison of two sequential extraction methods

For selective dissolution of Mn oxides as components of soil (easily reducible oxides) 0.05 mol L(-1) and 0.1 mol L(-1) NH2OH.HCl acidified to pH 2 and for dissolution of Fe oxides (crystalline form of the oxides) 0.25 mol L(-1) NH2OH.HCl in 25% acetic acid, 0.2 mol L(-1) oxalate buffer and 0.1 mol L(-1) ascorbic acid in oxalate buffer were tested. Dissolved elements were determined by ICP-MS and ICP-OES. The studies indicate that the use of 0.05 mol L(-1) NH2OH.HCl in nitric acid solution (pH 2) and 0.1 mol L(-1) ascorbic acid in 0.2 mol L(-1) oxalate buffer led to selective leaching of trace metals bound by Mn and Fe oxide phases in soil. Comparison of different extraction schemes indicates that the trace elements investigated are mainly bound to minerals consisting of crystalline Fe oxides and insoluble minerals (under the extraction conditions used). The studies also indicate that Mn oxides and organic matter retain a major mobile fraction of the elements investigated in the soil.     

Determination of rare earth elements in Indian kimberlite using inductively coupled plasma mass spectrometer (ICP-MS)

A method has been developed for the analysis of rare earth elements (REEs) in kimberlite samples using inductively coupled plasma mass spectrometer (ICP-MS). The samples were dissolved using sodium peroxide fusion and after appropriate dilutions the solutions were analyzed using ICP-MS. The paper presents the concentration of rare-earth elements as determined by ICP-MS in eight kimberlite samples from Central India. The method was validated using certified reference materials STSD-1 and STSD-2 from Canadian Certified Reference Material Project. The method detection limit of various REEs varies from 0.12 to 1.54?mg?kg^?1. The total REE concentrations range from 418 to 726?mg?kg^?1 and fall within the interval of those reported in the literature for kimberlites. Despite the marked difference in the REE contents, all the analyzed samples show similar REE patterns that resemble those for kimberlites. In order to compare ICP-MS results, the samples were analyzed using instrumental neutron activation analysis which is a reference method for determination of REEs in geological samples.